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UBC Theses and Dissertations

Oak Street Bridge half bent test on as built and retrofitted specimens Arambawela, Udhaya S. 1994

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Oak Street Bridge Half Bent TestOn As Built and Retrofitted SpecimensbyUdhaya S. Arambawela.B.Eng. (Civil), University of Birmingham, Birmingham,England 1991A THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTHE REQUIREMENTS FOR THE DEGREEE OFMASTER OF APPLIED SCIENCEinTHE FACULTY OF GRADUATE STUDIESDEPARTMENT OF CIVIL ENGINEERINGWe accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIAJune 1994Udhaya Arambawela, 1994In presenting this thesis inpartial fulfilment of therequirements for an advanceddegree at the Universityof British Columbia, I agreethat the Library shall makeitfreely available for referenceand study. I further agreethat permission for extensivecopying of this thesisfor scholarly purposesmay be granted bythe head of mydepartment or by hisor her representatives. Itis understood thatcopying orpublication of this thesis forfinancial gain shallnot be allowed withoutmy writtenpermission.Department ofcf\”ILiiN4The University of British ColumbiaVancouver, CanadaDatezc AP/ZIL 9DE-6 (2188)IIABSTRACTAs part of a research program on the seismic behaviour and retrofit of existingbridges, this investigation was designed to focus on column-cap beam joint regions.During the initial planning stages, a related investigation was sponsored by the Ministry ofTransportation and Highways of BC to perform slow cyclic loading on large scale modelsof the Oak St. Bridge two-column bents. Therefore it was decided that this investigationwould focus on the column-cap beam joints of the Oak St. Bridge, so that the resultswould have applicability to the actual bridge, and at the same time comparisons would beavailable between the joint tests of this investigation, and the full bent tests of the Ministryinvestigation. The joint tests described in this investigation comprise tests of half the twocolumn bent, or “half bent test”.This investigation consists of the design of a test frame suitable for the half benttests and other in plane load tests on structural assemblies such as concrete joints and theirconnecting members, a slow cyclic test on a 0.45 scale model of half of one of the Oak St.Bridge bents as originally constructed, and a slow cyclic test on a similar model retrofittedby post-tensioning. The latter duplicates one of the retrofit schemes also tested in theMinistry sponsored program on a 0.45 scale model of the full bent.The test frame proved suitable for the test program and for similar future testing.With a variety of options available for application of in-plane loading and restraints, it iscapable of testing large scale specimens of realistic sizes for bridges and buildings. In thetests described in this thesis, it demonstrated the potential ability to duplicate the essentialbehaviour of the more expensive full bent tests.IIIAbstract iiList of Tables ViList of Figures viiAcknowledgement xi1 Introduction 11.1 11.2 21.3 31.4 51.5 121.6 131.7 152 Analysis and Design of the Test Frame 172.1 Introduction 172.2 Capacities of the Frame 193 Test Specimen 253.1 Introduction 253.2 Properties of the Prototype Bent 253.3 Properties of the UBC Full Bent Model 263.4 Properties of the Half Bent Model 263.5 Construction of the Specimen 323.5.1 Formwork 323.5.2 Reinforcing Steel 34TABLE OF CONTENTSBackgroundObjectives and the Scope of InvestigationTest FacilityChoice of Prototype StructureSeismic deficiencies of the Oak Street bentsConcept of Joint PerformanceJoint MechanismIv3.5.3 Concrete 364 Instrumentation and Data Acquisition Systems 414.1 Introduction 414.2 Instrument Locations 454.2.1 Strain Gauge Locations 454.2.2 LVDT Locations 495 Testing Procedure 525.1 Boundary Conditions 525.2 Loading Sequences 585.3 Loading on the Full Bent Model 585.4 Loading on the the Specimen OJ1 595.5 Loading on the Specimen 032 666 Experimental Obserations 736.1 Specimen OJ1 736.1.1 Observed Behaviour 736.1.2 Sectional Analysis 786.1.3 Strain Gauge Readings 806.2 Specimen 0J2 826.2.1 Observed Behaviour 826.2.2 Sectional Analysis 856.2.3 Strain Gauge Readings 886.3 Comparison with Bent Test Results 907 Summary and Conclusions 96References 100Appendix A: Analysis and Design of The Test Frame 104Appendix B: Force Resultants of OJ and OSB Specimens 107Appendix C: Jack Forces of J2 and J3 115VVILIST OF TABLESTable PageTable 3.1 Concrete properties of 031 36Table 3.2 Concrete properties of 032 37Table 4.1 Strain gauge channel numbering 46Table 4.2 Strain gauge locations 47Table 5.1 Jack 31 loading for specimen 031 62Table 5.2 31 Loading for specimen 032 69Table 6.1 031 Maximum demand for pulling 78Table 6.2 Maximum demand for pushing 78Table 6.3 Input loading 031 joint 7 79Table 6.4 Out put capacities 031 joint 7 79Table 6.5 Maximum demand for pulling 86Table 6.6 Maximum demand for pushing 86Table 6.7 Input loading 0J2 joints 7 and 11 87Table 6.8 Output capacities 032 joints 7 and 11 87Table A. 1 Maximum frame member forces 106TableC.1 JackJ2 mm/max load 115Table C.2 Jack 32 and 33 mm/max load 115VIILIST OF FIGURESFigure PageFig. 