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Tensile strength and performance of the INDUO®-heavy-timber connector in combination with structural.. Steiniger, Markus 2003-12-31

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Tensile Strength and Performance of the INDUO®-Heavy-Timber Connector in Combination with Structural Composite Lumber and Douglas Fir by MARKUS STEINIGER Diplom-lngenieur (FH) Holzbau und Ausbau, [B.A.Sc] Fachhochschule Rosenheim, 2001 A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in FACULTY OF GRADUATE STUDIES Department of Wood Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA July, 2003 © Markus Steiniger, 2003 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver, Canada Date DE-6 (2/88) inoduo Abstract ii Abstract The INDUO-connection is a new steel-to-wood joint for highly loaded heavy-timber structures. Embedded in the end-grain of laminated timber beams, the special INDUO-connector is designed to transfer axial and transverse loads. Due to the weaker strength properties of solid wood perpendicular to the grain direction, the connection's capacity under transverse loading is comparatively small. Parallel to the grain, however, the connection is capable to transfer loads of up to 180kN and is thus predominantly suited for tension applications. Since the introduction to the European market in the Mid-90s, the INDUO-connection system has been mainly deployed in Post-and-Beam structures using softwood timber and Glulam as beam material. This thesis investigates the tensile strength and performance of the INDUO-connector in combination with different beam materials. Static tension tests were performed in two separate test series with a total of 99 specimens of different member cross-sections (100x100mm and 120x120mm), connector types (A and B) and beam materials (Microllam®LVL, Parallam®PSL, TimberStrand®LSL, thick Douglas-Fir plywood and Douglas-Fir lumber). In test series 1 all possible combinations of beam material, connector type and member cross-section were tested with a sample size of up to three, providing trends on strength properties and failure performance. For test series 2 it was decided to focus on fewer combinations with a larger sample size to create statistically more significant results on ultimate tensile strength and connection stiffness for the most advantageous setups. By modeling and calculating the INDUO-connection according to different international timber codes (German DIN1052-2000, European EC5, Canadian CSA 086.1 and US ASCE 16-95) as a bolted or tight-fitting dowel connection, characteristic tensile strength data was computed and compared with the characteristic values derived from the results of series 2. In terms of tensile strength and performance, TimberStrand®LSL presented the best test results, outperforming Microllam®LVL, Parallam®PSL and Douglas-Fir lumber, which showed significantly lower tensile strengths accompanied by brittle failure modes. Thick Douglas-Fir plywood was only examined in test series 1, presenting high tensile strength for larger beam-cross-sections, whereas smaller cross-sections failed brittely. inoduo Abstract iii The comparison of different design approaches for the INDUO-connection showed that based on the same connection model (dowel-type fasteners with inside steel plate) the Canadian timber code provided by far the most conservative design values, whereas all other codes presented significantly higher numbers relative to the Canadian code . The comparison of characteristic tensile strength properties generated from the test results and values derived from the different design strengths indicate all four timber codes have more or less similar results. inoduo Table of Contents iv Table of Contents Abstract ii Table of Contents v List of Figures viList of Tables xi Dedication xiAcknowledgements xiii 1 Introduction 1 1.1 Research Objective 5 1.2 Scope 6 2 Non-visible heavy-timber joints 7 2.1 Non-visible mechanical connections2.1.1 The BSB-system (Tight-fitting dowels)2.1.2 The SpikeTec-system (Embedded nail plate) 9 2.2 Non-visible composite connections 10 2.2.1 Glued-in steel rods 11 2.2.2 The TiSCo®-system 4 2.2.3 The BVD®-system 5 3 Materials and Methods 19 3.1 Materials 13.1.1 Microllam®LVL3.1.2 Parallam®PSL 21 3.1.3 TimberStrand®LSL 3 3;1.4 Douglas-Fir plywood 4 3.1.5 Douglas-Fir lumber 26 3.1.6 INDUO-connector (type A) 7 3.1.7 INDUO-connector (type B) 8 inoduo Table of Contents v 3.2 Methods 29 3.2.1 Scope of the test series 23.2.2 Connection design 31 3.2.3 Fabrication of test specimens 34 3.2.4 Experimental setup 7 3.2.5 Test procedure 39 4 Results 40 4.1 Test series I 1 4.1.1 Group I (TimberStrand®LSL & Douglas-Fir plywood) 43 4.1.2 Group II (Douglas Fir & Microllam®LVL) 47 4.1.3 Group III (Parallam® PSL) 50 4.2 Test series II 52 4.2.1 Performance 4 4.2.1.1 TimberStrand®LSL 54.2.1.2 Douglas Fir 6 4.2.1.3 Parallam®PSL 8 4.2.1.4 Microllam®LVL 60 4.2.2 Strength and stiffness 2 5 Discussion 8 5.1 " Evaluation of test results 65.2 Comparison of characteristic strength values 71 5.2.1 Connection Model 75.2.2 Determination of code design values 72 5.2.2.1 DIN 1052-2000 (draft) 5 5.2.2.2 EC5 (Eurocode 5) 76 5.2.2.3 CSA 086.1 7 5.2.2.4 ASCE 16-95 8 5.2.3 Characteristic strength values 79 5.3 Evaluation of connection stiffness with structural model 83 6 Conclusion and Recommendations 86 inoduo Table of Contents vi 7 List of References 88 8 Appendices 92 8.1 Photographic documentation 98.1.1 Manufacturing steps of test specimen 92 8.1.2 Test procedure 95 8.1.3 Failure modes 100 8.2 Calculations 11incduo List of Figures vii List of Figures Figure 1: Plan of connection 2 Figures 2 & 3: Assembly of a single-family house constructed with the INDUO-system 2 Figure 4: 3-dimensional roof truss 3 Figure 5: INDUO-system applied in 3-dimensional truss system 3 Figure 6: INDUO-connector and timber halves before assemblyFigure 7: Embedded connector; beam ready to be pressed in hydraulic press 3 Figure 8: INDUO-connector type A 4 Figure 9: INDUO-connector type BFigure 10: Manufacture of INDUO-Quarter Logs 4 Figure 11: BSB-joints in heavy timber truss 8 Figure 12: Scheme of BSB-connectionFigure 13: BSB-system applied in a roof structure of a spa 8 Figure 14: Footbridge constructed with BSB-connectionFigure 15: Close-up of SpikeTec-connection 9 Figure 16: Nail plates are set in placeFigure 15: SpikeTec-system applied in the roof structure of a supermarket 10 Figure 16: Roof truss system constructed with SpikeTec-connection 1Figure 17: Glued-in steel rod connection (Madsen) 12 Figure 18: Applications for glued-in steel rod connections (Madsen) 1Figure 19: Research conducted on glued-in steel rod connections 3 Figure 20: Sketch of test specimens (before grouting) 1Figure 21: TiSCo-connector: Sandblasted and grooved version 14 Figure 22: TiSCo-connector inserted in end grainFigure 23: Manufacturing steps of the TiSCo-connection 15 Figure 24a: Components of the BVD-system 16 Figure 24b: Different hanger sizes in various length configuration 1Figure 25: Manufacturing the BVD-connection ' 16 Figure 26: Knee joint with BVD-connection 17 Figure 27: Tower column with BVD-connection to foundation 18 Figure 28: EXPO-Roof with towers supporting the roof structureFigure 29: Manufacture of LVL 20 Figure 30: Close-up of LVLFigure 31: Manufacture of PSL 1 Figure 32: Close-up of PSL 22 Figure 33: PSL applied in heavy-timber structure (Forestry building, UBC) 22 inoduo List of Figures viii Figure 34: Manufacture of LSL 23 Figure 35: Close-up of LSL 4 Figure 36: Manufacture of plywood 5 Figure 37: Close-up of thick Douglas Fir plywood 2Figure 38: Close-up of Douglas Fir 26 Figure 39: Manufacture of sawn lumberFigure 40: Connector type A 7 Figure 41: Connector type B 28 Figure 42: Components of lower support 33 Figure 43: Lower support assembledFigure 44: Ring Side Plate 3Figure 45: Upper support 4 Figure 46: Plan of timber halves: a) type A -100 combination; b) type A - 120 combination 36 Figure 47: Plan of timber halves: a) type B -100 combination, screw-bond; b) type B - 120 combination 36 Figure 48: Experimental setup: MTS 810 with control system and test member 37 Figure 49: Test member 38 Figure 50: Upper support featuring a DCDT measuring device 3Figure 51: Connection failure modes 40 Figure 52: Group I: No failure for connector type B combinations 43 Figure 53: Group I: Severe bearing; a typical failure mode for connector type A combinations 4Figure 54: Load-displacement curves of TB-combinations 45 Figure 55: Load-displacement curves of TA-combinationsFigure 56: Load-displacement curves of XB-combinations 46 Figure 57: Load-displacement curves of XA-combinationsFigure 58: Group II: Splitting along the rows of holes; a typical failure mechanism of connector type B combinations 47 Figure 59: Group II: Bearing and relatively large displacements due to shear failure of connector type A combinations 4Figure 60: Load-displacement curves of DB-combinations 8 Figure 61: Load-displacement curves of DA-combinations 4Figure 62: Load-displacement curves of MB-combinations 9 Figure 63: Load-displacement curves of MA-combinations 4Figure 64: Group III: Bearing and tear-out of connector type A combinations 50 Figure 65: Group III: Connector type B combinations witness severe pin deformations or fracture 5Figure 66: Load-displacement curves of PB-combinations 51 ircduo List of Figures ix Figure 67: Load-displacement curves of PA-combinations 51 Figure 68: LSL: No damage observed at the pin holes 4 Figure 69: LSL: No deformations of the connector 5Figure 70: Load-displacement curves of TB-combinations 55 Figure 71: Load-displacement curves of S-TB-combinationsFigure 72: DG fir: Splitting along rows of holes 56 Figure 73: DG fir: Shear failure in the plane of the pins 5Figure 74: Load-displacement curves of DB-combinations 7 Figure 75: Load-displacement curves of S-DB-combinations 5Figure 76: PSL: Splitting along the rows of holes 58 Figure 77: PSL: Deformation of the connector pinsFigure 78: Load-displacement curves of PB-combinations 59 Figure 79: Load-displacement curves of S-PB-combinations )Figure 80: LVL: Splitting along rows of holes 60 Figure 81: LVL: Ripped-off pins - 6Figure 82: Load-displacement curves of MB-combinations 0 Figure 83: Load-displacement curves of S-MB-combinations 61 Figure 84: Different approaches to determine the connection stiffness 63 Figure 85: Classification of member setups according to tensile performance 69 Figure 86: Close-up of end grain: a) PSL; b) LVL; c) Douglas Fir; d) LSL 70 Figure 87: Connection model 71 / Figure 88: Plan of connection 3 Figure 89: Failure modes according to European Yield Model 74 Figure 90: Different test procedures to determine the embedding strength of wood and wood-based material; a), DIN EN 383-1993 b) ASTM D5764a-1997 80 Figure 91: Thalkirchen Bridge, Munich, Germany 83 Figure 92: Support with node and connected beamsFigure 93: Node in the truss system 8Figure 94: Connection setup of INDUO-connector in 3D-space truss beam 84 Figure 95: Cutting timber members to rough dimensions (Sliding Table Saw) 92 Figure 96: Planing of timber members to final width and thickness (4-Sided Planer) 92 Figure 97: Machining of rows of holes and V-groove by means of CNC-router 92 Figure 98: Machining of circular grooves (CNC-router) 9Figure 99: INDUO-connector ready to be embedded in machined timber halves 93 Figure 100: Circular grooves to accommodate Steel Side Plates 9Figure 101: Applying PVA-construction glue to both inside faces of the timber halves 93 Figure 102: Inserting the connector in V-groove 9Figure 103: Joining of both timber halves enclosing the connector 94 incduo List of Figures x Figure 104: Inserting the composite member into hydraulic press; Pressing time: 30 minutes 94 Figure 105: Alternative connection of timber halves with regular wood-screws 6x10 94 Figure 106: Setup of screwsFigure 107: Tapering of the test member to squared cross-section 100x100 and 120x120mm respectively (NC-shaper) 94 Figure 108: Specimen ready to be tested 95 Figure 109: Stacked members of different connector-material setups before testing 95 Figure 110: Specimen connected to upper machine support 9Figure 111: Steel Side Plates transfer applied load from the lower machine support to test member 95 Figure 112: Assembly of Steel Side Plates with 7/8-inch bolts 96 Figure 113: Close-up of steel rings sliding into circular grooveFigure 114: Steel Side Plates are pressed into grooves by means of regular clamps 96 Figure 115: Components of lower coupling: Distance plates and two 1-inch bolts 96 Figure 116: Lower coupling fastened 97 Figure 117: Specimen connected to test apparatus, ready to be tested 9Figure 118: Test apparatus consisting of test machine, control unit and PC 98 Figure 119: Unloading of heavy test member by means of a "mobile gallow" 98 Figure 120: Gallow in place to support the test member after being uncoupled 98 Figure 121: Disassembling of upper and lower couplings 9Figure 122: Tested type A and B specimens, 120x120mm, test series 1 99 Figure 123: Tested type A and B specimens, 100x100mm, test series 1Figure 124: Tested connector-type-B specimens, 100x100mm, test series 2 99 Figures125a-e: No failure observed with TB-member setups 100 Figures126a-b: Failure modes observed with TA-member setups 101 Figures 127a-f: Failure modes observed with XB-member setups 102 Figures 128a-c: Failure modes observed with XA-member setups 103 Figures 129a-g: Failure modes observed with DB-member setups 104 Figures 130a-c: Failure modes observed with DA-member setups 105 Figures 131a-g: Failure modes observed with MB-member setups 106 Figures 132a-d: Failure modes observed with MA-member setups 107 Figures 133a-f: Failure modes observed with PB-member setups 108 Figures 134a-c: Failure modes observed with PA-member setups 109 inoduo List of Tables xi List of Tables ( Table 1: Test variables 29 Table 2: Moisture content and density of tested specimens 40 Table 3: Analyzed data of test series 1 41 Table 4: Analyzed data of test series 2 52 Table 5: Statistics on ultimate load 6Table 6: Statistics on displacement at ultimate load 62 Table 7: Statistics on different 10/40- and 30/70-connection stiffness 64 Table 8: 5th percentile strengths of respective distributions 66 Table 9: Characteristic values of maximum tensile capacity 7 Table 10: 5th percentile of 10/40-stiffness 6Table 11: 5th percentile of 30/70-stiffnessTable 12: Example showing a step-by-step approach to determine characteristic values for tensile capacity 81 Table 13: Comparison of characteristic connection strength values 8Table 14: Calculation example on stiffness and displacement of INDUO-connector in 3D-truss beam 85 Table 15: RELAN data fitting of strength data set 110 Table 16: RELAN data fitting of stiffness data setTable 17: Calculation of characteristic strength values; PSL 111 Table 18: Calculation of characteristic strength values; Douglas Fir 112 Table 19: Calculation of characteristic strength values; LVL 113 Table 20: Calculation of characteristic strength values; LSL 4 dedicated to my mother Anne inoduo Acknowledgements xiii Acknowledgements I would like to express my greatest thanks to my supervisors Dr. Helmut Prion and Dr. Frank Lam for their advice and guidance during my Master's program and this research. Their comments and constant support meant a great help to me and contributed very much to the successful completion of the project. I also would like to thank Robert Fiirst, Tom Wray, Robert Myronuk, George Lee and Emmanuel Sackey of the Department of Wood Science and Harald Schrempp of the Department of Civil Engineering for their great practical help in the preparation process of the test series. Their dedication helped to carry out the research in a very smooth and effective manner. I would like to thank especially Bruce Craig of TrusJoist, a Weyerhaeuser Business and Gordon White of Ainsworth Lumber Co. for providing the Microllam®LVL, Parallam®PSL, TimberStrand®LSL and Douglas-Fir plywood, respectively. Without their generous donations of material and their technical support, the research would have been a lot more difficult. For comprehensively supporting the research and supplying the INDUO-connectors, I would like to express my special gratitude to Paul Reichartz and his team of INDUO. jnoduo Introduction 1 1 Introduction Carpentry in Europe looks back on a very long tradition and history. Over centuries craftsman skills have been improved and passed on from one generation to the next. In the past a carpenter meant more than just manufacturing wooden structures; via their craftsmanship carpenters united the work of engineers, architects and contractors into one person. Until the end of the 18th century, being universal experts, they acted as general contractors. The industrial revolution changed the traditional construction habits. Especially the Central European countries witnessed a substantial shift from wood to steel, concrete and brick as major building materials. This development caused a severe depreciation of the carpenter's craftsmanship. Despite their knowledge and skills, carpentry's time and cost intensive manual-labor could not compete with the upcoming industrialized and engineered construction technology. Carpentry lost its dominating role both in the design process and the construction. Since then, carpenters gradually limited their field of work to the manufacturing of roof and truss structures. Until the 1980s, wood as construction material remained relatively dormant. In the last two decades, however, especially in Austria, Germany, and Switzerland, an increasing environmental consciousness changed people's attitude towards the 'established' and 'old' construction materials. Demanding a healthy and 'environmentally friendly' as well as a comfortable and cozy home, more and more willing homebuilders decided to use wood for the construction of their new houses. Furthermore, public authorities supported the use of wood for commercial as well as public projects. With the renaissance of wood as the most natural of all building materials, the old carpenter's skills were again in great demand. In addition, computer-controlled woodworking machinery enabled carpenters to manufacture complex and labor-intensive wooden structures at a competitive price level. Compared