1.1 Photograph of the Oak St. Bridge 6Fig. 1.2 General arrangement7Fig. 1.3 Bent S28-reinforcing details of prototype (Elevation) 9Fig. 1.4 Bent S28 reinforcing details of prototype (Plan)10Fig. 1.5 Bent S28 reinforcing details prototype (Sections) 11Fig. 1.6 Compression strut mechanism 16Fig. 1.7 Truss mechanism 16Fig. 2.1 Basic specimen configurations 18Fig. 2.2 Final magnitudes and ranges ofjack loads (inside of frame) 20Fig. 2.3 Construction drawing (Elevation)21Fig 2.4 Construction drawing (Plans)22Fig. 2.5 Construction drawing (Connections)23Fig. 2.6 Photo of the steel frame24Fig. 3.1 Specimen OJ1 27Fig. 3.2 Specimen OJ2 28Fig. 3.3 MOTH model elevation 29Fig. 3.4 MOTH model plan 30Fig. 3.5 MOTH model sections 31Fig. 3.6 A photograph of the form work 33Fig. 3.7 A photograph of the steel cages 35Fig. 3.8 Photograph showing pouring of the concrete 38Fig. 3.9 Post-tensioning of bars 39Fig. 3.10 Installing the specimen in the frame 40VIIIFig. 3.11 Specimen and the frame .40Fig. 4.1 Photograph of a strain gauge in a bar 43Fig. 4.2 Photo of the data acquisition system 44Fig. 4.3 Strain gauge locations (Elevation) 48Fig. 4.4 Strain gauge locations (Plan) 49Fig. 4.5 LVDT locations 50Fig. 4.6 Photo of LVDT locations 51Fig. 5.1 Specimen OJ1 bearing locations 53Fig. 5.2 Specimen 0J2 bearing locations 54Fig. 5.3 Bearing arrangement 55Fig. 5.4 Photograph of the pin bearing 56Fig. 5.5 Horizontal and vertical jack connection 57Fig. 5.6 Dead and lateral loads on full bent test 59Fig. 5.7 Loading 031 60Fig. 5.8 Applied jack loads specimen OJ1 63Fig. 5.9 Shear/Moment variation of 031 cap beam 64Fig. 5.10 Cap beam shear of specimen 031 and OSB1 64Fig. 5.11 Loading 0J2 67Fig. 5.12 Applied jack loads specimen 0J2 70Fig. 5.13 Shear /Moment variation at x-x of 032 71Fig. 5.14 Cap beam shear of specimen 0J2 and OSB2 71Fig. 5.15 Column shear of specimen 032 and OSB2 72Fig. 6.1 031 Load displacement at the column tip 75Fig. 6.2 Photograph of crack patterns at sequence F 75Fig. 6.3 Photograph of crack patterns at sequence 0 76IxFig. 6.4 Photograph of crack patterns at sequence P 76Fig. 6.5 Load displacement at the column tip (Column Test) 77Fig. 6.6 Photograph of crack patterns at Push Over 77Fig. 6.7 Strain gauge BB3 81Fig. 6.8 0J2 Load displacement at the column tip 83Fig. 6.9 Photograph of crack patterns at sequence D 83Fig. 6.10 Photograph of crack patterns at sequence L 84Fig. 6.11 Photograph of crack patterns at Push Over 84Fig. 6.12 Photograph of crack patterns at Push over 85Fig. 6.13 Strain gauge C04 88Fig 6.14 Strain gauge C13 89Fig 6.15 Hysteresis loop of bent test 2 (OSB2) 90Fig.6. 16 Cap beam cracking specimen OJ1 92Fig. 6.17 Cap beam cracking Specimen OSB1 92Fig. 6.18 Crack pattern of OJ1 and OSB1 93Fig. 6.19 Column cracking specimen 0J2 94Fig. 6.20 Column cracking specimen OSB2 95Fig. B. 1 Maximum loading on OJ1 107Fig. B.2 Maximum loading on OSB1 107Fig. B.3 Axial force on OJ1 108Fig. B.4 Axial force on OSB1 108Fig. B.5 Shear force on OJ1 109Fig. B 6 Shear force on OSB1 109Fig. B.7 Bending moment on OJ1 110Fig. B.8 Bending moment on OSB1 110xFig. B.9 Maximum loading on 0J2.111Fig. B 10 Maximum loading on OSB2 111Fig. B 11 Axial force on 032 112Fig. B 12 Axial force on OSB2 112Fig. B. 13 Shear force on 032 113Fig. B. 14 Shear force on 05B2 113Fig. B 15 Bending moment on 0J2 114Fig. B.16 Bending moment on 05B2 114XIACKNOWLEDGEMENTThe author is very grateful to his supervisor, Professor R. G. Sexsmith for hisguidance, suggestions and encouragement extended throughout his research. The financialsupport provided by the Natural Sciences and Engineering Research Council of Canada,Ministry of Transportation and Highways of British Columbia, and the University ofBritish Columbia is also greatfhlly acknowledged. The author also wishes to express hisgratitude to Professors P.E. Adebar and D.L. Anderson for reviewing the manuscript.Appreciation is extended to Mr. Dick Postgate, Mr. Paul Symons, Mr. MarkusSeethaler and Ms.Dongchang Gao for their helpful participation and assistance during theexperimental investigation.The author also wishes to thank his parents for their moral and financial supportthroughout his University career, and the friends for sharing laughs and making life easier.CHAPTER 1INTRODUCTION1.1 BackgroundSouthern coastal British Columbia is situated over the Cascadia Subduction zone.Earthquakes that may present a hazard to this area may occur in three distinct sourceregions: deep earthquakes within the subducted plate, earthquakes within the continentalcrust, and subduction earthquakes on the boundaiy layer between the two lithosphericplates (Rogers, 1993).The recent history of the area includes a number of earthquakes up to Richtermagnitudes about 7, but these have occurred relatively far from urban areas and have notbeen the cause of widespread damage. The rapid growth of population and correspondingdevelopment has increased the potential for serious damage.The response and the magnitude of damage to a structure due to an earthquakedepends on a number of parameters:1. Magnitude and location of the earthquake2. Duration of strong shaking3. The geology and soil conditions of the site4. The level of earthquake resistant construction12Of the above four, only the soil and the construction, in particular the strength andductility of the structure, can be improved.As a result of the 1971 San Fernando, 1987 Whittier Narrows and 1989 LomaPrieta earthquakes, the importance of upgrading the bridge structures was demonstrated.In the case of two column bridge bents, shear failure of the beam, column or beam-columnjoint are possible failure modes which may have to be rectified to achieve acceptableperformance of the complete structure.Most of the major bridges in southern coastal British Columbia were built prior to1970, when the knowledge of seismic design was very low. Preliminary assessment andscreening of British Columbia’s bridges indicates that a great many require seismicupgrades (MOTH, 1992). Because these structures were designed and constructed undera variety of now obsolete criteria, they pose many problems in the analysis of theirbehaviour and design of retrofits.1.2 OBJECTIVES AND THE SCOPE OF INVESTIGATIONThis project has been developed to assist in the prediction of behaviour of originaland retrofitted structures, particularly near the joint regions of reinforced concrete bridgesupport bents such as the two column bents that support many bridge superstructures.The project includes the development of a test facility to test a variety ofconfigurations of L and T joints of large scale, followed by tests on a portion of a typicaltwo column bent from the Oak Street Bridge. The two column bent tests were sponsored3by the Ivlinistry of Transportation and Highways of BC (MOTH), and are reportedelsewhere (Seethaler, 1994 and Anderson et al., 1994). The tests of this investigation wereconducted on one “as-built” specimen and on one “retrofit” specimen, using half of theactual bent scaled to 0.45 of the original full size. The cap beam of the second specimenwas retrofitted using 6 Dywidag bars of diameter 5/8”. Each Dywidag bar was post-tensioned to 35 kips which is 80% of the ultimate strength of the bar. These bars weresupported at the end of the cap beam using 1.5” thick steel plates. The choice of specimenwas made to conform to corresponding tests on a 0.45 scale full bent from the samebridge, so that comparisons could be made between the half bent and full bent tests, inaddition to predictions of prototype performance.Testing consists of slow cyclic testing to simulate the reverse cyclic loading of anearthquake transverse to the longitudinal direction of the bridge. The loading rate,amplitude, and the number of cycles per sequence were kept as close as possible to the fullbent test loading pattern so that the comparison of results are meaningful.1.3 Test FacilityThe purpose of the test facility is to provide a means to apply jack loads fromvarious directions to a planar concrete structure, so that joint configurations of severaltypes could be loaded in their plane. The design objectives were developed to achieve afacility that would have maximum value for future investigations, withina limited budget(about $30,000).Overall design considerations were as follows:41. The busy structures testing laboratory has limited room for new facilities,therefore it is desirable to have a facility that is self equilibrating, i.e. does not depend onthe floor reactions to develop the applied load. This led to the decision to developarectangular frame that surrounds the specimen. Jack loads between specimen and frame donot impose external reactions. This permits the frame to be located anywhere in thelaboratory.2. In order to permit maximum future flexibility as to specimen size, and to permitpossible retrofits that may widen the specimen, a vertical, rather than horizontal,configuration was chosen. This permits fl.ill and equal access to both sides of frame andspecimen, and avoids limits on the specimen width.3. The maximum height of the frame above the floor of the laboratory is limited bythe overhead crane. In addition, the placement of specimens into the frame requires theoverhead crane.4. The height limit, and the desire to construct a frame as strong as possible withinthe budget, led to the choice of overall frame dimensions. Some preliminary analyses ofconcrete sections of the contemplated size led to load requirements for the frame. Thetestfacility design criteria and description are discussed in Chapter 2.51.4 Choice of Prototype StructureDuring the time the test frame was under development a number of actual bridgeswere considered as possible prototypes. As the time came to make a decision on aprototype, the British Columbia Ministry of Transportation and Highways (MOTH)decided to sponsor testing of Oak Street Bridge bents as part of a bridge retrofit programfor that structure. The MOTH program plan includes testing of a 0.45 scale model of bentS28 of the Oak Street Bridge (Anderson Ct al., 1994). The existence of the Oak Street fillbent tests then led to the decision to test half bents, i.e. half cap beam and one columnfrom the Oak St. bent, as part of this project. This achieves the ability to havea basis ofcomparison not only with analysis of the prototype, but with fill bent tests.The Oak street bridge was designed in 1954. It is 1.84 km long and supported on 83reinforced concrete piers. The bridge is 62’6” wide, and accommodates 4 traffic lanes and2 sidewalks. It consist of steel spans in the center and concrete spans in the North andSouth approaches.The approach spans consist of a series of four span continuous haunched concretegirders, supported on five concrete bents each with two columns. In the south approach,the 6.5” thick deck slab is supported on 5 reinforced concrete beams. These beams aresupported on concrete bents having varying heights. The superstructure is continuous overfive supports with expansion joints located at the end of the each four span section.Figures 1.1 and 1.2 show the elevation of the bridge and the general arrangement.6Figure 1.1 Photograph of the Oak St. Bridgec1‘1 ct CD