to North America, building your own house in Europe is a very costly endeavor. Contributing with their own labor force, many homebuilders reduce construction costs by resorting to do-it-yourself (DIY) kits. For this reason, manufacturers of prefab houses or building components offer a variety of both hardware - structural components - and service - construction of the house up, to various degrees of completion. Depending on the skills of the homebuilder, all the finishing work can be done by DIY style. Due to good workability, wood and wood products are widely used in this area. inoduo Introduction 2 In the early 1990s, Paul Reichartz, a German businessman and consultant, came up with the idea to provide both carpenters and DIY-homebuilders with a simple and affordable state-of-the-art construction system, while meeting all performance and code requirements and satisfying customers' demands. After years of development and adjustment, in 1995 the INDUO-connection and construction system was introduced in the homebuilding market. INDUO® is a contemporary heavy-timber system. It consists of precisely prefabricated, easy-to-assemble wooden members of varying cross-section and length, connected to standardized steel nodes. These basic elements can be used to build up post-and-beam frames with varying configurations. These building elements are also well suited for highly loaded timber structures, such as 3-dimensional space trusses. Figure 1: Plan of connection Figures 2 & 3: Assembly of a single-family house constructed with the INDUO-system inoduo Introduction 3 Figure 4: 3-dimensional roof truss Figure 5: INDUO-system applied in 3-dimensional truss system Consisting of two timber halves and two special wood connectors, the primary framing members can be considered as composite beams. Before gluing the wooden halves together, they are specially machined to accommodate the cast steel connector. The connector element itself features a set of tapered spikes and has a female thread connection at both ends, which can be bolted to a variety of nodes or brackets. Located along the center-line of the member, the connector is designed to transfer axial and transversal loads. A common wrench is the only tool necessary for the assembly. Thus, both simple and complex structures can be erected fast and precisely. Figure 6: INDUO-connector and Figure 7: Embedded connector; beam ready to be timber halves before assembly pressed in hydraulic press inoduo Introduction 4 Since 1995 various research projects have focused on the manufacturing process of the joint with less emphasis on load carrying capacities (Fuhrer 1997). In a small test series Guldenpfennig (1996) proofloaded 12 INDUO-connections with Spruce gluelam up to 100kN. Only one of the specimens failed. In 2001, the original connector (type A) was superceded by an advanced version. The modified shape of the new connector (type B) allowed the capacity of the connection to be calculated according to the German code DIN 1052-1988 as a Tight-Fitting-Dowel joint (BlaB 2001). Tests to verify this design and calculation model were not conducted. Figure 8: INDUO-connector type A Figure 9: INDUO-connector type B In the past, the basic elements were made with solid softwood - mainly Spruce and Fir. Manufacturing the so-called "Quarter Logs" with exposed edge grain and pith forming the member corners allows the connector spikes to penetrate into the flat grain portion of the log. Visually more attractive, the Quarter Log can be made from small logs, possibly even peeler cores. Round timber Ripping into Rotation Milling Lamination Quarters Figure 10: Manufacture of INDUO-Quarter Logs inoduo Introduction 5 Being a high-performance connection method, the INDUO connector could be cost-effectively applied in heavy-timber construction with structural composite lumber. Since little is known about the connection's behavior in combination with such engineered wood products, composites like Laminated Strand Lumber (LSL), Parallel Strand Lumber (PSL) or Laminated Veneer Lumber (LVL) have so far not been considered as possible substitutes for solid wood. The intention of this Master research project was to gain more specific information on the joint's tension behavior with emphasis on ultimate strength and failure mode. As this connector is primarily suited for tension application, it was decided that testing of the INDUO-member deployed as beam elements, where transverse shear will be the dominant load, would not be done. 1.1 Research objective Officially introduced in Germany, the INDUO®-system has been successfully marketed in many European countries. The system has been gradually improved to respond to various customer demands. INDUO's future goal is to enter the North American marketplace. Considering different construction standards and techniques as well as a different set of priorities, it is essential to adjust the system to North American demands and requirements. Concerning the adaptation of INDUO, the following issues are of substantial interest: • Investigation of connector type B's tensile behavior: - Mechanical properties (strength and stiffness) - Failure mode - Calibration of rational calculation model (BlaB 2001) • Influence of different member configurations on tensile behavior; Comparison of connector type A and type B with: - Beams built-up with different wood species (solid wood and wood composites) - Different methods of bonding the two member halves: screwed or glued - Members of different cross-sections inoduo Introduction 6 1.2 Scope A comprehensive test program, considering all the above-mentioned parameters and providing a sufficient sample size to create statistically significant data, was deemed to be beyond the scope of a Master thesis. Therefore, it was agreed to split the project into two separate test series, each focusing on different aspects. In series 1, beam members of all the possible combinations of material, connector type, member cross-section and lamination type were tested under tensile loading. Up to three specimen for each individual combination are meant to provide'general information and performance trends. Data assessment and experiences of series 1 then served as the basis for a detailed and more accurate investigation of one combination. With a sample size of up to 10, statistically more significant results for ultimate tensile strength were determined. This test series would then be used to calibrate an analytical model for calculating the tensile capacity of typical connections. inoduo Non-visible heavy timber joints 7 2 Non-visible heavy-timber joints Comparing North American and European practices, the design approach of timber joints is significantly different. Since the 1970s, European architects and structural engineers have more and more tended to 'hide' or embed timber connections for esthetic and / or fire protection purposes, whereas contemporary North American heavy-timber design still prefers to expose the connection. Responding to the trend for non-visible joints, numerous new connection types have been developed in Europe. With improved mechanical properties and advanced performance, these innovative connections have been widely applied in various timber structures. Being embedded in a composite beam member, the INDUO-connector, which is the focus of research in this Master thesis, represents one of the above-mentioned non-visible timber joints. The following sections give an overview of various other non-visible connector systems. 2.1 Non-visible mechanical connector systems Most of the joints used in timber structures are mechanical connections. Being exposed, simple fasteners like nails, bolts, drift pins and lag screws, as well as advanced fastener types like shear plates, split rings, truss plates, sheet metal connectors and glulam rivets often present a problem with esthetic and fire protection demands. Embedded or hidden connectors, however, typically meet these requirements. Mechanical connectors, when proportioned carefully, can meet demands for high ductility which is important for equal load distribution and energy absorption. 2.1.1 The BSB-system (Tight-fitting dowel connection) Tight-fitting dowel connections consist of high-quality steel dowels and embedded steel plates. Driven into undersized pre-drilled holes, the dowels are kept in place by friction. In addition to being esthetically more pleasing, tight-fitting dowels are further distinguished from bolted connections by higher strength values and better failure performance. The dowel press fit prevents initial slip and guarantees a stiff connection as well as a more uniform load distribution. inoduo Non-visible heavy timber joints 8 Figure 11: BSB-joints in heavy timber truss Figure 12: Scheme of BSB-connection Requiring highly accurate fabrication, Computer Numerically Controlled-equipment more and more substitutes the time-consuming and difficult manual labor of precisely drilling the dowel holes and machining the slots for the steel plate. Manufacture and assembly of the joint is mostly done in the shop under controlled conditions. Depending on the size, smaller components of the structure are prefabricated, then brought to the construction site and finally completed by connecting a limited number of joints. During fabrication, transport and assembly, moisture fluctuations of the wood must be strictly avoided. The BSB-connection is a highly optimized tight-fitting dowel connection that was developed in Switzerland (Mischler 2000). It is officially approved in many European countries and has been applied in many heavy-timber structures. Figure 13: BSB-system applied in a roof Figure 14: Footbridge constructed structure of a spa with BSB-connection irvoduo Non-visible heavy timber joints 9 2.1.2 The SpikeTec-system (Embedded nail plate) Invented by MERK1 and officially approved in Germany (DIBt2 2002), the SpikeTec-system is a further development of the truss-plate connection. It is mainly applied for large trusses and is typically used with composite structural lumber. The connection consists of the SpikeTec-connector - a steel plate with a double-sided set of spikes welded perpendicular to its surface - sandwiched between a pair of timber members. Figure 15: Close-up of SpikeTec-connection Figure 16: Nail plates are set in place The steel plate is 10mm thick; the spikes have a length of 50mm and a diameter of 5mm. LVL and glued-laminated timber are commonly used for the truss members. In the manufacturing process, the nail plate is pressed into the flanging side members. To meet higher fire protection requirements, both timbers have to be countersunk by 5mm in the nail plate area. The wood thus completely encloses the connector. Optimized design enables the SpikeTec-connection to carry 50% more load parallel to grain than a conventionally bolted joint of the same size. Due to compact joint dimensions and reduced member cross-sections, the construction of large timber trusses has become competitive with structural steel. 1 MERK Holzbau, Aichach, Germany. Leading contractor for heavy-timber constructions 2 DIBT: Deustches Institut fur Bautechnik (German Institute for Construction Technology) irroduo Non-visible heavy timber joints 10 2.2 Non-visible composite connector systems Unlike many mechanical connectors, composite joints with Epoxy, Resorcinol or non-shrink grout glued-in steel components, provide high stiffness and strength, low tolerances, easy fabrication, and for completely embedded connectors systems, good fire protection. The main disadvantages are brittle failure modes of the glued connection and deterioration of strength properties due to climate changes and poor quality of the glue bond. While glued wood-to-wood connections are common in traditional joinery, larger structures have typically relied on mechanical fasteners. This is mainly to facilitate construction and / or assembly on site. The advantage of high-performance glued incduo Non-visible heavy timber joints 11 connections can be combined with mechanical on-site connection methods by gluing metal connectors to the wood. Failure modes can then also be controlled by assuring a weak link in the steel element. 2.2.1 Glued-in steel rods In the past 30 years several researchers have investigated means of transferring high loads from wood members to steel rod elements. In the 1960s and '70s Scandinavian engineers (Riberhoit 1988) conducted initial research on inserting steel rods into predrilled and oversized holes filled with Epoxy or Resorcinol glue. Placed parallel to grain, this composite joint was the first successful application of gluing steel to timber. In Russia (Turkowskij 19913) ribbed steel bars were glued perpendicular to the grain in places where the Glulam was subjected to excessive bearing forces. Later, reinforcement bars were inserted at a 30° angle to reinforce the timber members for high shear stresses. In the late 1980s, extensive research was conducted at UBC (Madsen 1998), to develop a reliable glued-in steel rod connection. Madsen phrased guidelines to meet state-of-the-art performance requirements. They are: - High Strength - High Stiffness - Avoid brittle failure - Tolerate reverse loading - Loads transferred via specified path - Simplicity of design - Ease of manufacturing - Construction friendly - Attractive appearance - No field gluing - No field welding - Provide for corrosive environment (if needed) - Fire protection - MC of wood members less than 15% - Cost 3 Research had begun already in 1975, however, remained unknown for the rest of the world till 1989, because publications were in Russian. r irxxJuo Non-visible heavy timber joints 12 Investigating the performance of the wood to glued-in steel rod connection in general, in terms of strength, stiffness, different sizes and lengths of the rods, as well as the joint's behavior with rods perpendicular and at an angle to the grain, Madsen came up with a basic connection design suitable for various applications. Recess for plate Figure 17: Glued-in steel rod connection (Madsen) Anchor plates with pre-welded rods on one side are inserted in epoxy glue filled holes of the timber member. In the structure, these composite members are then connected to each other with bolts. Engaging a larger portion of the cross-section, the use of angular rods was found to increase load-bearing and shear capacities of the wood member. Figure 18: Applications for glued-in steel rod connections (Madsen) inoduo Non-visible heavy timber joints 13 f Madsen Canada Buchanan Fairweather New Zealand A Turkovskij Russia Riberholt Denmark Figure 19: Research conducted on glued-in steel rod connections Many researchers worldwide have raised concerns about the sensitivity of the epoxy glue joint to climatic changes. The loss of strength and stability due to changing moisture contents and temperatures, as well as a required minimum temperature for the adhesive reaction, limits the use of epoxy for outside applications or structures with strict fire protection requirements. Kangas (2000) conducted fire resistance tests of epoxy glued-in V-form steel rod connections. To avoid premature failure of the joint, he found that all fire exposed steel parts have to be covered with rock wool and steel sheets. Due to severe loss of strength when heated above 50°C, epoxy glue was substituted by cement grout (Buchanan and Eiststetter 2000). While easy to handle, inexpensive and fire resistant, however, cement grout's poor adhesion to the timber represents a major problem, therefore requiring a mechanical bond. Reinforcement with pins and screws, driven into to the wood member before grouting, is one way to create a strong connection with good fire resistance. Figure 20: Sketch of test specimens (before grouting) (Buchanan) inoduo Non-visible heavy timber joints 14 The TiSCo®-system Building on the knowledge of more than 30 years of research experience in the field of glued-in steel connections, the German TiSCo®-system (Timber-Steel-Connector) represents a new type of composite connector. The tubular shape of the connector, providing a larger surface area to carry load and the use of an easy-to-handle, strong and temperature-tolerant vinyl-ester based compound mortar distinguishes this connector system from most other glued composite connections. The connector, which consists of a mild steel tube (125mm long, 48mm outer diameter and 3mm wall thickness) and a steel plate welded to one end, is inserted into the end grain of a wooden member. Featuring a threaded hole (M16), the steel plate acts as connector head, which can easily be connected to adjacent elements of the structure. To provide enhanced adhesion, the surface of the tube is sandblasted or ribbed. In addition, four longitudinal slots over most of the tube's length are meant to reduce residual stresses due to deformations of the wood. Figure 21: TiSCo-connector: Sandblasted and grooved version Figure 22: TiSCo-connector (Schreyer) inserted in end grain (Schreyer) The connection is manufactured in three steps: 1. Drill a circular hole, including a 20mm countersink to accommodate tube and head of the connector 2. Inject mortar into the hole and 3. Insert the connector with a twisting action, distributing the viscous mortar all over the glue splice. irxxJuo Non-visible heavy timber joints 15 After a short hardening time of approximately 10 minutes, the squeezed-out excess mortar can be removed; 1 hour later, loads can be applied. Figure 23: Manufacturing steps of the TiSCo-connection (Schreyer) Bathon and Schreyer (2000) investigated strength and stiffness properties of the TiSCo-connector. Under tensile loading, the connection fails abruptly with a withdrawal of the connector along the mortar surface. Under compression, after a failure of the mortar bond, wood compression causes an increase of loading capacity with ductile failure characteristics. Preliminary research showed that exposure to changing climates may result in a reduction of the tensile load capacity of the connection. Although, extensive research was conducted, TiSCo has never been tested and used in full-size timber structures, thus remaining a prototype. 