CD c) CD B CDSOUTHAPPROACH(CONCRETE)TYPCONT.SPAN4060tI1iiIIt±iIIIHIIfiIIIHitIIINiCLAYSANDTILLTi’P.CONTINUOUS4—SPANSOUTHAPPROACH(STEEL)MAINSPAN(STEEL)NORTHAPPROACH(CONCRETE)1WCONT.SPAN:4060’j50120’205’300’204’jS2S1NOIHM::_EjIJIJ1I‘ii’iSAND’TILL8The bent S28 was chosen for the MOTH project and for this half bent project,asthis is a typical bent with an average height. The heights of the bents varies from about 20’to 60’. This is a first interior support of a continuous four span deck, therefore this supportwill attract the highest dead load.The cap beam of bent S28 has a cross section of 3’6”x5’ with two 8’6” long taperingcantilevers at the ends. Two 4’x4’ reinforced concrete rectangular columns of length 32.2’provide support for the superstructure at bent S28. See Figs. 1.3 to 1.5, Bent S28reinforcing details. The columns are supported on 14’6”x14’6”x3’ foundations which are on24 timber piles driven into sandy clay which is overlain on glacial till (Kennedy et al.,1992).In this thesis, the designation OSB 1, OSB2 etc is given to Oak St. Bridge fi.ill benttests done by others. OJ1, 0J2 refers to the half bent tests performed as part of thisinvestigation.9SflL JTCPER• oU-’—ELEVA11ON -09 LWFigure 1.3 Bent S28-reinforcing details of prototype (Elevation)CAPCD Cl) 00 1 CD -t C) CD 0 -t 0 0 CDC-) CD 0 0 0 CD CDC-) cr CD 0cIQ0 C,, CD CDPI(RCAPkP101 •111LSHAFt2•-, Crk?.)i.—itSEC11ON C-2 — I1 Uk.¶2 — 1I Uk. 22011 Uk. .31 — 011 Uk.J0(3 -d-ROWAI 2—i5Idk. Is2 — 011 Uk.. 11I LJiL.1— • Uk.10I I2 — ,11 Ik_ SI2 — 011 Uk. SbI..2—IllSEC11ON Al/T-P-0 -ROW AROW B— f11 Uk. 7— fit MA. S— fit IdA. S2 — fS MA. IS3 — 05 Uk. 14SEC11ON- i/T-1--0‘c1Fig. 1.5 Bent S28 reinforcing details prototype (Sections)121.5 SEISMIC DEFICIENCIES OF THE OAK STREETBRIDGE BENTSApart from loss of span failures, most of the seismic problems in this type ofconcrete bridge occur in the bridge bents. Poor detailing of reinforcement contributed tosevere damage of piers and joints of concrete bridge structures during the Loma Prietaearthquake (Mitchell et al., 1994). Specific deficiencies and retrofit schemes for Oak St.Bridge are discussed elsewhere (Kennedy et al., 1992). Some of the deficiencies in thebent which can be identified from the Oak street bridge drawings are:1. The shear capacity of the columns may be inadequate. These contain about 1%(Figure 1.5 ) longitudinal reinforcement but have only #3 ties at a spacing of 12” which isinadequate for these large columns. This insufficient shear reinforcement will result in thepossibility of a brittle shear failure in the column and it will not allow energy absorptionthrough flexural hinging which is the preferred method of seismic energy dissipation.Buckling of longitudinal bars and spalling of concrete is also common dueto widelyspaced tie reinforcement.2. The cap beam also contains about 1% longitudinal steel at Sections A and B.(Figure 1.5) The shear reinforcement in Section A consists of #4 closed stirrups at aspacing of 3 feet. Due to inadequate shear capacity in the cap beam, brittle shear failuremight occur in the cap beam due to lateral seismic loading.3. Anchorage of the cap beam longitudinal bottom bars in the joint region does notappear to be sufficient.134. Poor shear capacity in the joint region. The column tie reinforcement (# 3 bars@1’) has been continued but no extra ties are provided to carry the large shear force.5. The positive moment capacity of the cap beam at the face of the column is notsufficient (Kennedy et a!., 1992)As the shear capacity of the cap beam was found to be critically deficient, the asbuilt half bent specimen, OJ1, was tested for cap beam shear. The second specimen, 032,was retrofitted to improve the shear capacity of the cap beam, and then tested for capbeam shear, column shear and column flexure.1.6 CONCEPT OF JOINT PERFORMANCEReinforced concrete joint behaviour depends on the interaction of properties such asshear, bond and confinement. To understand the interaction of these properties itisimportant to first understand them acting independently, and this is still of interest toseveral investigators. In addition to the complex interaction of shear, bond, andconfinement, nonlinearities in concrete and the large variety in geometry and loaddistributions makes it extremely difficult to understand joint behaviour.Reinforced concrete frames typically have joints in which the connecting membersshould have sustained strength under deformation reversals into the inelastic range. Theconnecting members dissipate energy through reversal of deformation into the inelasticrange. In bridges, the development of plastic hinges in the columns is the preferredmethod of energy dissipation.14Different modes of failure possible in or near the joint region are:1. Beam hinging2. Colunm hinging3. Column crushing4. Reinforcement anchorage failure5. Joint shear failureThe failure of a joint and its connecting members will preferably absorb energythrough beam or column inelastic rotation. Failure of reinforcement baranchorage or thejoint region in shear will reduce the energy absorbing capacity and the load carryingcapacity of the system. Spalling of concrete in the joint region will reduce the compressiveload carrying capacity.The first experimental tests on beam column connections were doneby the PortlandCement Association around forty years ago and were published subsequentlyby Hansonand Conner (Hanson and Conner, 1967). Those results indicated that properly