2.2.2 The BVD®-system Successfully utilized in numerous heavy-timber structures, the BVD-system, developed and marketed by German engineer Peter Bertsche, provides high connection strength and stiffness properties in the longitudinal direction of the loaded member. The BVD-system consists of a cylinder-shaped main connector hanger with inside thread inserted into the end grain of a member, a large number of drift pins located perpendicular to the connector's longitudinal axis and a non-shrink cement grout that compounds wood and inoduo Non-visible heavy timber joints 16 steel parts creating a composite joint. The recess for the main connector as well as the holes that accommodate the drift pins are predrilled and generously oversized to provide enough play for a uniform distribution of the cement grout poured into the voids between wood and steel parts. Figure 24a: Components of the BVD-system (Bertsche) Figure 24b: Different hanger sizes in various length configuration (Bertsche) The following set of pictures show the manufacture of the BVD-Joint: Figure 25: Manufacturing the BVD-connection (Bertsche) inoduo Non-visible heavy timber joints 17 The four steps of manufacturing and installing the BVD-joint are as follows: 1. Drill the pin holes. 2. Drill the large main connector hole in the end-grain of the member. 3. Insert connector hanger first, followed by the drift pins that interlock with the connector. Adjust and fix position of the connector. 4. Cover the surface of the member with plastic foil to protect the wood from being stained and pour cement grout into special feed openings. The grout is cured after 12 hours. Ready to be installed in the structure, however, the member is not to be fully loaded for another 12 hours. After 28 days the grout is completely cured, providing the maximum strength. The BVD-system has been widely applied in many heavy-timber structures all over the world. Over 250 major projects, including wooden bridges, large span roof structures and various custom timber constructions have been built using the high-strength BVD-connector. In addition, in the area of reconstruction and renovation of historic timber structures the system recently found a further field of application. fl Figure 26: Knee joint with BVD-connection (Bertsche) inoduo Non-visible heavy timber joints 18 For the largest timber structure ever been designed and constructed, the EXPO-Roof built for the world exposition in Hannover, Germany in 2000, the BVD-system was applied in one of the main joints that connect the tower columns with the foundation of the structure. Due to the size and the number of the column members, the BVD-joints were processed on a CN-controlled machining center. drift pins Bolts connected to main member Figure 27: Tower column with BVD-connection to foundation Figure 28: EXPO-Roof with towers supporting the roof structure inoduo Methods and Materials 19 3 Materials and Methods Chapter 3 describes the methodology of the research work on investigating the tensile performance of the INDUO-connector. As mentioned in the introductory chapter, limited knowledge on the strength and performance of both connector type A and type B and a set of various problems resulted in a subdivision of the practical research into two test series. Section 3.1 specifies the different wood materials used in the construction of the test members, including how these wood products are manufactured, and their material characteristics. Furthermore, section 3.1 introduces the different connector types. Section 3.2 describes in detail the scope of the research, the connection design, the fabrication of the test specimens and the set-up of the test apparatus. 3.1 Materials Microllam®LVL, Parallam®PSL, TimberStrand®LSL, Douglas-Fir plywood and Douglas-Fir lumber are the different wood materials used in this research project. 3.1.1 Microllam®LVL Laminated Veneer Lumber is an engineered wood product created by layering dried, graded and adhesive-coated wood veneers into blocks of material. Rotary-peeled on a lathe, the veneer is typically produced in thicknesses of 2.5, 3.2, and 4.2 mm. The adhesive used in Microllam®LVL is phenol formaldehyde, continuously applied to the veneer sheets by passing under a glue-curtain. Layered with the grain running in the lengthwise direction and specifically located in the veneer block to assure optimized strength properties, the laminations are cured in a heated press, fabricating a continuous billet. After exiting the press, the billet is sawn to standard dimensions, either 610 mm or 1220 mm wide and 19 mm to 89 mm thick and is finally stored to cool down. Dependent on customer orders, stocked LVL is ripped and cut to the required length in a separate line. irxxluo Methods and Materials 20 Veneer End Cutting ,-"~..a Ultrasonic -"^i Grading Shipping Grading ^jliyiicrollarti Figure 29: Manufacture of LVL (TrusJoist) Figure 30: Close-up of LVL With a consistent moisture content, LVL is virtually free from warping and splitting and can be easily worked using conventional woodworking tools. Compared to common lumber products, due to defect removal and dispersal, LVL as a solid, highly predictable and uniform wood product offers higher reliability and lower variability. For the research project LVL of grade 1.9E was used. One important benefit of LVL is that the veneering and gluing process creates large timbers from underutilized species of small trees. Besides the most common species Douglas Fir, Southern Pine and Spruce, in North America, Aspen and Yellow Poplar are increasingly being used. irroduo Methods and Materials 21 3.1.2 ParallanTPSL Representing a more recent development of structural composite lumber, Parallel Strand Lumber is another lengthwise oriented structural wood product, created by layering dried, adhesive-coated veneer strands parallel into blocks of material. Similar to the manufacture of LVL, the veneer is typically produced from Douglas Fir, Southern Pine or Yellow Poplar and either rotary-peeled to a veneer ribbon of 2.5 and 3.2mm thickness at the plant or purchased and delivered to the plant. The adhesive used in Parallam®PSL is resorcinol or phenol formaldehyde with a small admixture of wax to avoid moisture absorption of the composite. In the manufacturing process veneer is clipped to strands between 12.5 to 25mm width and up to 2.4m length. In a sorting machine strands shorter than 300mm are removed. After being coated with adhesive in an immersion bath, the strands are dried and then passed through a distribution system, where density and strength of the finished product is set by controlling the mass flow. Being layered and aligned approximately parallel to the product axis, the strands are gathered in a conveyor hutch to form a continuous billet of required mass per length. The strand mat is slowly fed into the press, which applies pressure for densification and cures the adhesive using microwave energy. Figure 31: Manufacture of PSL (TrusJoist) inoduo Methods and Materials 22 After cooling, finished billets of up to 279 x 483 mm in cross-section are ripped, cut and sanded to required dimensions. For handling reasons, the billet is cut to lengths of up to 22m. Because it is a continuous process any length is theoretically possible. Finally, the end grain of each finished member is treated with a sealant to avoid moisture absorption. Figure 32: Close-up of PSL Figure 33: PSL applied in heavy-timber structure (Forestry building, UBC) Besides its good workability and high strength, the unique and appealing parallel grain structure of PSL satisfies esthetic demands and is often left exposed as a design element. Independent of the wood species of the strands, PSL is generally provided in a 2.0E grade. In terms of recovery and efficiency, the manufacture of Parallam®PSL utilizes 64 percent of a log, whereas traditional sawmilling processes convert only 40 percent of a log into lumber. irvoduo Methods and Materials 23 3.1.3 TimberStrancTLSL Laminated Strand Lumber is one of the latest developments in engineered wood product technology. It is also a strand-based product with fiber orientation slightly more random than PSL. In the manufacturing process, around 75 percent of a log of low-density hardwood species such as Yellow Poplar, Aspen and Cucumbertree is utilized. The adhesive used in TimberStrand®LSL is polymeric diphenylmethane diisocyanate (MDI) with a small admixture of wax to avoid moisture absorption of the composite. LSL is created by cutting the log into fine strands of 0.75 to 1.3mm thickness, roughly 25mm width and up to 300mm length. After drying and removing short pieces, the strands are conveyed to blenders where they are coated with adhesive and wax. Aligning the strands approximately parallel to the product axis, a 2.4 m wide continuous mat of specified mass is formed and cut to the appropriate pressing length. In the press the mat is densified and cured with injected steam, creating a composite with minimal density variation throughout its thickness. After exiting the press and cooling, the LSL billets with a rough size of up to 140mm thickness, 2.4m width and 11m length are sanded, ripped and cut to final dimensions, for structural material ranging from 32mm to approximately 100mm thickness. Strander Figure 34: Manufacture of LSL (TrusJoist) ircduo Methods and Materials 24 Although LSL is manufactured as panels, it is mainly used as linear elements, such as rimboards and studs. In terms of manufacturing, LSL is similar to Oriented Strand Board (OSB), except that OSB is conventionally hot pressed and LSL strands are longer and more-or-less parallel aligned, thus enhancing bending and axial strengths in the main direction. LSL is available in 1.3E, 1.5E and 1.7E grades. 1.5E grade was used for the research project. 3.1.4 Douglas-Fir plywood Plywood and LVL were originally developed in the 1930s for the manufacture of wooden airplane propellers and other high-strength aircraft parts. Since the 1950s as a substitute for solid wood sheathing, particularly in North America, plywood rapidly advanced to a highly deployed construction material. Although losing much of its market share to OSB, it remains one of the most important engineered wood products. The fabrication of plywood is similar to LVL, except that the grain direction of sequential veneer sheets is alternated and the layer set-up is symmetrical to the centerline. Dependent on structural or non-structural, exterior or interior application, different plywood grades are available. Typically Douglas-Fir or other softwood veneers and waterproof formaldehyde adhesives are used to build up the panel. In the manufacture, plywood panels are produced to sizes of up to 6 x 12m, then ripped and cut to standard dimensions of 1.2 x 2.4m; thicknesses range from 12.5mm to 38mm. inoduo Methods and Materials 25 Veneer lathe Venoer cutter Dryer •Veneer sorting for inner and outer plies Glue application Panel layup Assembled panels placed between heated platens in press _^L/~^>C Ed9e trimmir,g. patching, r - sanding and grading Bundling and shipping Figure 36: Manufacture of plywood (CWC) For the research project plywood of 50 and 60mm thickness was needed. Since standard plywood is limited a maximum thickness of 25.4mm, a set of one 12.5mm and two 19mm as well as a pair of two 25.4mm thick panels respectively were glued-laminated in the shop to build up the required panel dimension. Providing grade A on both faces and grade C1 for all inner plies, the 12.5mm, 19mm and 25.4mm thick panels consisted of 5, 7 and 9 cross-plies, respectively. Figure 37: Close-up of thick Douglas-Fir plywood incduo Methods and Materials 26 3.1.5 Douglas-Fir lumber Contrary to Europe, where timber is individually cut to customer demands, in North America sawmills mostly produce standard dimensions. In addition, dimension lumber sizes are expressed in nominal imperial units. A nominal 2x4 lumber member (pronounced 'two-by-four') for example has a cross-sectional area of 38 x 89mm. For the test specimen manufacture nominal 3x6 Douglas-Fir lumber (64 x 140mm) was directly purchased from a sawmill, since building material </////' /// ////muttfm suppliers do not carry larger lumber dimensions in \\\\\Hwr " 5 /if stock. Internally specified as 'cross-arm grade' the Figure 38: Close-up of Douglas Fir rough-sawn lumber is considered to be of equal quality as 'No. 1 and better' grade. The lumber was delivered with an average moisture content of 26% and had to be conditioned to 13% MC in one of UBC's drying kilns. Green chain Surfacing Grading Sorting • Log deck Bull chain from mill pond Headsaw Slab Shipping or further manufacture Edger saw Edgings Trimmer saws Trimmings Kiln dry (optional) Figure 39: Manufacture of sawn lumber (CWC) incduo Methods and Materials 27 3.1.6 INDUO-connector type A According to EN1562, connector type A consists of malleable cast iron of EN-GJMW-400-5 grade with a characteristic ultimate tensile strength fuk = 360 N/mm2 and a characteristic yield strength fy,k = 200 N/mm2. The fabrication process is as followed: 1. Casting of connector according to standard methods 2. Unloading of casting mould and cooling of member 3. Brushing and deburring 4. Sandblasting 5. Tapping of inside-thread 6. Galvanizing The solid connector body has a rhombic cross-section, featuring a set of 64 12mm long spikes, arranged in 4 rows of 8 spikes on either sides as well as two holes at both ends with an inside thread of 20mm in diameter (M20). The spike rows are offset by half the spike spacing in the longitudinal direction. With a total length of 213mm, the standard connector weighs approximately 1.3kg. According to technical specifications, dimension tolerances range around +/-0.5mm. In reality, longitudinal tolerances of up to 5mm were observed. This posed some challenges in the fabrication process of the beam element, as the precisely machined hole lines could not accommodate connectors with such large dimensional deviations. For this reason about 20% of the connectors could not be used. 15 , 25 . 25 '25 25 25 ,. 25 ,. 25 .. 23 n—i—i ri— I • •- o 0- -o o 0- o o a 0 o - < ••--•-^Or---- o «' -o 0 0 o 0 ©-a 0 o • o _— -o - - a-28 25 25 [ 25 25 25 25' Figure 40: Connector type A irvoduo Methods and Materials 28 3.1.7 INDUO-connector type B Being a further development, connector type B differs from type A in shape and material. Type B consists of spherical cast iron of EN-GIS-500-7 grade, defined in EN1563 with a characteristic ultimate tensile strength fUik = 500 N/mm2 and a characteristic yield strength fyk = 320 N/mm2. Weighing approximately 1.7kg, the standard connector has a total length of 247.8mm. The manufacturing process is the same as for type A. Comparing both type A and B, the shape of the main body is similar, whereas form and number of the load-bearing spikes was significantly modified. The 64 small spikes were substituted by 2 rows of 6 33mm long dowel-like pins on both sides. ^ ^ ® ^ A Figure 41: Connector type B Based on a calculation model which classifies the INDUO-connection as 'tight-fitting dowel joint with embedded steel plate these refinements in shape and material assured the connector behavior commensurate with analytical models used for design equations. This provides design engineers with a rational calculation model and therefore permits the use of the connector without special certification testing. incduo Methods and Materials 29 3.2 Methods 3.2.1 Scope of the test series To cover all the possible combinations of variables for the test specimens, considering two different connectors, as well as various dimension, lamination and material types, 40 different member types would be required (Table 1). To have a reasonable sample size of 10 per combination, 400 specimens would have to be tested. Material Connector Cross-section Lamination Douglas Fir Type A 100 x 100mm glued-laminated Douglas-Fir plywood Type B 120 x 120mm screw-bonded Microllam®LVL Parallam®PSL TimberStrand®LSL Table 1: Test variables To keep the testing program within the budgetary limitations, the total number of test specimens was set to 100 members. It was decided to investigate the different member combinations in two separate test series, gaining basic information on general connection behavior first and then focusing on one particular combination. To keep track of the various set-ups, a member code indicates important parameters: (S-) MA1-100 The first character (MA1-100) specifies the material: M for Microllam®LVL P for Parallam®PSL T for TimberStrand®LSL D for Douglas-Fir X for Douglas-Fir plywood (50 & 60mm) inoduo Methods and Materials 30 The second character (MA1-100) indicates the connector type: A for Type A B for Type B The last number (MA1-100) stands for the member cross-section: 100 for 100x100 mm 120 for 120x120 mm The first numerical character (MA1-100) indicates the sequential numbering of the specific member combination. The prefix S (S-MA1-100) indicates that the specimens' timber halves are connected by screws; instead of glued. In test series 1 only glued-laminated specimens were tested with a sample size (in brackets) of 2 and 3, respectively. These combinations are: MA-100(2) MA-120(2) MB-100 (2) MB-120 (3) PA-100(2) PA-120(2) PB-100(2) PB-120 (3) TA-100(2) TA-120(2) TB-100 (2) TB-120 (3) DA-100(2) DA-120(2) DB-100 (2) DB-120 (3) XA-100(2) XA-120(2) XB-100 (2) XB-120 (3) A small number of screw-laminated specimens were tested as a side study: S-TA-100, S-TB-100, 1 member each The total number of specimens for test series 1 was 47. Test series 1 was meant to point out performance trends of different member set-ups as well as to provide information for a better understanding of how individual parameters may influence the tensile strength and the failure mode. Based on the data being assessed from series 1, further considerations in terms of gathering more applied results led to more focused research on one promising combination in series 2. Since the self-made thick plywood does not represent an officially approved construction material and the manufacture of connector type A was recently stopped, although providing interesting data in series 1, both components were ircoduo Methods and Materials 31 excluded from further research. In addition, it was agreed to focus on the smaller cross-sectional member dimension - 100x100mm. In general, the manufacture of screw- or nail-laminated wood members does not require product certifications, such as glue permits. To facilitate the fabrication process, the use of screws to bond the timber halves is therefore a promising alternative to the traditional production of the INDUO-beam and was thus included in a side study in test series 2. In conclusion, it was decided to examine the following combinations: S-MB-100 (5) MB-100 (8+2) S-PB-100(5) PB-100 (8+2) S-TB-100 (5) TB-100 (8+2) S-DB-100 (5) DB-100 (8+2) The total number of tests in series 2 was 52. Considering previously tested specimens from series 1, the sample sizes for glued-laminated and screw-bonded members were 8 and 5, respectively. In summary, for both series, 99 test specimens were built and tested with 78 type B and 21 type A members. 