designedand detailed joints can resist moderate earthquakes without loss of strength. The amountand arrangement of the transverse steel in the joint and the method of anchoring beam barswere tested by Park and Paulay (Park and Paulay, 1973). Their results indicated thatabeam stub protruding beyond the far face of the column can be used to effectively anchorthe beam bars. Large variations in the axial load and the amount of transversereinforcement within the joint had little effect on the ultimate shear strength of the joint(Jirsa et al., 1975). Subsequent investigations were carried out to find the factorsinfluencing the shear capacity of the beam column connections. The shear strength of theconnection is primarily governed by the cross sectional area of the joint (Meinheit and15Jirsa, 198 1).The main objectives of most of the above experiments wereto improve theductility of the joint under reverse cyclic loading and to provide better anchorage forthebeam reinforcement in exterior connections.1.6.1 JOINT MECHANISMDue to seismic forces there will be moment reversals across the joint and thereforethe joint region is subjected to horizontal and vertical shear forces which are muchlargerthan the forces in adjacent beams and columns. Due to the above moments there willbe aforce gradient in the reinforcement with high bond stresses. If bond failure doesoccurthere will be excessive drift in the joint region, along with strength deterioration.During seismic loading the force transfer from the beam to the column through thejoint can be modeled by truss action, consisting of concrete struts and tension ties formedby the transverse reinforcement steel within the joint, which is activated by the bond stressand anchorage (Priestley and Paulay, 1991). This truss mechanism (Fig. 1.7) is relativelysoft, compared with the alternative direct compression strut (Fig. 1.6). The directcompression strut does not require reinforcement within the joint and therefore itdoes notrely on the bond characteristics. The strut, however, does have to be anchoredat the jointboundaries. This is a stiff mechanism and when concrete damages load will transferthrough the joint by the softer truss mechanism. In practice, the behaviour of thejointprobably falls somewhere between these two mechanisms.icFig. 1.6 Compression strutmechanismFig. 1.7 Truss mechanismCHAPTER 2TEST FRAME2.1 INTRODUCTIONPresent small scale-modeling techniques cannot adequately represent the complexforce transfer along the joint region of concrete structures or the deterioration of this forcetransfer as the load on the joint is cycled. Therefore to examine the behaviour of largescale concrete components (i.e. joints and regions close to the joint) of bridges under slowreverse cyclic loading, a self equilibrating steel frame was designed and constructed.The testing can be performed either vertically or horizontally. Although a horizontaltest setup might be easier to construct, a vertical frame is preferred as there is moreclearance between the specimen and the floor (for retrofit work etc.) and a better view ofthe specimen while testing. As the steel frame designed is self equilibrated it can beused asa horizontal frame if required.Two basic specimen configurations can be tested using this test setup. Those are,Interior beam colunm connection - T jointExterior beam column connection- L jointThe specimens can be tested either up side down or right way up dependingon therequirements. The specimen configuration and the loading arrangement can be chosento1718model the loading and deformation in a real structure in side sway due to lateralearthquake loading. The vertical and horizontal jacks at the top will provide pinnedconnections at the tip of the column. The testing is confined to two dimensions as theinteraction of the beams and columns are along the same frame.Fig. 2.1 Basic specimen configurationsWithin the specimen configurations shown above a wide range of specimen sizes canbe tested using this test setup. An elevation is shown in Fig. 2.3. The number, type (i.e. pinor roller) and the places of the boundary conditions at the bottom of the specimen can bechanged so that the required loading can be obtained in the beam stub. The vertical andthe lateral position of the load application on the column can be changed as described inSection 2.2. As two vertical jacks can be used at the column tip it is possible to obtain arequired moment and the axial load at the column tip and therefore it is not necessary tohave an inflection point at this location. The lateral jack can be used to apply the shear inthe column. It is also possible to apply a vertical load directly on the beam stub ifnecessary (i.e. dead load on the beam stub).192.2 CAPACITIES OF THE FRAMEThe design of the test setup had to be compatible with the existing laboratoryfacilities. Therefore the frame analysis provided for use of jacks similar to those used forthe beam element testing facility, which are of 1000 kN capacity. The steel frame wasdesigned to accommodate 2 vertical and 1 horizontal jacks of this capacity. Depending onthe requirements these jacks can act either in tension or compression.The force applied by the vertical jack on the column of the specimen reacts againstthe top girder of the test frame, while the force applied by the lateral jack on the columnreacts against either of the columns of the steel frame. These jacks can be repositioned at9-5/8” increments along the length of the girder and the column. The maximum values ofjack forces and the length on which those forces can be applied are shown in Fig. 2.2.Figs. 2.3 to 2.5 indicate sizes and details of steel frame, and Fig. 2.6 is a photograph of theframe mounted vertically in the UBC Structural Engineering Laboratory.The top girder can be repositioned between the two columns in three consecutivepositions at 2’ increments along the height of the column. Large steel sections were usedto construct the columns and the girder of the frame to provide adequate stiffness of theframe relative to the stiffness of the specimen. The bottom box girder is providedwith 1”holes at 3” spacing so that the boundary conditions of the specimen can be changed asrequired.20sno 625 695 625 62ia2 al bi b2MlDlisionsethnmAllowable Forces- al,bl,c, Max.Force 1000 KNMax Force 500 KN8400.11.1Fig. 2.2 Final magnitudes and ranges ofjack loads (inside of frame)ALLDIMENSIONSAREINMMROLlS024MMA32SUNLESSOUERWISESTATEDYIELDSTRENGTHOFSTEELHTOOMPABox,RDER:xft2O2(QUNDEREACHCoLW-*Jw;HcwT,4IYLLETL*SELDSitEs•70PTHREADSAREEXCLUDEDFROMSNEARPLANESOPTHEBOLTEDCONNECTIONSUNIVERSITYOFBCSTEELFRAMEELEVATION DRAWINGNITSFRIPREPAREDBYUSARAMRAWELADATETOH92xr*,raxcunw.,bliI I4129SCALEITOELEVATION13073S412.51II)T-1Ill11.PE4itkATrDN4ATHOOTOF01<OA’VE05/ID5IAFILLETWDLE_JillOll.I.’CiOo—llI_IITIII20MA01FF5IMANETHE006HOLESOFWBIOS201SYMMEII1ICALLYFROMTHEMIDHI.SCALEI02ONTHE0111SIDEFACEOFW6)07217ALLTHEHOLESARE025SECTIONAAAND75MMCCSYMMETRICALLYPLACEDFROMMIDIT3ALLSAlI_5.PHI’BAIMFI’L121.CICCB’UNIVERSITYOFBCSTEELFRAMESECTIONS DITAWINSNOSF02‘DEPOSEDBYUSARAMBAWELADATE30II32SCALEASSHOW’.2201’:::z———1-t--I-+tW610W610WBIDWBIDRiI—+t±-4.4--,-—4--I-—4-4--T+t-i--i-+1-—++1-—4+—444ft4+W310FLOORBEAMrJ a C) 0 -.5 $32IoW6)0—,-—..I1I59BO30013500LBa245,00005PLANSCALEl20i026a76II424iii1zzzzzzzII3130013243213NOTESF104--25SECTION88‘I’S3,1375125-1-L)328+t-I--f-I--I- ÷1-±r1 U’ 0 IW610W610BEAMCOLUMNTRUSSCOLUMN(TOP)0 CD 0 0 01)NOTES ALLWELDSAREFILiETWITHE480ELECII100ES2COLUMNTRUSSCONNECTIONAlCENTEROFCOLUMNISSIMILAR10lOP0USEso.ipITHICKENLFi.ATt3WT[I30MMWELTALL000,o000TilEW6IO041AILSFL610o2115EC5IUI-IS•15020MMMILLENDTRUSSIROTHSIDESIWi-2‘1,1WELTALLFILETI-IF4510*00UNIVERSITYOFBCSTEELFRAMEJOINTDETAILSDITAWINOl5003PTEPNREOBYUSAI8AMBAWELASI-Li-?CII52CHLE0COLUMNFLOORBEAMTRUSSFLOORBEAM24Fig 2.6 Photo of the steel frameCHAPTER 3TEST SPECIMENS3.1 INTRODUCTIONAs explained in the Chapter 1, bent S28 of the Oak St. Bridge at 0.45 scale wasselected so that the comparison with the MOTH fhll bent test can be done withoutcomplications of scaling. The existing material properties were used for the constructionof the specimens. The material properties are given in Section 3.5. Two half bentspecimens were made to the above specifications and one of those was retrofitted by post-tensioning the cap beam.3.2 PROPERTIES OF THE PROTOTYPE BENTThe cap beam of the prototype has a cross Section of 3’6” x 5’ with 4 - #11 bars atthe top and 13 - #11 bars at the bottom at section A. Figures 1.3 through 1.5 showprototype section details. In this region (Section A) there are #4 closed stirrups spaced at3’. The cross section of the supporting column is 4’ x 4’. The column contains 16 - #11bars and #3 ties spaced at 1,. The originally specified material strengths from the drawingswere compressive strength of concrete f’c = 20.7 MPa and the yield strength of steel fy =276 MPa. The material strengths indicated by the destructive test carried out by Klohn2526Crippen International were much higher. Concrete had a compressive strength of 41.4MPa and the column bars tested in S46 and N27 had yield strengths of 338 MPa and 400MPa respectively.3.3 PROPERTIES OF THE MOTH FULL BENT MODELThe MOTH model was at 0.45 scale and the cap beam had a cross section of 1’7” x2’3” with 4 - #5 bars at the top and 13 - #5 bars at the bottom. Thegauge 4 stirrups werespaced at 1’4”. The column had a cross section of 1’9.5° x 1’9.5” with 16 - #5 bars. Gauge9 ties in the column were spaced at 5 3/8”. Fig. 3.3 through 3.5 show the MOTH full bent.The material strengths obtained from the prototype testing were used for the experiment,as it is important to have correct material properties in order to identify the critical failuremodes. Therefore fc’=40 MPa and fy=345 MPa were used for the MOTH full bent model.The concrete cylinder strengths obtained from the first two MOTH specimens indicatedmuch higher average values of 47.6 and 51.1 MPa respectively.3.4 PROPERTIES OF THE HALF BENT MODELThe half bent should have a 11’ 8’ long cap beam with a cross section of 2’3” x 1’7”and a 9’ long column with a cross section of 1’9.5” x 1’9.5”. Due to the geometricallimitations of the frame the maximum cap beam length that can be accommodated is 1 1’.Therefore the length of the cap beam was reduced by 8” from the side oppositeto thecantilever. As described in the Introduction (Chapter 1) two specimens were built. Both27specimens have similar material properties, but the cap beam of the second specimen wasretrofitted by post tensioning. Geometry of specimen 1 and 2 are shown in the Figs. 3.1and 3.2. Bearing dimensions are given in Section 6.1. The reinforcing steel for bothspecimens was contributed by MOTH is therefore same as for the MOTH model.Concrete properties of the halfbent test are given in Table 3.1 and 3.2.Fig. 3.1 Specimen OJ128p21:5”p___:Fig. 3.2 Specimen 0J2295T1. ABOJTf.PEACES• 1—4 STUPS4 — 4 Go. !1TRMJPS.- L3.5/t__• rriL1 tZL_____/1’E E!1!tL__•$ 1,1—,£S./ ATuRN€D9qUS3 r-0 14.