3.2.2 Connection Design Performance and strength of wood-to-steel connections is significantly governed by the spacing and the end distances of fasteners, as well as the dimensions of connected members. Embedded in the end grain of the composite member, the position of the INDUO-connector and its first pair of pins and spikes respectively was set to 10d from the loaded edge, resulting in 80mm end distance for connector type B and 50mm for type A. The pin spacing is predetermined by the geometry of the fastener itself. Connector type A: The connector body features four staggered rows of eight spikes on each side. The spacing of the spikes in the lengthwise direction is 25mm and 10mm in the transverse direction. Due to significant fabrication tolerances, the connector and its tapered spikes, 12mm long and 5mm in average diameter, require largely oversized holes (d = 7 - 8mm). inoduo Methods and Materials 32 Initial slip of the connection is reduced in the assembly process by simply tightening the connecting bolt. The member cross-section is limited to a minimum of 80 x 80mm. Connector type B: Instead of a staggered alignment, the 33mm long pins, attached to both sides of the connector in two rows of six pins each, are arranged in an orthogonal matrix. The spacing in the lengthwise direction is 40.2mm and 25mm in the transverse direction. Precisely manufactured, type B's tapered pins (davg = 8mm) are designed to match accurately predrilled tapered holes, creating a press fit and thus eliminating initial slip. To transfer applied loads, a standard metric bolt (M20) of steel grade 8.8 (640 N/mm2 yield strength) is typically used to join the connector with other structural elements. In the research project M20-bolts of the best available grade 10.9 (900 N/mm2 yield strength) were utilized, providing a maximum tensile load capacity of 176kN according to EuroCode3. Due to various considerations, it was decided to install the INDUO-connector only at one end of the test member, thus requiring an appropriate support at the opposite end. Since well-founded data on the connector's ultimate tensile strength is not available and preliminary information on performance and strength was needed to design the opposite support, a single tension test with two type B connectors installed at both ends of an LVL-member was conducted. Failure occurred in one joint at a load of 127kN. Considering a stronger material to fail at a higher load level and desiring the test member to fail around the INDUO-connection, an opposite support system had to be strong enough to resist at least 200kN. Shear plate and split ring connections are known for high load capacities, but the tools required to manufacture the joint are very costly. For this reason a shear-plate-like connection with an estimated capacity of roughly 230kN was manufactured. Ring segments, cut from hydraulic tubing and welded to one face of a steel plate unite both components of a shear plate joint in one element, creating a strong and easy to assemble wood-to-steel connection, hereafter referred to as 'Ring Side Plates'. Ring Side Plates and couplings needed to connect to the test apparatus represent the 'lower support', whereas the INDUO-connector and its related couplings are referred to as 'upper support'. irvoduo Methods and Materials 33 The lower support consisted of the following: • A pairs of Ring Side Plates, mild steel of grade 300W • Two 7/8inch bolts (d=22.2mm), washers and nuts • Coupling block, mild steel of grade 300W • Two 1inch bolts (d=25.4mm), washers and nuts • Threaded coupling rod T/2 inch -12, (d=38.1mm) • Spacer plates: 2 x 5mm and 2 x 10mm thick with a pair of holes (d=26.4mm) Neither of the above mentioned materials were tested as these elements were over-designed and would thus be expected to remain linear elastic. Figure 42: Components of lower support Figure 43: Lower support assembled Figure 44: Ring Side Plate inoduo Methods and Materials 34 The upper support consisted of the following: • M20 steel rod, high-strength steel of grade 10.9 (EC3); washers and nuts • Steel plate, fixed to steel rod • Steel coupling, M20 and 11/2 inch -12 (d=38.1mm) inside-threads on opposite sides • DCDT measuring device to determine the displacement of the connection Figure 45: Upper support 3.2.3 Fabrication of test specimens Typically an INDUO-element is built-up by two timber halves and the end-grain embedded connectors. The procedure is as follows: inoduo Methods and Materials 35 1. Breakout (table saw, four-sided planer): • If necessary, lumber and wood products respectively are ripped, cut to length and planed to S4S-quality4 Final dimension for a) 120x120mm test specimens: 1530 x 134 x 60mm b) 100x100mm test specimens: 1530 x 134 x 50mm 2. Secondary processing (CNC-router): Inside face of timber halves: • Drill rows of holes Type A: Four parallel rows of 8 holes, d = 8mm, staggered holes matrix, depth: 19mm (outer row of holes) and 30mm (inner row of holes) Type B: Two parallel rows of 6 tapered holes, d = 7 to 9.5mm, depth: 40.4mm • Cut V-groove, depth: 20mm, length: 400mm Outside face of timber halves: • Mill three circular grooves, d = 101.6mm, width: 6mm, depth: 20mm, (for Ring Side Plates) • Drill two holes, d = 23mm, (for 7/8-inch bolts) 3a. Assembly of glued-laminated members (hydraulic press): • Apply adhesive on inside faces of timber halves • Sandwich connector between timber halves • Move composite member into veneer press and press for approximately 30 minutes until glue is cured. 3b. Assembly of screw-bonded members: • Sandwich connector between timber halves and clamp the setup to assure position • Pre-drill and countersink holes (d=4mm) to accommodate woodscrews (6x10) • Connect timber halves with a set of eight countersunk head woodscrews (for screw alignment see figure 47a) 4. Finish (shaper): • Taper end grain cross-section to desired 100x100mm and 120x120mm respectively (at the end where INDUO-connector is embedded) The Appendix under section 8.1.1 shows a detailed photographic documentation of all manufacturing steps. 4 Faces and edges are soundly planed to create a rectangular cross-section irroduo Methods and Materials 36 a) 50 2^ ^ 25 ^ 25 . 25 ?5 25 n ti n"n n i 25 25 25 25 +63 HttHH 25 25 25 458-3 -725 -O -T - 210 f 210 f- 160 -b) 4 ^ 25 50 25 25 T •|HHMI 25 25 25 25 25 25 25 25 +£.3-H-H+f++ 25 25 25 +- -470-3 -725--4—jl • 1530--i 210—-4—210 f— 160-•4--f Figure 46: Plan of timber halves: a) type A -100 combination; b) type A - 120 combination a) 4 £: •1530-80.0 40.4 40 4 -+ M T -* M 40.4 40.4 40.4 -668.0- -4 210.0 + 210.0 f- 160.0 -~0 5—5 5—C—B~~ o , Q fi Q S a_ 3 <^ CD 60.0 -4—f- 150.0 -f- 150,0 -f-4 458 JL_4--|HJ»-Figure 47: Plan of timber halves: a) type B-100 combination, screw-bond; b) type B - 120 combination inoduo Methods and Materials 37 3.2.4 Experimental setup Figure 48: Experimental setup: MTS 810 with control system and test member The experimental setup consists of 3 components: 1. Test apparatus All tension tests were conducted in the Timber Engineering laboratory on a servo-controlled hydraulic testing machine (MTS 810), with a maximum capacity of 250kN. The main parts of the machine are: • Solid and heavy machine body • Two cylindrical guide rails, featuring a cross-head, adjustable in vertical direction and to be locked at a desired height • Load cell to be suspended from the center of the cross-head, accommodating a pivoted coupling device to provide axial alignment of the specimen setup • Movable machine table, operated by a hydraulic power unit • Hydraulic system inoduo Methods and Materials 38 2. Control system The control system is built up by a servo-controller and a personal computer. The servo-controller regulates the hydraulic system by controlling the stroke of the machine table. An integral data acquisition system processes all the electronic data input of displacement and load measurements. Running LabTech Notebook pro software, version 10.1, the computer controls the data recording and converts the information received from the servo-controller unit into an ASCII file. Load, stroke and displacement of the INDUO-connection were sampled and recorded at 2 Hertz. A monotonic loading rate of 1.2mm/min forced the specimens to fail in five to seven minutes. 3. Test member Consisting of the specimen as well as the lower and upper support, the test member is the main component of the experimental setup. Figure 50 shows the standard setup of the upper support with a DCDT5 measuring the displacement of the INDUO-connection. Couplings and fasteners at both ends of the member complete the setup of the test member. Figure 49: Test member Figure 50: Upper support featuring a DCDT measuring device 5 DCDT: Direct Current Displacement Transducer irroduo Methods and Materials 39 3.2.5 Test procedure Since length and basic member setup were kept the same for all specimens, all the tests were conducted on one schedule, which can be described as follows: Mounting of test member • Connect specimen with threaded rod and upper coupling • Lift specimen onto machine table and screw coupling onto pivoted support of cross beam • Screw DCDT attachment to specimen • Install DCDT and adjust vertical position • Mount Ring Side Plates by means of two clamps, pressing fasteners into the grooves of the specimen • Fasten side plates with two 7/8inch bolts • Connect side plates with coupling block, using spacer plates to accomodate different member dimensions • Fasten lower coupling with two 1inch bolts Test • Start the test program • Watch the control panel and take notes of incidents occurring during test, such as cracking noises or general performance of specimen being loaded • In case of premature failure, stop data recording • In case of surviving the 180kN load limit, stop loading and data recording • Release residual load and disassemble test member in reverse order Documentation (after completion of test series) • Cut off 400mm long end grain piece from each specimen • Disassemble screwed or rip glued-laminated members along glue line to separate timber halves • Photograph damaged and deformed connection details • Document in detail all significant information The Appendix under section 8.1.2 provides detailed photographic information on the test procedure. irvoduo Results 40 4 Results Summarizing the experimental results of the research been conducted, the following sections present the analyzed data of test series 1 and 2. Each section will describe the behavior observed during load application and will present information on ultimate strength and displacement. In addition, section 4.2 will provide statistics on average ultimate strength and stiffness of test series 2 combinations (see section 8.2 for calculations). Picturing the failure area of each member, section 8.1.3 presents detailed photographic information of occurred failure modes. In varying combinations all four known failure mechanisms were observed (Figure 51). rVH n/S n/S 9 0 n/S row shear-out group tear-out bearing splitting Figure 51: Connection failure modes The moisture content and dry density of all tested specimens were determined according to ASTM D2395-93. The results are presented in the following table: Moisture Content [% LSL i (24 spec) DG Fir l22 PSL (22 spec ) LVL (22 spec.) X-LVL (9 spec.) mean 6.2 13.6 8.8 7.3 8.0 std dev 0.1 2.7 0.3 0.2 0.2 COV 1.6% 19.6% 3.7% 2.1% 2.6% Density [c |/cm3] LSL DG Fir PSL LVL X-LVL mean , 0.68 0.53 0.66 0.58 0.52 std dev 0.02 0.05 0.01 0.01 0.01 COV 3.6% 9.7% 1.8% 1.4% 2.3% Table 2: Moisture content and density of tested specimens incduo Results 41 4.1 Test series I The following member setups were tested under tensile loading: MA-100 MA-120 MB-100 MB-120 PA-100 PA-120 PB-100 PB-120 TA-100 TA-120 TB-100 TB-120 DA-100 DA-120 DB-100 DB-120 XA-100 XA-120 XB-100 XB-120 and S-TA-100, S-TB-100 Based on observations during the testing, it was decided to group the specimens according to general performance and failure mode. In doing so, TimberStrand®LSI_ and Douglas-Fir plywood, which exhibited superior and Douglas Fir and Microllam®LVL, with weaker properties, were configured in groups I and II, respectively. Due to inconsistent performance, Parallam®PSL was not assigned to either of the aforementioned groups and was separately analyzed. Table 3 gives an overview of analyzed data collected in test,series 1, showing the ultimate load, the load level where significant cracking noises were observed and in what manner the connection finally failed. Due to the test setup, the maximum load that could be applied was 180kN. For this reason test specimens that were not failed are indicated with a maximum load of >180kN. LSL Code Max Load [kN] cracking noises Failure conments TA1-100 124.1 >60kN ductile bearing and splitting perp. to strands TA2-100 112.7 > 50kN ductile bearing and splitting perp. to strands TA1-120 132.7 > 80kN ductile bearing and splitting perp. to strands TA2-120 130.9 > 70kN ductile bearing and splitting perp. to strands TB1-100 177.6 >120kN brittle failure of glueline TB2-100 > 180.0 >145kN no failure of glueline TB1-120 > 180.0 no no TB2-120 > 180.0 no no TB3-120 > 180.0 >160kN no Table 3: Analyzed data of test series 1 inoduo Results 42 X-LVL Code Max Load [kN] cracking noises failure comments XA1-100 104.2 > 45kN ductile bearing and splitting perp. to grain XA2-100 108.2 > 60kN ductile bearing and splitting perp. to grain XA1-120 127.2 > 50kN ductile bearing and splitting perp. to grain XA2-120 119.1 > 40kN ductile bearing and splitting perp. to grain XB1-100 174.2 >125kN brittle net section failure at last pair of pins XB2-100 163.8 >130kN brittle net section failure at last pair of pins -XB1-120 > 180.0 no no XB2-120 > 180.0 >140kN no XB3-120 > 180.0 no no DG Fir Code Max Load [kN] cracking noises failuro comments DA1-100 99.4 > 55kN rather ductile bearing and splitting DA2-100 82.0 > 50kN rather ductile bearing, splitting and group tear-out DA1-120 96.7 >70kN rather ductile bearing and splitting DA2-120 95.4 > 60kN rather ductile bearing and splitting DB1-100 165.2 > 90kN brittle violent failure, row shear-out along rows of holes DB2-100 165.8 >105kN brittle violent failure, splitting, deformed pins DB1-120 > 180.0 >140kN no close to failure, heavy crack, noises DB2-120 > 180.0 >120kN no close to failure, heavy crack, noises DB3-120 155.5 >90kN brittle splitting along rows of holes LVL Code Max Load [kNl cracking noises ! failure comments MA1-100 81.3 >45kN brittle bearing, splitting and group tear-out MA2-100 72.0 >35kN rather ductile bearing, splitting and group tear-out MA1-120 ' 76.0 >30kN rather ductile bearing and splitting MA2-120 81.9 > 50kN rather ductile bearing and splitting MB1-100 139.9 >70kN brittle splitting along rows of holes MB2-100 169.7 >100kN brittle splitting with group tear out, deformed pins MB1-120 145.0 >105kN brittle splitting along hole line, deformed pins MB2-12Q 167.6 >120kN brittle splitting along hole line, ripped-off pins MB3-120 163.9 > 110kN brittle splitting and group tear-out, deformed pins Table 3 (continued): Analyzed data of test series 1 inoduo Results 43 PSL Code Max Load [kN] cracking noises failure comments PA1-100 90.0 >40kN brittle bearing, splitting and group tear-out PA2-100 98.9 >50kN brittle bearing, splitting and group tear-out PA1-120 100.5 > 60kN rather ductile bearing, splitting and group tear-out PA2-120 87.0 >45kN rather ductile bearing, splitting and group tear-out PB1-100 143.6 >100kN brittle splitting, group tear-out, deformed pins PB2-100 166.1 >110kN brittle splitting, deformed pins PB1-120 171.3 >105kN rather ductile splitting along rows of holes, deformed off pins PB2-120 157.5 > 90kN brittle splitting along rows of holes, ripped-off pins PB3-120 151.0 >110kN rather ductile splitting along rows of holes, deformed off pins Table 3 (continued): Analyzed data of test series 1 4.1.1 Group I (TimberStrancfLSL & Douglas-Fir plywood) Figure 52: Group I: No failure for connector type B Figure 53: Group I: Severe bearing; a typical failure combinations mode for connector type A combinations In terms of strength and stiffness, combinations of connector type B and LSL or X-LVL outperformed all other specimens of the test series. None of the larger 120x120mm cross-sections could be failed at the maximum test load of 180kN. Damage to the fiber structure or deformation of the connector was not observed (Figure 52). While loading the test specimen, cracking noises indicating failure propagation, were rarely observed. Some of the smaller type B dimensions (100x100mm), however, failed. While both had a similar stiffness and high ultimate loads, LSL specimens typically failed due to a poorly inoduo Results 44 fabricated glue bond, whereas some X-LVL members experienced a sudden net section failure of the wood around the last pair of pins. In both cases failure was not governed by the connection itself. All connector type A combinations failed before reaching the 180kN test limit. After linear-elastic behavior up to an average of 95kN, the connection showed a comparatively ductile performance, before most of the specimens finally failed in a brittle manner caused by splitting perpendicular to the strands and the veneer layers, respectively. Investigating the failure area, the wood structure of the spike holes was significantly damaged due to excessive bearing (Figure 53). Displacements of more than 150% of the spike diameter were measured. The average ultimate load determined for LSL specimen was 125kN and 115kN for X-LVL. Interesting data was collected from the screw-laminated members S-TA1-100 and S-TB1-100. Compared to their glued-laminated counterparts, the screw-bonded specimens seemed to perform similarly or even better. Providing above average stiffness, S-TB-100 was not failed. The type A specimen presented the highest ultimate load of all TA combinations and remained on a high level before failing rapidly in splitting and shear (Figure 55). incduo Results 45 Figure 55: Load-displacement curves of TA-combinations incduo Results 46 Displacement [mm] Figure 56: Load-displacement curves of XB-combinations Figure 57: Load-displacement curves of XA-combinations irroduo Results 47 4.1.2 Group II (Douglas Fir & Microllam®LVL) Figure 58: Group II: Splitting along the rows of Figure 59: Group II: Bearing and relatively large holes; a typical failure mechanism of connector displacements due to shear failure of connector type B combinations type A combinations Two major trends were observed in this group: • Combinations with connector type A showed relatively ductile failure characteristics after reaching the maximum load with a comparatively low average ultimate load of 77kN for LVL and 93kN for Douglas Fir. • Unlike type A specimens, connector type B combinations provided higher stiffness and ultimate strength, but typically failed in a very brittle and abrupt manner, providing an average ultimate load of 157kN for LVL and 169kN for Douglas Fir. In general, severe splitting and shear failure along the rows of holes caused the sudden failure. In addition, Type A specimens sustained significant bearing and group tear-out. The pins of failed type B connectors were deformed and showed cracks at the pin base (Figure 131f, page 107). For type A connectors no evidence of damage to the connector was observed. Although two out of the ten type B specimens (DB1-120 and DB2-120) survived, severe cracking noises just before reaching the limit load and a delayed failure of DB2-120 15 seconds after the loading had stopped, indicated that 180kN is near the ultimate load. incduo Results 48 3 4 5 Displacement [mm] Figure 60: Load-displacement curves of DB-combinations 180 160 140 120 100 I 80 TJ BJ 3 60 40 20 0 3 4 5 Displacement [mm] ™^-DA1-100 -©-DA2-100 -H-DA1-120 -&-DA2-120 /if V Al/ ( )v r i i i i i i i Figure 61: Load-displacement curves of DA-combinations inoduo Results 49 180 , Displacement [mm] Figure 62: Load-displacement curves of MB-combinations 180 160 140 120 100 Displacement [mm] -O-MA1-100 -e— MA2-100 -S-MA1-120 -A-MA2-120 Figure 63: Load-displacement curves of MA-combinations incduo Results 50 4.1.3 Group III (Parallam® PSL) Figure 64: Group III: Bearing and tear-out of connector Figure 65: Group III: Connector type B type A combinations combinations with severe pin deformations or fracture As evident from the inconsistent performance for both type A and type B combinations, the connection's performance was governed by the local interaction of pins or spikes and the strand structure and was thus relatively random. The cavities between the strands seemed to act like pre-occurred damage to the wood structure. Therefore, an above average accumulation of these cavities in the area of a pin or spike hole led to premature crack propagation, resulting in splitting and a brittle failure mechanism. Investigating the connection region of type B members, it was found that specimens with a more interwoven strand layout performed in a more ductile manner, whereas members with strictly parallel alignment had failed in a brittle way. The advantageous interlocking of strands seemed to have less effect on type A connections. In general, type A specimens failed due to severe bearing followed by shear-off along the rows of holes. Approaching the ultimate load level, often entire strand segments were torn-out (Figure 64). With heavy deformations and partially ripped-off pins, connection type B's typical failure mechanism was splitting along the rows of holes, dependent on aforementioned parameters resulting in very brittle or more ductile behavior. The average ultimate loads determined for types A and B specimens were 94kN and 157kN, respectively. inoduo Results 51 180 Displacement [mm] Figure 66: Load-displacement curves of PB-combinations 3 4 5 Displacement [mm] Figure 67: Load-displacement curves of PA-combinations inoduo Results 52 4.2 Test series II As mentioned earlier, test series 2 consisted of a larger number of specimens with selected attributes. This provided a more representative statistical data base for those connection types that proved to be the most promising for practical applications. The following combinations were tested: S-MB-100 MB-100 S-PB-100 PB-100 S-TB-100 TB-100 S-DB-100 DB-100 Due to a more detailed data set developed for each setup, the specimens were no longer grouped according to observed behavior, but evaluated in their individual connector and material categories. LSL Code cmckmg noises |KN| failure comments (TB1-100) 177.6 >120kN brittle failure due to bad glueline (TB2-100) 180.0 >145kN no failure of glueline, no connection failure TB3-100 > 180.0 no no TB4-100 > 180.0 >170kN no TB5-100 > 180.0 no no TB6-100 > 180.0 >170kN no TB7-100 > 180.0 >160kN no TB8-100 > 180.0 no no TB9-100 > 180.0 no no TB10-100 > 180.0 >170kN no (S-TB1-100) > 180.0 no no S-TB2-100 > 180.0 no no S-TB3-100 > 180.0 no no S-TB4-100 > 180.0 >160kN no S-TB5-100 > 180.0 >170kN no Table 4: Analyzed data of test series 2 incduo Results 53 DG Fir Code Max Load [kN] cracking noises failure comments (DB1-100) 165.2 > 120kN brittle violent fail., row shear-out along rows of holes ( DB2-100 ) -165.8 > 110kN brittle violent failure, splitting, deformed pins DB3-100 177.6 >140kN brittle splitting, group tear-out DB4-100 > 180.0 >130kN no heavy cracking noises, close to failure DB5-100 143.5 >95kN brittle early cracking noises, splitting DB6-100 130.9 > 110kN brittle abrupt failure, splitting DB7-100 151.4 > 120kN brittle abrupt failure, splitting DB8-100 > 180.0 >150kN no heavy cracking noises DB9-100 > 180.0 no no DB10-100 > 180.0 >170kN no S-DB1-100 171.3 >125kN brittle abrupt fail., splitting, partial net section fail. S-DB2-100 173.3 >130kN brittle abrupt failure, splitting, ripped-off pin S-DB3-100 > 180.0 > 120kN no heavy crack, noises, close to failure S-DB4-100 > 180.0 no no S-DB5-100 170.5 > 90kN brittle violent failure, splitting PSL Code Max Load [kN] cracking noises failure ' comments ( PB1-100) 143.6 >100kN brittle splitting, group tear-out, deformed pins ( PB2-100) 166.1 >110kN brittle splitting, deformed pins PB3-100 141.7 >130kN brittle abrupt failure, splitting, PB4-100 135.9 >120kN brittle heavy cracking noises, violent failure, splitting, ripped-off pin PB5-100 157.7 >110kN brittle splitting, group tear-out PB6-100 152.9 >110kN brittle violent failure, splitting PB7-100 166.1 >150kN brittle splitting, strongly deform, pins PB8-100 171.5 >100kN brittle abrupt failure, splitting PB9-100 145.5 >130kN brittle abrupt failure, splitting, deform, pins, fissures at pin base PB10-100 151.9 > 110kN brittle violent failure, splitting S-PB1-100 160.5 > 90kN brittle splitting, group tear-out, deform, pins & fissures at pin base S-PB2-100 166.4 >120kN brittle abrupt failure, splitting S-PB3-100 156.8 >100kN brittle violent failure, splitting, row of pins ripped-off S-PB4-100 171.2 >130kN brittle violent failure, splitting, group tear-out S-PB5-100 > 180.0 >0kN no heavy crack, noises, close to failure Table 4 (continued): Analyzed data of test series 2 incduo Results 54 LVL Code Max Load [kN] cracking noises [ ! ! ! — ! ~ ! • — failure comments ( MB1-100 ) 139.9 >70kN brittle splitting along rows of holes ( MB2-100 ) 169.7 >100kN brittle splitting, group tear-out, deformed pins MB3-100 142.8 > 80kN brittle abrupt failure, splitting, deformed pins MB4-100 157.3 >140kN brittle abrupt failure, splitting, 3 ripped-off pins, fissures at pin base MB5-100 146.9 >120kN brittle abrupt failure, splitting, partial row shear-out MB6-100 147.6 >130kN brittle abrupt failure, splitting, deformed pins MB7-100 139.7 >105kN brittle splitting, deformed pins MB8-100 139.3 >100kN brittle "slower" failure, splitting, deform, pins MB9-100 147.6 >120kN brittle abrupt failure, splitting, ripped-off row of pins MB10-100 168.9 >120kN brittle violent failure, splitting, ripped-off row of pins S-MB1-100 157.1 >110kN brittle abrupt failure, splitting S-MB2-100 148.9 >100kN brittle splitting, 2 ripped-off pins S-MB3-100 168.9 >120kN brittle splitting, deformed pins S-MB4-100 175.6 >70kN brittle violent failure, splitting, group tear-out S-MB5-100 147.2 >80kN brittle splitting, group tear-out Table 4 (continued): Analyzed data of test series 2 4.2.1 Performance 4.2.1.1 TimberStrantfLSL r « * Figure 68: LSL: No damage observed at the pin holes Figure 69: LSL: No deformations of the connector Similar to the observations made in test series 1, in terms of ultimate strength, LSL outperformed all other materials. None of the 13 specimens were failed. At the limit load of 180kN the testing was stopped and the members were unloaded. For 6 specimens however, cracking noises were noticed around 160 to 170kN, indicating the beginning of inoduo Results 55 failure development. For the rest of the sample set no cracking noises or signs of distress were observed. Examining the connection area of the test members after cutting them open, it was found that neither the wood structure nor the connectors were damaged or deformed. 3 4 5 Displacement [mm] Figure 70; Load-displacement curves of TB-combinations 180 3 4 5 Displacement [mm] -0-S-TB1-1OO -O-S-TB2-100 -B-S-TB3-100 A S-TB4-100 -*~S-TB5-100 Figure 71: Load-displacement curves of S-TB-combinations inoduo Results 56 As listed in figures 70 and 71, it was evident that the alternative screw-bond of the timber halves did not have an apparent influence on the stiffness performance of the connection. Further evaluation of the test data (Sections 4.2.2 and 8.2) confirmed this. 4.2.1.2 Douglas Fir Figure 72: DG fir: Splitting along Figure 73: DG fir: Shear failure in the plane of the pins rows of holes Even though six of the 13 test specimens survived the 180kN load limit, for almost all Douglas Fir members heavy cracking noises were observed. Failure typically occurred very abruptly. Splitting along the rows of holes and shear-off along the plane of the pins caused extremely violent and brittle failures. Comparing and analyzing screw-bonded and glued-laminated specimens, it was found that the alternative screw-lamination did not have a significant impact on the failure itself. Without exception, both types of lamination presented very similar failure mechanisms with failure in the plane of the pins. Investigating the failure areas of the screw-bonded specimens, no evidence was found that the screws influenced or contributed to the overall tensile strength and performance of the connection. incduo Results 57 Displacement [mm] Figure 75; Load-displacement curves of S-DB-combinations inoduo Results 58 Figure 76: PSL: Splitting along the Figure 77: PSL: Deformation of the connector pins rows of holes Except for one specimen, member combinations with PSL failed due to splitting along the rows of holes before reaching the 180kN test limit. While loading the member, cracking noises indicated failure propagation, leading to a sudden but less violent failure. For most of the connectors strong deformations and fissures at the base of the pins were found; some pins were ripped-off. Similar to Douglas Fir specimens, glued-laminated and screw-bonded members performed similarly. incduo Results 59 --0-S-PB1-1OO -e-S-PB2-100 -B-S-PB3-100 A S-PB4-100 •->r~S-PB5-100 01 2345678 Displacement [mm] Figure 79; Load-displacement curves of S-PB-combinations irvoduo Results 60 4.2.7.4 MicrollarrfLVL Figure 80: LVL: Splitting along rows of holes Figure 81: LVL: Ripped-off pins Before reaching the limit load, all LVL specimens mostly failed due to splitting along the rows of holes. Similar to the observations made for Douglas Fir, the LVL combinations failed in an extremely violent and brittle manner. Typically, the connector pins were strongly deformed and partly ripped-off. Glued-laminated and screw-bonded members showed similar behavior. Figure 82: Load-displacement curves of MB-combinations inoduo Results 61 Figure 83: Load-displacement curves of S-MB-combinations inoduo Results 62 4.2.2 Strength and Stiffness Since glued-laminated and screw-bonded test specimens performed similarly under tensile loading, it was decided to merge both sets of samples. Therefore by providing a larger sample size of 15 specimens, statistically more significant values for the characteristic strength and stiffness could be calculated. Tables 5 and 6 display information on average ultimate strength and displacement for connector type B combinations. For specimens that were not failed, it was assumed that their ultimate load equated 180kN. Ultimate Load [kN] LSL DG Fir PSL LVL min value > 180.00 130.88 135.91 139.30 max value > 180.00 > 180.00 > 180.00 175.62 mean > 180.00 168.63 157.85 153.16 std dev 15.27 12.62 12.30 COV 9.1% 8.0% 8.0% Table 5: Statistics on ultimate load Displacement at ultimate load [mm] LSL DG Fir PSL LVL min value 0.91 1.12 0.6 0.72 max value 2.77 2.45 2.41 2.4 mean 1.57 1.71 1.43 1.49 std dev 0.50 0.43 0.56 0.57 COV 32.0% 25.1% 39.2% 38.3% Table 6: Statistics on displacement at ultimate load To determine the stiffness S of a connection, typically equation 4.1 is chosen to calculate the specific stiffness properties. S= 10 h) (4.1) ^40 -''lO where: incduo Results 63 S = Stiffness of the joint [N/mm] F40 = Strength property at 40% of the ultimate load [N] F10 = Strength property at 10% of the ultimate load [N] d40 = Displacement at 40% of the ultimate load [mm] d40 = Displacement at 10% of the ultimate load [mm] Due to inconsistent stiffness performance at the beginning of the loading process, it was found that the 10%-40% approach does not precisely represent the actual stiffness of the connection. To provide more accurate values, stiffness was determined by using the 30%- and 70%-ultimate load points. 180 Figure 84: Different approaches to determine the connection stiffness Figure 84 shows typical load-displacement curves of the test series, presenting a "softer" (DB5-100) as well as a "stiffer" behavior (PB8-100) at the beginning of the loading process. Comparing the dashed and solid straight lines indicating different stiffness, it is evident, that the 30/70-approach creates more realistic results than the 10/40-method. incduo Results 64 For this reason the stiffness of the connection is determined as follows: S = tll) " ^30 (4.2) where: S = Stiffness of the joint [N/mm] F7)> = Strength property at 70% of the ultimate load [N] F30 = Strength property at 30% of the ultimate load [N] d70 = Displacement at 70% of the ultimate load [mm] d30 = Displacement at 30% of the ultimate load [mm] Statistics on stiffness values calculated using both approaches are presented in table 7, showing that the 30/70 method generally results in a significantly lower variability of values and, except for Douglas Fir, a smaller average stiffness. Stiffness [N /mm] S-TB/TB S-DB / DB 10/40 30/70 10/40 30/70 min value 79,412 91,139 43,626 86,747 max value 360,000 "200,000 300,000 318,797' mean 166,686 135.223 119,752 170.557 std dev 82,695 35,740 68,109 70,471 COV 49.6% 26.4% 56.9% 41.3% S-PB / PB S-MB/MB 10/40 30/70 10/40 30/70 min value 53,581 96,454 39,678 62,105 max value 2,293,556 265,9:19 439,058 281,529 mean 351,768 •«> 154,228 186,075 ' ' 140,235 std dev 592,150 52,960 145,808 v 61,473 COV 168.3% 34.3% 78.4% 43.8% Table 7: Statistics on different 10/40- and 30/70-connection stiffness inoduo Results 65 Average ultimate strength and stiffness are elementary mechanical properties used to develop a basic understanding of the fasteners behavior. To model the characteristic connection strength, however, typically the lower 5th percentiles of the ultimate strengths have to be determined. Looking for the most accurate distribution to generate the 5th percentile values, a subroutine of the RELAN6 software was used to fit Normal, Lognormal, 2P- and 3P-Weibull distributions to the ultimate strength data. The software calculated an overall data fitting error for each data set and developed a distribution function that fits a curve to all data points. Applying these fitted functions, the following formulas were used to calculate the 5th percentile values of the respective distributions: Normal Distribution: Xp =/J,-k(T (4.3) where: xP = Strength property at the 5th percentile [N] u = Mean value [N] k = Factor related to percentile P, level of confidence and sample size (k = 1.645) a = Standard deviation [N] Lognormal Distribution: A",, =/• <T''J/'1 (4-4) where: xP = Strength property at the 5th percentile [N] Pm = Log mean value ain = Log standard deviation zp = Standard normal number (z score) for a given percentile (zPi005 = 1.645) and (4.5) //ln =ln//-0.5-aln: (4.6) 6 RELAN: RELiabilty AA/alysis software developed in the Department of Civil Engineering at UBC incduo Results 66 where: Pin = Log mean value ain = Log standard deviation u = Mean value [N] a = Standard deviation [N] Weibull Distribution: jt, = A-0 + wi{-ln(l-/>)]*"' <4-7> where: Xp = Strength property at the 5th percentile [N] x0 = Location parameter (x0 = 0 for a 2P-Weibull distribution) m = Scale parameter k = Shape parameter P = Percentile value Analyzing the data generated by RELAN, it was found that 3P-Weibull functions provided the best fit on the lower tail of the ultimate strength data set. Table 15 in section 8.2 presents detailed information on the different fitting errors and distribution functions computed by RELAN. With these fitted functions, the following 5th percentiles were calculated: 5th percentile strength [kN] Normal Lognorm. 2P-Weib. 3P-Weib. LSL (180.00) DG Fir 141.98 144.75 138.24 138.24 PSL 135.75 137.98 132.98 135.64 LVL 133.19 133.81 131.07 137.48 Table 8: 5th percentile strengths of respective distributions inoduo Results 67 Accounting for the short term duration of loading (test specimens were typically failed in 5 to 7 minutes), the 5th percentile results were multiplied with a factor KDOi to generate the characteristic values of maximum tensile capacity (Table 9). where: xP = Strength property at the 5TH percentile [N] KDOL = Factor to account for short term loading (KDOL= 0.8) Tk = Characteristic value for the maximum tensile capacity [N] Characteristic values of maximum tensile capacity [kN] Normal Lognorm. 