-___- (3 o -a 14.TO LAPIk105I I J.--VGOWWNLGC.ALI.Y 70 cGeUTE -ELEVA11ONFig. 4.3 MOTH model elevationc!QC H C CDC -f -f 0 C,) CD CDH 0 C,) -f CD CD00 0 (D (t C) I-. 0IIIIIIII—onIJLIP(mIIIILAG.%J.1.J—C(‘)323.5 CONSTRUCTION OF THE SPECIMEN3.5.1 FORM WORKAs testing was planned to carry out upside down it was decidedto construct thespecimens upside down, i.e. beam laying flat on the floor. Half inch diameter tierodswhich can carry 4500 pounds and quarter inch snap ties which cancarry 2250 pounds intension were used to support the liquid concrete pressure. One inch thick plywoodwasused so that the number of ties required for the lateral load supporting scheme couldbeminimized. Fig. 3.6 is a photograph of the form prior to placing concrete.33Fig. 3.6 A photograph of the form work?•.•.1I343.5.2. REINFORCING STEELThe reinforcing cages for the beam and the column were assembled outside of theform work and all the strain gauges were installed before making the cages. First the twobearing plates were assembled in the form work, then the beam cage was placed, followedby the column cage. Figure 3.7 is a picture of the reinforcement in the form work. Toobtain the concrete cover plastic chairs were attached to the reinforcement. The yieldstrength of the reinforcing main bars and stirrups were 345 MPa.The cap beam of the second specimen was post-tensioned using 6 Dywidag bars ofdiameter 5/8”. Each Dywidag bar was tensioned to 35 kips which is 0. 8fu. The resultantpost tensioning force before relaxation of the bars is 210 kips acting 12.5” below the topface of the cap beam. This provides the same prestress as the MOTH full bent test.35Fig 3.7 A photograph ofthe steel cages363.5.3. CONCRETEThe ready mixed concrete was obtained from a local supplier. Theconcrete wasordered 5 MPa lower than the required strength because thesuppliers tend to supplyhigher strength concrete. Unfortunately the strength of concretereceived was much lowerthan the required strength. The height and the diameter of concretecylinders tested were12” and 6” respectively. A total of twelve cylinders were tested forthe first specimen, outof which a set of six were air cured and six were moist cured.The two fiat sides of all thecylinders were grinded before testing. Three cylinders ofeach set were tested underuniaxial compression after 28 days. The rest weretested after 2 months (while testing thespecimen). The cylinders were not dried before testing.Table 3.1 Concrete properties of OJ1Strength Slump (in) Aggregate Air(MPa) size (in)Content(%)Requested 35 5 0.5 0Delivered 4.5 0.5 2.5Average 28 day 26.0(D) — ——26.0(W)Average at 31.5(D) — ——Testing(2 31.0(w)months)37Total of ten cylinders were tested for the second specimen. Out of whicha set offour were air cured and six were moist cured. Two of air cured and three of moistcuredcylinders were tested under uniaxial compression after 28 days. The rest weretested after2 months (while testing the specimen). The cylinders were not dried before testing.Table 3.2 Concrete properties of 0J2Strength Slump (in) Aggregate Air(MPa) Size(in) Content(%)Requested 35 5 0.5 0Delivered 5 0.5 2Average28 day 32.8(D) — — —33.25(W)Average at Testing 30.4(D) — — —(2 months) 40.5(W)D - Air curedW - Moist curedThe cylinders were crushed using the Baldwin after 28 days and when testingof thespecimen. The 28 day compressive strengths were much lower than the expectedvalues.As a result of the difficulty of proper vibration of the upside down curveregion of thespecimen there were a couple of small honeycombs in that region. Fortunatelymost werein the cantilever side of the beam of both specimens except one small honeycombon the38other side of the beam of specimen0J2. The cantileverside of the beam is not of directconcern in these tests. Bothspecimens were white washedso that the crack patterns couldbe seen better.Fig. 3.8 Photograph showingpouring ofthe concrete39Fig. 3.9 Post-tensioning ofbars40Fig. 3.10 Installing thespecimen in the frameFig. 3.11 Specimen andthe frameCHAPTER 4INSTRUMENTATION AND DATAACQUISITION SYSTEMS4.1 INTRODUCTIONThe equipment used to load the specimen andto store the data consisted of thefollowing;OPTILOG for data acquisitionMTS controller for the application of the loads2 hydraulic actuators for the first specimen and 3 actuators forthe second specimen2 IBM Personal Computers20 strain gauges per specimen3 LVDT displacement transducers1 Load cell1 Pressure Transducer for the first specimen and 2 for the secondspecimenThe loading function for the lateral loading jack at the columntip was generatedusing a MTS 458. 1OCIO.20C Microconsole. The loading for thelateral jack was underdisplacement control. The hydraulic pressure of the other jacks wascontrolled manually inrelation to the lateral loading jack so that the required loading functionwas achieved. The4142jacks used for the application of the column reaction vertically (J2) and horizontally (Ji)had a capacity of 200 kips and 100 kips respectively.The measuring devices used were strain gauges, linear variable differentialtransformers (LVDT displacement transducers), and a load cell attached to the lateralloading MTS jack. The strain gauges type was FLA-5-1 1, the resistance and the gaugelength were 120 ohm and 5 mm respectively. Fig 4.1 shows an individual strain gaugemounted on a reinforcing bar.43Fig. 4.1 Photograph ofa strain gauge in a bar44For data acquisition the OPTILOG systemwas used with the OPUS 200 software.