2P-Weib. 3P-Weib. LSL (144.00) DG Fir 113.58 115.80 110.59 410.59 PSL 108.60 110.39 106.38 108.51 LVL 106.55 107.05 104.85 * : 109.98 Table 9: Characteristic values of maximum tensile capacity The RELAN data fitting subroutine was also used to compute the 5th percentile values of the connection stiffness. Similar to the results of the 5th percentile of the connection strength, 3P-Weibull distributions provided the most accurate data fit. The following tables present the complete set of results for all distributions and the 10/40- as well as the 30/70-method to determine the individual connection stiffness. 10/40 Normal Lognorm. 2P-Weib. 3P-Weib. LSL 54,615 62,809 51,169 74,200 DG Fir 35,270 41,227 34,229 45,758 PSL 41,946 41,710 37,687 73.608 LVL 25,140 30,231 18,292 38,402 Table 10: 5 percentile of 10/40-stiffness 5th percentile stiffness [N/mm] J30770 Nolmal. Lognorm. 2P-Weib. ;3P-Weib. LSL 77,658 82,623 74,769 „85,913 DG Fir 71,800 78,982 68,820 88,012 PSL 84,626 86,900 80,860 101,784 LVL 52,888 60,378 52,027 63,571 Table 11: 5 percentile of 30/70-stiffness incduo Discussion 68 5. Discussion 5.1 Evaluation of test results Appraising the findings of both tests series, with respect to member material and connector type, two major conclusions were reached: 1. Material: Superior tensile strength and failure-free performance of type-B test members significantly distinguishes LSL from LVL, PSL and Douglas-Fir lumber. Assuming the 180kN upper bound limit as the capacity of the unfailed specimens, the latter three generally had 30% weaker characteristic strength properties accompanied by brittle failure modes under tensile loading of the joint. In combination with connector type A, LSL furthermore showed an advantageously ductile failure behavior, providing the highest average ultimate load value of all type A member setups. Conclusion: LSL outperforms LVL, PSL and Douglas-Fir lumber. 2. Connector: Connector type B combinations presented high characteristic tensile strength values and failed typically in splitting along the rows of holes with bending, and in some cases rupture of the pins, whereas type A member setups were primarily engaged in bearing and group tear-out of the wood, eventually failing in tension perpendicular to the strands or the veneer layers; Douglas Fir members typically failed in splitting of the wood. In addition, type A combinations presented a 60% lower average ultimate tensile strength. Conclusion: Connector type B is stronger than type A, but causes abrupt and very brittle failures at high ultimate load levels. Figure 85 shows all possible material/connector setups, indicating combinations with weak (white), stronger (light grey) and most beneficial (dark grey) tensile strength properties. Due to the promising performance of LSL-type A combinations in test series 1, this connection setup is specially indicated (light grey dot). inoduo Discussion 69 LSL LVL PSL DG Fir Type A Type B Figure 85: Classification of member setups according to tensile performance The axial resistance of a dowel-type connection with multiple fasteners is primarily dependent on the dimension, the strength, the number, the spacing and the edge distances of the fasteners, as well as the mechanical properties and characteristics of the member material. In the case of the INDUO-connector, except for the loaded edge distance (set to 10d), all fastener related parameters are defined by the connector itself, leaving only the cross-section and the material of the member as variable factors. Thus, the tensile strength of the connection is directly dependent on the quality and strength of the member material. Every wood or wood-based material features man-made and / or natural characteristics that influence the material and connection strength. When the applied load exceeds the capacity of the wood joint, failure typically initiates at the weakest spot of the connection. Solid wood with its non-homogeneous structure contains various weakening characteristics and 'natural defects' such as knots, checks and varying density (growth-rings, late-early wood) that present such weak points. To create a more uniform and less heterogeneous wood-based material, engineered wood products were developed, eliminating major wood defects and evenly distributing minor weakening characteristics over the entire volume of the member. In the manufacturing process, however, where the original fiber structure is partially destroyed, the recreated wood product shows man-made defects that likewise present undesired characteristics. A close look at the end grain of PSL (Figure 86a) reveals relatively large voids embedded in the strand structure (white circles). In addition, PSL strands and LVL plies feature little surface cracks (white box) that derive from the peeling and drying process during the veneer manufacture as incduo Discussion 70 well as from bending while forming and pressing the strand mat into a billet (PSL manufacture). Figure 86: Close-up of end grain: a) PSL; b) LVL; c) Douglas Fir; d) LSL LSL's advantageous connection strength properties originate from the high density (0.68g/cm3 7) and uniformity of the material and its interwoven strand structure. In comparison to PSL, the end grain of LSL does not show any visible cavities (Figure 86d) or initial damage to strands, because the thin and flexible LSL strands overlap and bend without creating hollow spaces and surface cracks, thus reducing potential weak spots in the composite structure. Providing a more cross-layered strand orientation than PSL, the interwoven fiber structure of LSL seems to act like inner reinforcement of the mainly parallel aligned composite. This material property is considered to be responsible for the fact that, in 7 Density value provided by manufacturer TrusJoist irroduo Discussion 71 contrast to Douglas Fir, LVL and PSL, none of the LSL specimens failed in wood splitting along the rows of holes. In conclusion, LSL's performance is based on high material density and uniformity, accounting for a high embedding strength and the unique strand structure that reduces splitting of the material. 5.2 Comparison of characteristic strength values For the most common fasteners used in contemporary wood construction, timber codes provide the necessary information to calculate and dimension all structural components related to the joint. For connection techniques that have not been introduced into the code, reliable design information has to be supplied by the manufacturer of the fastener. This data is typically generated in specific test series. 5.2.1 Connection Model Due to the costly procedure for an official approval and certification of the INDUO-connector type A, in 2000 it was decided to modify the fastener shape so that it can be modeled and calculated as a "tight-fitting dowel connection with inside steel plate" according to DIN1052-1988 (BlafB 2001). Connector body ( = inside steel plate) Pin (= tight-fitting dowel) Wood (= side member) Figure 87: Connection model With this connection model, the specific design strength for the tensile capacity of the INDUO-connector can be calculated according to any timber code, provided that the respective code includes dowel-type fasteners. The characteristic tensile strengths inoduo Discussion 72 derived from the results of test series 2 can then be compared and verified with corresponding values generated from code design strengths. Using the aforementioned connection model, in section 5.2.2 these design strength values will be determined according to the new German DIN1052-2000 (Draft), the European EC5, the Canadian CSA 086.1 and the US-American ASCE 16-95 timber code. All four codes are based on a Limit States Design philosophy, but vary in detail due to different safety approaches. With a step-by-step approximation of the different code results, the characteristic tensile strength for each design approach will be generated and compared with the data developed from the test series. 5.2.2 Determination of code design values To create a uniform and comparable set of results, values for member dimensions, material properties, service conditions and duration of loading are defined as follows: Connection Model: Dowel-type connection with inside steel plate and wooden side members. Number of dowel-type fasteners: 12 Number of shear planes per fastener: 2 Components of connection: Side members: Wood or wood product: Douglas Fir, No1. & better grade LSL, 1.5E grade LVL, 1.9E grade PSL, 2.0E grade Moisture content: MC < 19% Cross-sectional area: 33 x 100mm Main member: Inside steel plate, spherical cast iron of EN-GIS-500-7 grade defined in EN1563 Characteristic ultimate tensile strength: fuk = 500 N/mm2 Characteristic yield strength: fyk = 320 N/mm2 Cross-sectional area: 14 x 100mm incduo Discussion 73 Fastener: Tight-fitting dowel8 / bolt9, spherical cast iron of EN-GIS-500-7 grade, defined in EN1563 Dimension of fastener: d = 8mm, I = 80mm Service condition and duration of loading: Duration of loading: Medium or standard term loading (1 week - 6 months) Service conditions: Temperature: 20° centigrade Relative humidity of the surrounding air: 65%, exceeding 85% only for a few weeks of the year Connection is not exposed to any corrosives Treatment: The wooden side members are not impregnated with any strength reducing chemicals Spacing and distances of fasteners: Parallel to grain direction: a-i = 40.4mm • 5.05d Perpendicular to grain direction: a2 = 25.0mm • 3.13d Loaded edge: a3 = 80.0mm • 10.0d Unloaded edge: a4 = 37.5mm • 4.67d „13 r- -j CO ro (0 ^ CO o o o o o 33 0 — 33.* 30 0 - 40 4 30 0 • Ll a3 = 10d 40 4 1-D a, = 5.05d • 40 4 • 10 0 10 0 Figure 88: Plan of connection according to DIN1052-2000 and EC5 according to CSA 086.1 and ASCE 16-95 inoduo Discussion 74 Failure modes according to the European Yield Model: EC5, CSA 086.1 and ASCE 16-95 use the European Yield Model (EYM) to describe typical failure modes occurring in dowel-type connections. Based on these failure models the codes provide equations to generate the nominal lateral strength resistances per shear plane and fastener. The failure modes are defined as follows: Failure mode I: Bearing-dominated yield of the wood fibers in contact with the fastener Failure mode II: Fastener yield in bending at one plastic hinge point per shear plane and bearing-dominated yield of the wood fibers in contact with fastener Failure mode III: Bearing-dominated yield of the main member in contact with the fastener (Not compatible with actual performance of INDUO-connector) Failure mode IV: Fastener yield in bending at two plastic hinge points per shear plane with limited localized crushing of wood fibers near the shear planes (Not compatible with actual performance of INDUO-connector) Figure 89: Failure modes according to European Yield Model Since the failure modes III and IV do not represent the characteristic performance of the INDUO-connector and in addition neither of these failure types was observed in the test series, only mode I and II will be considered in the design calculations. Each of the following sections (5.2.2.1 to 5.2.2.5) presents for the design procedure and the equations used to calculate the axial strength for dowel-type connections according to the respective timber code. 0| Ol Ol o I oi IO o o inoduo Discussion 75 5.2.2.1 Dim052-2000 (Draft) R, = R. (5.1) w, ,•/!,•//. (5.2) <-R=j2-fi M^-I),.c' (5.3) provided that (5.4) nun M1 o n \U)d M , =0.26- /" . d: (5.5) (5.6) A, =0.082 (I-0.01 d) /v£, (5.7) (5.8) where: Fd Rd Rk kmod Ym nef n nr nr ns d My,k fh,k Veq Ii fu,k Pk = Design force [N] = Design value of the load-carrying capacity of the connection [N] = Characteristic load-carrying capacity per shear plane and fastener [N] = Factor accounting for the effect of load duration and moisture content (kmod =0.8) = Partial factor for steel in timber connections (Ym = 1.1) = Effective number of fasteners in a row = Number of fasteners in a row = Effective number of fasteners in a row = Number of rows = Number of shear planes = Fastener spacing in grain direction [mm] = Fastener diameter [mm] = Characteristic fastener yield moment [Nmm] = Characteristic embedding strength of the wood [N/mm2] = Required minimum thickness of the wood side member (treqs I, = 33mm) = Embedding length of fastener in the wood side member [mm] = Characteristic ultimate tensile strength of the fastener [N/mm2] = Characteristic density of the wood [kg/m3] = Reduction factor accounting for a, < a^ req = 7d incduo Discussion 76 5.2.2.2 EC5 (Eurocode 5) Fd<Rd . C.9) Rj =R,i (5.10) t The lesser Rd0 of mode 1 and 2: M ON / A k = ^-082 • (1-0.0 \-d)- /?, • Arrt (5.13) (5.14) (5.15) Failure mode I: n _ mod K/n -:— i.- -A. W (5.11) Failure mode II: where: Fd Rd Rd,0 n nr ns kmod Ym,w Ym f h,k ll d My,k fu,k Pk ka 4. -2 + -OH k. mod (5.12) = Design force [N] = Design value of the load-carrying capacity of the connection [N] = Design value of the load-carrying capacity per shear plane and fastener [N] = Number of fasteners in a row = Number of rows = Number of shear planes = Factor accounting for the effect of load duration and moisture content (kmod =0.8) = Partial factor for wood and wood composites (Vm,w =1.3) = Partial factor for steel in timber connections (Ym = 1.1) = Characteristic embedding strength of the wood [N/mm2] = Embedding length of fastener in wood side member [mm] = Fastener diameter [mm] = Characteristic fastener yield moment [Nmm] = Characteristic tensile strength of the fastener [N/mm2] = Characteristic density of the wood [kg/m3] = Reduction factor accounting for < a1p req = 7d < inoduo Discussion 77 5.2.2.3 CSA 086.1 F(l<P, (5.15) Pt = c|>. PH-nt-n, n, • J, (5.16) t The lesser pu of mode 1 and 2: Failure mode I: P.t =o.s-/, • </•/, (5.17) Failure mode II: p.t =0.8- /,•</= (5.18) Jr =0.33 — /, ) ( S ^ rf J U/ J <-0.3>! (5.19) where: Pr = Factored lateral strength of a bolted connection [N] <t> = Resistance factor (cp - 0.7) Pu = PU(KD- KSF- KJ) pu = Lateral strength resistance for loading in grain direction [N] KT = Fire-retardant treatment factor (KT = 1.0) KSF = Service condition factor (KSF = 1.0) KD = Load duration factor (KT = 1.0) ns = Number of shear planes nr = Number of fastener rows nF = Number of fasteners in a row JF . = JQ-JL'JR JL JR JG d s fi G f2 = Factor for loaded end distance (JL= 1-0) = Factor for number of rows (JL = 0.8) = Factor for two to maximum 12 fasteners in a row = Embedding length of fastener in the wood side member [mm] = Fastener diameter [mm] = Fastener spacing in the row [mm] = Embedding strength of the wood [N/mm2] (f, =63-G-(1-0.01d)) = Mean oven-dry density = Embedding strength of the inside steel member [N/mm2] (set to f2 = 10,000 N/mm2 ~ infinite embedding strength) = Yield strength of the steel fastener [N/mm2] incduo Discussion 78 5.2.2.4 ASCE 16-95 7. <<l>, A Z' / (5.20) Z'=Z n, C. C\, C, C\ (5.21) t * The lesser Z of mode 1 and 2: C. = m t Failure mode I: Z = 1.06 </•/ / Failure mode II: (5.22) /// = u- \Ju' - I it = ! + /•- - + -2 l£m-A„ £5-Aj Z = 2M cl /,/,„. -^-^ (5.23) 2-(l + K.) 2-/4,-(2 + /?.)J2 A.' •< — . h 3 • /" • / j em s-(5.24) (5.25) (5.26) (5.27) where: <t>z A Zu Z' z nF nr n Cg CM CT CA REA ES EM As Am Resistance factor connections (<PZ = 0.65) Time-effect factor (A = 0.80) Connection force due to factored loads [lbs] Adjusted connection lateral resistance [lbs] Reference connection lateral resistance [lbs] Total number of fasteners in the connection Number of fastener rows Number of fasteners in a row Group action factor Wet service factor (CM = 1.0) Temperature factor (CT = 1.0) Geometry factor (Cfi = 1.0) = the lesser of £,-4 E_-A or E.A.. Modulus of elasticity of wood side member [psi] Modulus of elasticity of steel main member [psi] Gross cross-sectional area of main member [in2] Sum of gross cross-sectional areas of side members [in2] inoduo Discussion 79 Y = 270,000 dx 5 [lbs/in] d = Fastener diameter [in] s = Fastener spacing in grain direction [in] ls = Embedding length of fastener in side member [in] fes = Embedding strength of wood side member10 [psi] fem = Embedding strength of main member [psi] (set to 10,000 N/mm2 = 1.45-106 psi = infinite embedding strength) Re ~ fem / fes fyb = Dowel bending yield strength [psi]; (fyb = 60,000 psi) 5.2.3. Characteristic strength values To determine how realistic the connection model defined in section 5.2.1 describes the actual tensile capacity of the INDUO-connector, characteristic connection strengths derived from design values calculated according to sections 5.2.2.1-4 are compared with the characteristic values generated from test results. The basic design equation for mechanical connections based on a Limit States Design approach is as follows: Dc < Rc (5.28) « Rc = O • rc (5-29) where: Dc = Design force applied to connection or 'Demand' Rc = Factored strength of a mechanical connection or 'Resistance' rc = Reference strength of a mechanical connection 0 = Resistance or modification factor Equation 5.29 can be further modified by factoring out the group action factor that accounts for the effects of more than one fastener in a mechanical connection (Equation 5.30). 10 Table 8A, LRFD Structural Connections Supplement of the Manual for Engineered Wood Construction, AF&PA / American Wood Council inoduo Discussion 80 R(. (5.30) (5.31) where Factored strength of a mechanical connection or 'Resistance' Specific characteristic strength value of a mechanical connection Group action factor Resistance or modification factor Applying equation 5.30, Table 12 presents the stepwise approximation of the specific characteristic tensile strength value. Column IV, 'Adjustment of embedding strength', considers the relatively small wood embedding strength value provided in the Canadian code by adjusting it to the correspondent values of the other timber codes. Based on two different test procedures (Figure 90), the embedding strength of wood and wood-based products is determined according to the American ASTM D5764a-1997 and the European EN 383-1993 test standards, respectively. In the timber design codes, however, the embedding strength values are calculated using the fastener diameter and the mean oven-dry density as variables and specific calibration factors that vary for each code. Although the US and Canadian embedment values are based on the same testing procedure, the Canadian embedment design values are significantly more conservative. To eliminate this discrepancy in the comparison with test results an adjustment factor has been applied in table 12, column IV. Figure 90: Different test procedures to determine the embedding strength of wood and wood-based material; a), DIN EN 383-1993 b) ASTM D5764a-1997 inoduo Discussion 81 Similarly, the group reduction factor in the Canadian code is much more severe than in the other design codes. To allow for a more realistic comparison of the characteristic values the design strengths were modified in column II by eliminating the group action factors. Cells featuring an 'arrow' indicate that due to code specifications the respective calibration step is not applicable. LSL, 1 5E Ratio l/V Design strength (factored resistance) No group reduction factor (1/kr) No resistance / modification factor (1/0) Adjustment of embedding strength Specific char, tensi-c strength value [N] l/V I II III IV V DIN 1052-2000 64% 80,108 113,682 125,050 • 125,050 EC5 81% 98,755 • 122,193 • 122,193 CSA 086.1 25% 26,076 60,215 86,022 105,373 105,373 ASCE 16-95 60% 76,108 82,299 126,613 • 126,613 Table 12: Example showing a step-by-step approach to determine characteristic values for tensile capacity Due to different safety approaches of each timber code, the results for the design strength of the dowel-type connection model defined in section 5.2.1 vary significantly from each other. Especially, the Canadian timber code with a factored resistance of 26.1kN represents a very conservative design approach. Comparison of characteristic strength values 1 [kN] LSL Ratio i/l DG Fir Ratio i/l PSL Ratio i/l LVL Ratio i/l 1 Char, strength Test series 2 144.00 110.59 108.51 109.98 II DIN 1052-2000 125.05 87% 114.94 104% 116.11 107% 116.11 106% III EC5 122.19 85% 108.51 98% 110.04 101% 110.04 100% IV CSA 086.1 105.37 73% 91.94 83% 94.79 87% 94.79 86% V ASCE 16-95 126.61 88% 111.40 101% 112.92 104*i SlJlillPsSl 112.92 103% Table 13: Comparison of characteristic connection strength values incduo Discussion 82 Comparing the characteristic strength values, Table 13 shows that overall the connection model used to determine the code design strengths reasonably represents the actual tensile strength properties of the INDUO-type B connector. Except for LSL, that features significantly lower code values, the characteristic strengths calculated for Douglas Fir, LVL and PSL show relatively small deviations from the values generated from the test series. The Canadian code generally provides the most conservative results, whereas DIN1052-2000 and ASCE 16-95 predict a slightly higher characteristic strength value (dark grey cells). The European, Canadian and American timber codes assume that for dowel-type connections with multiple fastener configurations, providing sufficient spacing and loaded end distance of the fasteners, connection strength values according to the European Yield Model can be achieved. The characteristic performance of the INDUO-connection with predominantly brittle failure behavior therefore does not strictly comply with the failure modes defined by the EYM. For this reason, it is pointed out that the tight-fitting dowel model does not comprehensively describe the actual performance of the INDUO-fastener. Although it is implied that, for dowel type connections, the values given by the EYM provide reasonable estimate of load capacity, brittle failure modes are not explicitly considered. They are deemed to be avoided by the prescription of dowel spacing and end distance. From testing experience, however, it is evident that brittle failure modes often dictate the load capacity and it is thus recommended that appropriate design equations for brittle failure modes to be developed. incduo Discussion 83 5.3 Evaluation of connection stiffness with structural model Figures 91-93 show the Thalkirchen Bridge over the River Isar in Munich, Germany, built-up by a wooden space truss system, featuring Glulam beam elements with special steel connectors at both ends and spherical cast steel nodes with inside thread. The wood-to-steel joint of the beam is a tight-fitting dowel connection with inside steel plate. All elements were prefabricated in the shop and assembled on-site, simply connecting the beams and nodes with threaded bolts. Completed in 1991, it is still the only wooden highway bridge using a space truss system to support the road deck. Figure 91: Thalkirchen Bridge, Munich, Germany Figure 92: Support with node and Figure 93: Node in the truss system connected beams inoduo Discussion 84 Being well suited for transferring high tensile loads, the INDUO-fastener can be applied in heavy-timber structures like the space truss system of the Thalkirchen Bridge. Compared to the dowel-joint that is exposed to the weather and an corrosive environment resulting from the use of road salt during winter time, the relatively small and compact INDUO-connector is sand wiched and protected in the wood member, providing a high tensile load capacity. Figure 94 shows how the INDUO-connector could be applied as a substitute for the tight-fitting dowel connection used in the structure of the bridge. Table 14 presents a stiffness calculation of the proposed connection setup that shows the relatively small deformations under a tensile design load of 60kN. inoduo Discussion 85 Example: INDUO-connector applied in 3D-Truss beam # Component Grade I (mm) (mm ) MOE (N/mm2) Stiffness (N/mm) Displacement (mm) 1.1 Wood member 120x120 (Beam half): DG Fir, SS 1,000.0 14,400 12,000 172,800 0.347 1.2 Wood member 100x100 (Beam half): DG Fir, SS 1,000.0 10,000 12,000 120,000 0.500 2 INDUO-connector: 247.0 100,140 0.599 3 Bolt M20: 10.9 70.8 245 210,000 726,695 0.083 4 Bolt + Connector 317.8 88,012 —^ 5 Total 100x100: 50,773 1.182 6 Total 120x120: 58,312 1.029 Table 14: Calculation example on stiffness and displacement of INDUO-connector in 3D-truss beam *) Values from test series of research project inoduo Conclusion and Recommendations 86 6 Conclusion and Recommendations Conclusion This research project produced comprehensive results on tensile strength, stiffness and failure performance of the INDUO-Heavy-Timber joint. Overall 99 specimens featuring member setups of different material-connector combinations were tested and evaluated. Furthermore, the results for the characteristic tensile strength were compared with values derived from international timber codes. In conclusion, it can be said that the INDUO-connector type B, providing significantly higher tensile strength properties, outperforms the older type A version. In combination with TimberStrand®LSL connector type B presented the best test results in terms of tensile strength and failure performance. For Microllam®LVL, Parallam®PSL and Douglas-Fir lumber both connector types generally showed brittle failure mechanisms. Investigating an alternative lamination method to connect the timber halves of the INDUO-members, it was found that screw-bonded and glued-laminated test specimens did not present different tensile strengths and failure modes. The comparison of the characteristic tensile strength with numbers derived from design values of different international timber codes (Europe, Germany, Canada and USA) showed that the INDUO-connector type B can be modeled and calculated as "doweled or bolted connection with inside steel plate". While all four codes generally complied with the characteristic tensile strength properties generated from the test results, due to different safety approaches, the respective design values differed significantly from each other. Here, the Canadian code proved to be the most conservative and the European code the most progressive design approach. Recommendations After more than two years of research and comprehensive investigations, it can be said that the INDUO-connection meets most of the state-of-the-art performance requirements stated by Madsen (page 11). Presenting high strength and high stiffness properties, the INDUO-heavy-timber system is both easy to manufacture and erect and meets esthetic as well as fire protection demands due to the embedment of the connector in the timber member. In comparison with other mechanical fasteners, such as nails, bolts or steel incduo Conclusion and Recommendations 87 dowels, however, the undesirably brittle failure mechanisms of the INDUO-connection under tensile loading present a major disadvantage. Similar to the proposed use of glued-in rods with welded steel plates (page 12), it is therefore recommended to design the INDUO-connection in a way that failure will occur in the ductile steel bolt which joints the embedded connector and the adjacent structure. Due to budgetary limits, this research project could only focus on one specific field of interest: The tensile performance of the INDUO-connection. Based on the experience and results gained during the project, future research on the performance and strength properties of the INDUO-connector should investigate the following: Type of loading: • Investigation of connection behavior under cycling loading; information for the design of dynamically loaded structures, e.g. caused by traffic, earthquake or wind. • Transverse loading of INDUO-connection: Influence of different member materials on shear capacity. Different member materials: Tensile and transverse connection capacity of • LVL with cross-plies (KertoQ of Finnforest) • Other solid wood species (Hemlock, SPF, etc.) Alternative lamination methods of timber halves using: • Nails (smooth nails, annular ringed or helically threaded nails) • Truss-plates Alternative configuration of connector: • Investigation of tensile strength and performance with a connector body made of mild steel (manufactured by point-welding steel dowels to steel connector body) • Increasing number of load-bearing pins by serially connecting two (or IV2) type B connectors irtoduo List of References 88 7 List of References American Society of Civil Engineers. (1996). "Standard for Load and Resistance Factor Design for Engineered Wood Construction - ASCE 16-95", ASCE, New York, NY, USA American Society for Testing and Materials. (1996). "Standard Methods of Testing Small Clear Specimens of Timber - D143-83", ASTM, Philadelphia, PA, USA American Society for Testing and Materials. (1996). "Standard Test Methods for Mechanical Fasteners in Wood - D1761-88", ASTM, Philadelphia, PA, USA American Society for Testing and Materials. (1996). "Standard Test Methods for Specific Gravity of Wood and Wood-Base Materials - D2395-93", ASTM, Philadelphia, PA, USA American Society for Testing and Materials. (1996). "Standard Specification for Evaluation of Structural Composite Lumber Products - ASTM D5456-93", ASTM, Philadelphia, PA, USA American Society for Testing and Materials. (1996). "Standard Test Methods for Mechanical Fasteners in Wood - ASTM D1761-88", ASTM, Philadelphia, PA, USA American Society for Testing and Materials. (1996). "Standard Test Methods for Bolted Connections in Wood and Wood-Base Materials - ASTM D5652-95", ASTM, Philadelphia, PA, USA American Society for Testing and Materials. (1997). "Standard Test Method for Evaluating Dowel-Bearing Strength of Wood and Wood-Base Products -ASTM D5764a-97", ASTM, Philadelphia, PA, USA BlaB, H.J. (2001). Expert's report: "Optimierung des INDUO-Verbundankers; Zusammenfassung der Gutachten / Typenstatik", Ingenieurburo BlaB & Eberhart, Karlsruhe, Germany Buchanan, A., Moss, P., Eistetter, S.. (2000). "Cement Grouted Steel Bars in Glulam", Proceedings, 6th World Conference on Timber Engineering, Whistler, BC Canadian Standards Association. (1994). "Engineering Design in Wood (Limit States Design) - CAN/CSA-086.1-94", CSA, Rexdale, Ontario, Canada incduo List of References 89 Canadian Wood Council. (1995). "Wood Design Manual 1995", Canadian Wood Council, Ottawa, Ontario, Canada Canadian Wood Council. (1999). "Introduction to Wood Design", Canadian Wood Council, Ottawa, Ontario, Canada Deutsches Institut fur Bautechnik. (2002). 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"Eurocode No. 5: Design of Timber Structures, Part 1 -1: General Rules und Rules for Buildings", CEN, Brussels, Belgium European Committee for Standardization. (1997). "EN 1562 - Founding - Malleable Cast Irons; CEN, Brussels, Belgium European Committee for Standardization. (1997). "EN 1563 - Founding - Spheroidal Graphit Cast Irons", CEN, Brussels, Belgium European Committee for Standardization. (1993). "EN 383 - Timber structures; test methods; determination of embedding strength and foundation values for dowel type fasteners", CEN, Brussels, Belgium Fiihrer, W. (2002). Expert's report: "Enwicklung einer montagefreundlichen Werkzeuglosung fur die ruckwartige INDUO-Verbundanker-Verschraubung", RWTH Aachen, Aachen, Germany inoduo List of References 90 Giildenpfennig, J. (1997). Expert's report: "Stellungnahme zur Einhaltung der Anforderungen an einen genehmigungsfahigen Standsicherheitsnachweis von Einfamilienhausern in Selbstbauweise unter Verwendung von Kreuzbalken mit INDUO-Verbundankern", RWTH Aachen, Aachen, Germany Johansen, K.W.. (1949). 'Theory of timber connections", InternationahAssociationof Bridge and Structural Engineering, Bern, Switzerland Kangas, J.. (2000). "Design of connections based on in V-form glued-in rods", Proceedings, 6th World Conference on Timber Engineering, Whistler, BC Mischler, A., Prion, H., Lam, F.. (2000). "Load-carrying Behavior of Steel-to-Timber Dowel Connections", Proceedings, World Conference of Timber Engineering 2000, Whistler, BC Madsen, B. .(1998). "Reliable timber connections.", North Vancouver, BC, Canada National Research Council Canada. (1984), "CCMC Evaluation Report, CCMC 08675-R -Microllam™ LVL", Canadian Construction Materials Centre, Ottawa, Ontario, Canada National Research Council Canada. (1986), "CCMC Evaluation Report, CCMC 11161-R-Parallam® PSL", Canadian Construction Materials Centre, Ottawa, Ontario, Canada National Research Council Canada. (1994), "CCMC Evaluation Report, CMC 12627-R-TimberStrand®,LSL", Canadian Construction Materials Centre, Ottawa, Ontario, Canada Riberholt, H.. (1988). "Glued bolts in Glulam", Dept of Structural Engineering, Technical University of Denmark, Lyngby, Denmark Schneider, Klaus-Jurgen (1998). "Bautabellen fiir Ingenieure", Werner Verlag, Dusseldorf, Germany Schreyer, A., Bathon, L., Prion, H.G.L.. (2000). "Determination of the Capacities of a new Composite Timber-Steel Connector System", Proceedings, 6th World Conference on Timber Engineering, Whistler, BC Smith, I., Foliente, G.. (2002). "Load and Resistance Factor Design of Timber Joints: International Practice and Future Direction", Journal of Structural Engineering, Vol. 128, No.1 incduo List of References 91 Turkovskij, S. B.. (1991). "Use of Glued-in Bars for Reinforcement of Wood Structures", Proceedings, 1991 Timber Engineering Conference, London, UK Wisconsin Department of Commerce, Safety & Buildings Division. (2002). Building Products Evaluation, Evaluation # 200216-0, "Bertsche System - Concealed Forged Steel Heavy Timber Connection System", Wisconsin Department of Commerce, Madison, Wl; USA inoduo Appendices 92 8 Appendices 8.1 Photographic documentation 8.1.1 Manufacturing steps of test specimen Figure 95: Cutting timber members to Figure 96: Planing of timber members to final rough dimensions (Sliding Table Saw) width and thickness (4-Sided Planer) Figure 97: Machining of rows of holes and Figure 98: Machining of circular grooves V-groove by means of CNC-router (CNC-router) irvoduo Appendices 93 Figure 99: INDUO-connector ready to be Figure 100: Circular grooves to accommodate embedded in machined timber halves Steel Side Plates Figure 101: Applying PVA-construction glue to Figure 102: Inserting the connector in V-groove both inside faces of the timber halves inoduo Appendices 94 Figure 103: Joining of both timber halves Figure 104: Inserting the composite member enclosing the connector into hydraulic press; Pressing time: 30 minutes Figure 105: Alternative connection of timber Figure 106: Setup of screws halves with regular wood-screws 6x10 Figure 107: Tapering of the test member to squared cross-section 100x100 and 120x120mm respectively (NC-shaper) incduo 8.1.2 Test procedure Appendices 95 Figure 108: Specimen ready to be tested Figure 109: Stacked members of different connector-material setups before testing Figure 110: Specimen connected to upper Figure 111: Steel Side Plates transfer applied machine support load from the lower machine support to test member inoduo Appendices 96 Figure 112: Assembly of Steel Side Plates Figure 113: Close-up of steel rings sliding with 7/8-inch bolts into circular groove Figure 114: Steel Side Plates are pressed into grooves by means of regular clamps inoduo Appendices 98 Figure 118: Test apparatus consisting of test machine, control unit and PC Figure 120: Gallow in place to support the test member after being uncoupled Figure 119: Unloading of heavy test member by means of a "mobile gallow" Figure 121: Disassembling of upper and lower couplings incduo Appendices 99 Figure 122: Tested type A and B specimens, 120x120mm, test series 1 Figure 123: Tested type A and B specimens, 100x100mm, test series 1 Figure 124: Tested connector-type-B specimens, 100x100mm, test series 2 irvoduo Appendices 100 8.1.3 Failure modes TimberStrancfLSL Figures125a-e: No failure observed with TB-member setups incduo Appendices 101 inoduo Appendices 102 irroduo Appendices 103 inoduo Appendices 104 Douglas Fir Figures 129a-g: Failure modes observed with DB-member setups incduo Appendices 105 Figures 130a-c: Failure modes observed with DA-member setups inoduo Appendices 106 iroduo Appendices 107 Figures 132a-d: Failure modes observed with MA-member setups inoduo Appendices 108 ParallarrfTSL incduo Appendices 109 inoduo Appendices 110 8.2 Calculations RELAN Data Fitting (Error of Distribution Fit) Normal Lognorm. 2P-WOID. 3P-Woib. DG Fir 0.0278 0.0333 0.0154 0.0154 PSL 0.0016 0.0019 0.0029 0.C014 LVL 0.0095 0.0082 0.0161 0.0051 Parameters of Fitted Distribution Normal Lognorm. 2P-Welh 3P-Wolb. mean std. dev. mean std. dev. loe m k loe m k DG Fir 168.078 15.867 168.066 15.315 0 174.962 12.608 0.000 1742962 12:608 PSL 157.821 13.419 157.920 13.489 0 163.278 14.469 113.000 49.602 3 787 LVL 152.956 12.017 153.083 12.320 0 157.642 16.089 134.655 1.485 5th percentile strength [kN Characteristic value of maximum tensile capacity [kNl Normal >• Lognorm. Normal - Loqnorm. 2P-Weib. 3P-Woib. LSL (180100) LSL (144.00) DG Fir 141.98 144.75 138.24 138.24 DG Fir 113.58 115.80 110.59 110.59 PSL 135.75 137.98 132.98 135164 PSL 108.60 110.39 106.38 108.51 LVL 133.19 133.81 131.07 137S48 LVL 106.55 107.05 104.85 109)98 Table 15: RELAN data fitting of strength data set RELAN Data Fitting (Error of Distribution Fit) WHO Normal Loqnorm 2P-Woib. 3P-Weib LSL 0.5306 0.2042 0.3935 0.1346 DG Fir 0.3923 0.0656 0.2408 0.0547 PSL 1.8531 1.1627 1.5708 '• >\ 0.6728'. , .-LVL 2.1072 0.6898 1.0657 0r48331 Parameters of Fitted Distribution 10/40 «S«iiNorrnal Lognorm. 2P-Weib 3P-Weib. mean std. dev. mean std. dev. loe m k loe m k LSL 152,205 59,325 166,861 91,702 0 179,855 2.3629 68,005 103:262 1.0557 DG Fir 109,185 44,933 121,628 74,088 0 129,734 2.2292 391332 86,376 1.1431 PSL 149,511 65,389 211,144 197,957 0 192,074 1.8238 73,562 93 711 . 0.3895 LVL 121,317 58,466 182,918 193,393 0 182,318 1.2918 34.438 1381028 0.8366 5th percentile stiffness [N/mm] Characteristic value of maximum stiffness (10/40) 10140 Normal Lognorm. 2P-Wiib. 3P-Weib. mmmom. Normal Lognormal 2P-Weibull 3P-Weibull LSL 54,615 62,809 51,169 74.200 LSL 43,692 50,248 40,935 59,360 DG Fir 35,270 41,227 34,229 451758 DG Fir 28,216 32,981 27,383 36,606 PSL 41,946 41,710 37,687 731608 PSL 33,557 33,368 30,149 58,886 LVL 25,140 30,231 18,292 381402 LVL 20,112 24,185 14,634 30,721 RELAN Data Fitting (Error of Distribution Fit) 30/70 Normal Lognorm. 2P-Woib. 3P-Weib. LSL 0.1106 0.0791 0.1229 0.0666"' • DG Fir 0.2077 0.0050 0.1789 0.0228 PSL 0.2076 0.1145 0.2321 0 0493 LVL 0.1732 0.0267 0.1251 -. 0.0255 Parameters of Fitted Distribution 30/70 Normal Lognorm. 2P-Wcib. 3P-Weib. mean std. dev. mean std. dev. loe m k loe m k LSL 133,047 33,671 134,782 37,716 0 145,792 4.4479 74.887 67,382 1.6409 DG Fir 163,499 55,744 171,960 75,428 0 185,950 2.9882 79,608 > • 99,783 1.2004 PSL 148,250 38,677 152,587 48,879 0 162,911 4.2402 99,326 ' , * 55,783 0.9514 LVL 134,873 49,839 142,501 68,877 0 154,646 2.7265 52J263 98,391 1.3729 5th percentile stiffness [N/mm] 30/70 Normal* Bllbqnorm.' 2P?Weib. : 3P-Weib.«-LSL 77,658 82,623 74,769 85.913 DG Fir 71,800 78,982 68,820 88;012 PSL 84,626 86,900 80,860 101,784 LVL 52,888 60,378 52,027 6j>B71 Table 16: RELAN data fitting of stiffness data set inoduo Appendices 111 Metric units Imperial units (inch, lbs, psi) PSL, 2.0E l)psii|n strength (factored resistance) • No group rcriuctiun factor No rRsist.ince .•' modification factor Adjustment of embedding strength Clididctersitii; vdlue for tonsils capacity Charact. tensile strength of wood (N/mm2): Ft 15.5 2,250 DIN 1052-2000 74,378 105,551 116,106 *> 116,106 MOE of wood (N/mm2): E 13,790 2,000,000 ECS ' 89,323 1111,019 Equivalent spec, gravity pSG 0.50 0.50 —* i lu.ujy of wood (a/cm") CSA 086.1 23,528 54,332 77,617 94,795 r .... — !H,/SS Embedding length main member (mm): L2 14.0 0.551 ASCE 16-95 69,257 73,400 112,923 Embedding length side L1 33.0 1.299 * member (mm): Pin diameter (mm): d 8.0 0.315 Spacing axial (mm): a1 40.4 1.591 Spacing perp.(mm): a2 25.0 0.984 End distance loaded edqe (mm): a3 80.0 3.150 Edge distance (mm) a4 37.5 1.476 DIN 1052-2000 CSA 086.1 Factor accounting for DOLand MC: k mod 0.8 Resistance factor: PHI 0.7 Partial factor for steel in timber connections: gamma m 1.1 Embedding strength wood (N/mm2): f 1 29.0 Charact. ultim. tensile strength of steel dowel (N/mm2): f u,k 500 Specific gravity / mean oven-dry density (g/cnf1): G 0.5 Charact. yield moment of steel dowel (Nmm): M y,k 35.6B9 Embedding strength steel main member (- infinite) (N/mm2): f2 10000 Charact. embedding strength wood (N/mm1): fh,D,k 37.72 Bolt yield strength (N/mm2): fy 320 Charact. embedding strength mod (N/mm2): f h,k 32.04 Number of shear planes: n s 2 Modification factor spacing / emb. strength: k a 0.85 Number of fasteners: nF 12 Factor for effective n: n ef 4.23 Factor for 2 to 12 fasteners in a row: JG 0.54 Factor for laoded end distance: J L 1.00 Charact. Load-carrying capacity per shear plane, per fastener (N): R k . : 6,047 Factor for number of rows: J R 0.80 JG*JL*JR = J F 0.43 ECS 11 = 28.4 11 = 36.97 Factor accounting for DOL and MC: k mod 0.8 Failure Mode I Lateral resistance per shear plane, per fastener (N): pU 6,121 8,155 Partial factor for wood and wood composites: gamma m,w 1.3 Failure Mode II Lateral resistance per shear plane, per fastener (N): pU 3,234 3,950 Partial factor for steel in timber connections: gamma m 1.1 KD = KT= KST= 1 pU=PU Charact. ultim. tensile strength of steel dowel (N/mm2): fu.k 500 f 1 = 38.61 A Charact. yield moment of steel dowel (Nmm): M y,k 34,133 t r • Charact. embedding strength wood (N/mm2): fh,0,k 37.72 Charact. embedding strength mod (N/mm2): fh.k 32.04 ASCE 16-95 Modification factor spacing / emb. strength: k a 0.85 Resistance Factor Connection: PHI z 0.65 Factor for effective n: n ef = n 6 Time effect factor: lamda 0.80 Dowel bending yield strength (psi): F yb 60,000 Failure Mode 1 Design value of the load-carrying capacity per shear plane, per fastener (N): R d 5,205 L m (in): L2 0.55 Failure Mode II Design value of the load-carrying capacity per shear plane, per fastener (N): Rd 722 L s (in): L1 1.30 Failure Mode II Lateral resistance per shear plane, per fastener (gamma m =1) (N): R d 4,585 Embedding strength steel main member (- infinite) (psi): F em 1,450,000 Embedding strength wood side member (psi): F es 5,600 Lm/Ls= Rt 0.42 F em / F es = R e 258.93 Imperial units Metric units (N) Failure mode I: Nominal lateral design value for a single fastener (lbs): Zl 3,804 16,921 Failure mode II: Nominal lateral design value for a single fastener (lbs): Zll 2,644 11,763 Factor failure mode II: k3 0.56 MC factor: C m 1 Temperature factor: Ct 1 Group action factor Cg 0.944 MOE steel (psi): E m 30,458,000 MOE wood (psi): E s 2,000,000 R EA REA 0.155 X-section main member (in2): A m 2.170 X-section side members (in2): As 5.115 spacing (in): s 1.590 Slip modulus in dowel-type wood-to-steel connections: gamma 47,725 u 1.004 m 0.912 Number of fasteners in a row: n 6 Number of fast, rows: n r 2 Tot. number of fast.: n F 12 Table 17: Calculation of characteristic strength values; PSL inoduo Appendices 112 Imperial units {inch, lbs, Metric units psi) Douglas Fir ' '• No.1 & better Design slienylh ^(factored ; resistance)' No group reduction factor ("Kg" = 1) No lesistanrc1 modification f<tctur ("PHI" = 1) • Adjustment Df embedding, strength Lhdriictersitic value for tensile capacity Charact. tensile strength of wood (N/mm2): Ft 8.1 1,175 DIN 1052-2000 73,630 104,490 114,939 MOE of wood (N/mm2): E 10,500 1,522,896 EC5 88,137 -*• 108,513 1011.513 Density of wood (g/cm3): P 0.49 0.49 CSA 086.1 23,203 53,582 76,546 91,941 V •11,941 Embedding length main member (mm): L2 14.0 0.551 ASCE 16-95 67,042 72,409 111,398 • ni.ua Embedding length side member (mm): L1 33.0 1.299 Pin diameter (mm): d 8.0 0.315 Spacing axial (mm): a1 40.4 1.591 Spacing perp.(mm): a2 25.0 0.984 End distance loaded edge (mm): a3 80.0 3.150 Edge distance (mm) a4 37.5 1.476 DIN 1052-2000 CSA 086.1 Factor accounting for DOL and MC: k mod 0.8 Resistance factor: PHI 0.7 Partial factor for steel in timber connections: gamma m 1.1 Charact. ultim. tensile strength of steel dowel (N/mm2): fu.k 500 Embedding strength wood (N/mm2): f 1 28.4 Charact. yield moment of steel dowel (Nmm): M y,k 35,669 Specific gravity / mean oven-dry density (g/cm3): G 0.49 Charact. embedding strength wood (N/mm2): f h.Q.k 36.97 Embedding strength steel main member (- infinite) (N/mm2): f2 10000 Charact. embedding strength mod (N/mm2): f h,k 31.40 Bolt yield strength (N/mm2): fy 320 Modification factor spacinq / emb. strenqth: k a 0.85 Number of shear planes: n s 2 Factor for effective n: n ef 4.23 Number of fasteners: n F 12 Factor for 2 to 12 fasteners in a row: J G 0.54 Charact. Load-carrying capacity per shear plane, per fastener (N): R k 986 Factor for laoded end distance: J L 1.00 EC5 Factor for number of rows: J R 0.80 JG*JL*JR = J F 0.43 Factor accounting for DOL and MC: k mod 0.8 11 = 28.4 11 = 36.97 Partial factor for wood and wood composites: (gammam.w 1.3 Failure Mode 1 Lateral resistance per shear plane, per fastener (N): pU> 5.998 7.808 Partial factor for steel in timber connections: gamma m 1.1 Failure Mode II Lateral resistance per shear plane, per fastener (N): pU 3,189 illiiililtiitii! 3,831 Charact. ultim. tensile strength of steel dowel (N/mm2): fu.k 500 KD = KT = KST = 1 pU = PU Charact. yield moment of steel dowel (Nmm): M y.k 34,133 f 1 = 36.97 Charact. embedding strength wood (N/mm2): fh,0,k 36.97 Charact. embedding strength mod (N/mm2): fh.k 31.40 ASCE 16-95 Modification factor spacing/ emb. strength: k a 0.85 Resistance Factor Connection: PHI z 0.65 Factor for effective n: n ef = n 6 Time effect factor: lamda 0.80 Dowel bending yield strenqth (psi): F yb 60,000 Failure Mode I Design value of the load-carrying capacity per shear plane, per fastener (N): Rd 5,101 L m (in): L2 0.55 Failure Mode II Design value of the load-carrying capacity per shear plane, per fastener (N): R d . C- 3,672 L s (in): L1 1.30 Failure Mode II Lateral resistance per shear plane, per fastener (gamma m =1) (N): R d 4,521 Embedding strength steel main member (~ infinite) (psi): F em 1,450,000 Embedding strength wood side member (psi): F es 5,500 Lm/Ls= Rt 0.42 F em / F es = R e 263.64 Imperial units Metric units (Nj Failure mode I: Nominal lateral design value for a single fastener (lbs): Zl 3.736 16,619 Failure mode II: Nominal lateral design value for a single fastener (lbs): Zll 2,609 ' 11,604 Factor failure mode II: k3 0.56 MC factor: C m 1 Temperature factor: Ct 1 Group action factor: Cg 0.926 MOE steel (psi): E m 30,458,000 MOE wood (psi): E s 1,522,896 REA R EA 0.118 X-section main member (in2): A m 2.170 X-section side members (in2): As 5.115 spacinq (in): s 1.590 Slip modulus in dowel-type wood-to-steel connections: gamma 47,725 u 1.005 m 0.901 Number of fasteners in a row: n 6 Number of fast, rows: n r 2 Tot. number of fast.: n F 12 Table 18: Calculation of characteristic strength values; Douglas Fir incduo Appendices 113 Imperial units (inch, lbs, Metric units psi) LVL, ' at Design strenqth (factored resistance) No group ; No lesistance / Adjustment ol reduction factor: modification factor ' embedding ("Kg" = 1) ("PHI"=1) strength Charactersitic value fur tensile capacity Charact. tensile strength of wood (N/mm2): Ft 12.4 1,805 DIN 1052-2000 74,378 105,551 116,106 116,106 MOE of wood (N/mm2): E 13,100 1,900,000 ECS 89,323 -*• 110,039 110,039 Equivalent spec, gravity of wood (q/cm2) p SG 0.50 0.50 CSA 086.1 23,528 54,332 77,617 94,795 94,795 Embedding length main member (mm): L2 14.0 0.551 ASCE1635 69,034 73,400 112,923 112.923 Embedding length side member (mm): L1 33.0 1.299 Pin diameter (mm): d 8.0 0.315 Spacing axial (mm): a1 40.4 1.591 Spacing perp.(mm): a2 25.0 0.984 End distance loaded edqe (mm): a3 80.0 3.150 Edge distance (mm) a4 37.5 1.476 DIN 1052-2000 CSA 086.1 Factor accounting for OOL and MC: k mod 0.8 Resistance factor: PHI 0.7 Partial factor for steel in timber connections: gamma m 1.1 -Charact. ultim. tensile strength of steel dowel (N/mm2): f u,k 500 Embedding strength wood (N/mm2): f 1 29.0 Charact. yield moment of steel dowel (Nmm): M y.k 35,669 Specific gravity./ mean oven-dry density (g/cm2): G 0.5 Charact. embedding strength wood (N/mm2): fh,0,k 37.72 Embedding strength steel main member (- infinite) (N/mm2): f2 10000 Charact. embedding strength mod (N/mm2): f h,k 32.04 Bolt yield strength (N/mm2): fy 320 Modification factor spacing / emb. strength: k a 0.85 Number of shear planes: n s 2 Factor for effective n: n ef 4.23 Number of fasteners: n F 12 Factor for 2 to 12 fasteners in a row: JG 0.54 Charact. Load-carrying capacity per shear plane, per fastener (N): R k 6,047 Factor for laoded end distance: J L 1.00 ECS Factor for number of rows: J R 0.80 JG*JL*JR = JF 0.43 Factor accounting for DOL and MC: k mod 0.8 11 = 28.4 f1 = 36.97 Partial factor for wood and wood composites: gamma m,w 1.3 Failure Mode I Lateral resistance per shear plane, per fastener (N): pU '6,121 8.155 Partial factor for steel in timber connections: gamma m 1.1 Failure Mode II Lateral resistance per shear plane, per fastener (N): pU 3,234 3.950 Charact. ultim. tensile strength of steel dowel (N/mm2): f u,k 500 KD = KT = KST = 1 p U= P u Charact. yield moment of steel dowel (Nmm): M y,k 34,133 f 1 = 38.61 Charact. embedding strength wood (N/mm2): fh.O.k 37.72 Charact. embedding strength mod (N/mm2): f h,k 32.04 ASCE 1635 Modification factor spacing / emb. strenqth: k a 0.85 Resistance Factor Connection: PHI z 0.65 Factor for effective n: n ef = n 6 Time effect factor: lamda 0.80 Dowel bending yield strength (psi): F yb 60,000 Failure Mode I Design value of the load-carrying capacity per shear plane, per fastener (N): R d 5,205 L m (in): L2 0.55 Failure Mode II Design value of the load-carrying capacity per shear plane, per fastener (N): R d 3,722 L s (in): L 1 . 1 30 Failure Mode II Lateral resistance per shear plane, per fastener (gamma m =1) (N): R d 4,585 Embedding strength steel main member (~ infinite) (psi): F em 1,450,000 Embedding strength wood side member (psi): F es 5,600 -Lm/Ls= Rt 0.42 F em / F es = Re 258.93 Imperial units Metric units (N) Failure mode I: Nominal lateral design value for a single fastener (lbs): Zl 3,804 16.921 Failure mode II: Nominal lateral design value for a single fastener (lbs): Zll 2,644 Factor failure mode II: k3 0.56 MC factor: C m 1 Temperature factor: Ct 1 Group action factor: Cg 0.941 MOE steel (psi): Em 30,458,000 MOE wood (psi): E s 1,900,000 R EA R EA 0.147 X-section main member (in2): A m 2.170 X-section side members (in2): As 5.115 spacing (in): s 1.590 Slip modulus in dowel-type wood-to-steel connections: gamma 47,725 u 1.004 m 0.910 Number of fasteners in a row: n 6 Number of fast, rows: n r 2 Tot. number of fast.: nF 12 Table 19: Calculation of characteristic strength values; LVL inoduo Appendices 114 Metric units Imperial units (inch, lbs, psil LSL, ! oL n<mu llillll Dcsiyn stionytli ^^^^is|aricS)^p Nu yruup reduction factor CK, -1, Nu it'MstdnLe / modification factor CPHI"=;I) . Adjustment ul inli Idin | •in nijlh Char.irtcrsitir value fur tensile capacity Charact. tensile strength of wood (N/mm2): Ft 13.4 1,950 l/V I II in IV V MOE of wood (N/mm2): E 10,342 1,500,000 DIN 1052-2000 64% 80,108 113,682 125,050 125,050 Equivalent spec, gravity pSG 0.58 0.58 of wood (g/cm3) EC5 81% 98,755 fe 171 1QO 172,191 Embedding length main L2 14.0 0.551 member (mm): CSA 086.1 25% 26,076 60,215 86,022 105.373 105,3/3 Embedding length side member (mm): L1 33.0 1.299 ASCE 16-95 60% 76,108 82,299 126,613 U6.613 Pin diameter (mm): d 8.0 0.315 Spacing axial (mm): a1 40.4 1.591 Spacing perp.(mm): a2 25.0 0.984 End distance loaded edge (mm): a3 80.0 3.150 Edge distance (mm) a4 37.5 1.476 DIN 1052-2000 CSA 086.1 Factor accounting for DOL and MC: k mod 0.8 Resistance factor: PHI 0.7 Partial factor for steel in timber connections: gamma m 1.1 Embedding strength wood (N/mm2): f 1 33.6 Charact. ultim. tensile strength of steel dowel (N/mm2): f u,k 500 Specific gravity / mean oven-dry density (g/cm3): G 0.58 Charact. yield moment of steel dowel (Nmm): M y,k 35,669 Embedding strength steel main member (- infinite) (N/mm2): f2 10000 Charact. embedding strength wood (N/mm2): f h.O.k 43.76 Bolt yield strength (N/mm2): fy 320 Charact. embedding strength mod (N/mm2): f h,k 37.16 Number of shear planes: n s 2 Modification factor spacing / emb. strength: k a 0.85 Number of fasteners: n F 12 Factor for effective n: n ef 4.23 Factor for 2 to 12 fasteners in a row: J G 0.54 Factor for laoded end distance: J L 1.00 Charact. Load-carrying capacity per shear plane, per fastener (N): R k 0 513 Factor for number of rows: J R 0.80 ECS JG *JL'JR = J F 0.43 Factor accounting for DOL and MC: k mod 0.8 f 1 = 28.4 f1 = 36.97 Partial factor for wood and wood composites: lamma m,\ 1.3 Failure Mode I Lateral resistance per shear plane, per fastener (N): pU 7,100 9,465 Partial factor for steel in timber connections: gamma m 1.1 Failure Mode II Lateral resistance per shear plane, per fastener (N): pU 3,584 4,391 Charact. ultim. tensile strength of steel dowel (N/mm2): f u.k 500 KD = KT= KST= 1 p U = P U i Charact. yield moment of steel dowel (Nmm): M y,k 34,133 fl = A 1 44.82 Charact. embedding strenqth wood (N/mm2): f h,0,k 43.76 I Charact. embedding strength mod (N/mm2): f h,k 37.16 ASCE 16-95 Modification factor spacing / emb. strenqth: k a 0.85 Resistance Factor Connection: PHI z 0.65 Factor for effective n: n ef = n 6 Time effect factor: lamda 0.80 Dowel bending yield strength (psi): Fyb 60,000 Failure Mode I Design value of the load-carrying capacity per shear plane, per fastener (N): R d 6,038 L m (in): L2 0.55 Failure Mode II Design value of the load-carrying capacity per shear plane, per fastener (N): R d 4,115 L s (in): L1 1.30 Failure Mode II Lateral resistance per shear plane, per fastener (gamma m =1) (N): R d 5,091 Embedding strength steel main member (- infinite) (psi): F em 1.450,000 Embedding strength wood side member (psi): F es 6,500 Lm/Ls= Rt 0.42 F em / F es = Re 223.08 Imperial units Wetn'c units (N) Failure mode I: Nominal lateral design value for a single fastener (lbs): Zl 4,415 19,640 Failure mode II: Nominal lateral design value for a single fastener (lbs): Zll 2,965 • 13,189 Factor failure mode II: k3 0.54 MC factor: C m 1 Temperature factor: Ct 1 Group action factor: Cg 0.925 MOE steel (psi): E m 30,458,000 MOE wood (psi): E s 1,500,000 REA R EA 0.116 X-section main member (in2): A m 2.170 X-section side members (in2): As 5.115 spacing (in): s 1.590 Slip modulus in dowel-type wood-to-steel connections: gamma 47,725 u 1.006 m 0.900 Number of fasteners in a row: n 6 Number of fast, rows: n r 2 Tot. number of fast.: n F 12 Table 20: Calculation of characteristic strength values; LSL 

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