(OPtim Users’ Software) OPUS 200 is a BASICcomputer program which controls thecollection of voltages from several channels andconverts them to loads, displacements andstrains which are stored, printed and plotted.26 different measurements were recordedusing the OPTILOG 120 data acquisitionsystem for the specimen OJ1. Those consist of 20strain gauges, 4 LVDTs ,1 Load Celland 1 pressure transducer. For the specimen0J2 there was an additional pressuretransducer for the third jack. The data acquisition systemscanned the devices at a constanttime interval of 2 seconds. Fig. 4.2 shows the data acquisitionsystem.Fig. 4.2 Photo of the data acquisitionsystem454.2 INSTRUMENT LOCATIONS4.2.1 STRAIN GAUGE LOCATIONSTwenty strain gauges were attached to the beam and column main bars and ties inthe joint region. See Fig.4.3 and 4.4. These strain gauge locations coincide with some ofthe strain gauge locations of the MOTH full bent test. This was doneso that the bent andthe joint test results can be compared with each other. Table 4.1 indicates the strain gaugedesignations and correspondence with the full bent test. Table 4.2 gives the strain gaugelocations in the half bent specimen.At the strain gauges locations the bars were machined and smoothed to provideaflat surface for mounting. The smoothed surface was then cleaned, the strain gauge andthe terminal strips mounted with glue. Wires were then soldered. After applying theprotection coating the strain gauges were covered with putty and aluminum paper forprotection. The strain gauges were then checked to ensure that the connections wereworking before assembling the reinforcing cages. The cables leading from the gauges weretaken along the bars so that damage to these while pouring the concrete wouldbeminimum.ciriôC)_C/)CI3CCC.:::::L’JcM-tL’3-c)i’.)-IIf) C1 CD-.‘‘-oc4cccM-‘C..‘DGoO4‘CD ,-. CDT1T1C1C):.CD . CD .*47Table 4.2 Strain gauge locations (X-Y Coordinates with the center line of thecolumn top as the origin.)Strain Gauge X (inches) Y (inches)Cli 8 7C13 8 31C14 8 37COl -8 7C03 -8 31C04 -8 37CT2 0 14CT3 0 23CT4 0 29BS1 12 16BS2 19 16BS3 34 16BT1 -13 2BT3 0 2BT4 6 2BT5 14 2BT6 22 2BB1 6 24BB2 14 24BB3 21 24(J,) c,) CD 0 0 0 049Fig. 4.4 Strain gauge locations (Plan). Elevation in Fig. LVDT LOCATIONSThree LVDTs were used to measure different displacements. First LVDTwasinstalled 9’ from the bottom of the specimen on the center line of the columnparallel to thelateral loading plane to find the column tip deflections in the lateral loadingdirection.Although there is a built in LVDT in the lateral loading MTS jack the pin of thatjack was50loose in the clevis of the loading plate. Therefore when the loading direction is reversed itwas suspected that the load displacement relationship would not be very accurate.The second LVDT was located 13.5” from the bottom of the specimen in the centerline of the column. The third LVDT was located 3’ 10.75” horizontally away from thesecond LVDT in the beam stub. See Fig. 4.5 and 4.6. The latter two LVDTs can be usedto measure the crack widths in the beam stub, and the horizontal displacements in the jointand the beam stub.U,Fig. 4.5 LVDT locations51Fig. 4.6 Photo of LVDT locationsCHAPTER 5TESTING PROCEDURE5.1 BOUNDARY CONDITIONSIn the actual bridge the dead loads from the deck, to the bent are applied at the fivegirder positions. The lateral seismic load acts on the center of gravity of the deck which is5’ above the top of the bent. The lateral seismic load was assumed to be shared equallybetween the two, first interior bearings in the MOTH full bent test.Two supports (bearings) were used for the half bent specimen. The “first interior”support is a pin to take the total lateral load, and the “middle” support is a roller so that itwill share the vertical reaction due to the lateral seismic load with the pin support. Thesebearings consist of 2 steel plates of 2” and 1.5” thick and a 3/8” elastomeric pad betweenthe plates. The bearing locations are shown in Figs. 5.1 and 5.2. The bearing arrangementis shown in the Fig. 5.3. The bolts attaching the top bearing plate to the bottom plate atthe pin support is provided with 1/8” play so that the top bearing plate can rock on theelastomeric pad. At the roller support 1.5” slotted holes were drilled to allow for thehorizontal movement of the specimen on the bearing pad. Figures 5.4 and 5.5 arephotographs of pin bearing and, the vertical and horizontal jack connection detail.5253Q vertical jack11 Qhorizontal jackbH2V 36 15.5 15 22.5 164Q pin bearingroller bearingFig. 5.1 Specimen OJ1 bearing locations540CL vercaI jackhorizontal jackQthirdiFig. 5.2 Specimen 0J2 bearing locations558- #5 bars enedded in the specimenconcrete specimenI I II II12’125<3Ir elastomeric padII5’• 30’-.--_top bearing platebottom bearing platesteel frame5-FRONT ELEVATIONPLANFig. 5.3 Bearing arrangement56Fig. 5.4 Photograph of the pinbearing57Fig. 5.5 Horizontal and vertical jack connection.585.2 LOADING SEQUENCEThe shape of the load deflection curve and the energy dissipation capabilitiesdepend on the loading path and history of cycles. Therefore it is importantto apply similarloading patterns if comparison of results of different tests are expected to be carriedout.Specimens subjected to large load reversals at the beginning of the load history showasignificant deterioration of energy absorbing capacity, i.e. initial large displacementspromotes deterioration of energy absorbing capabilities (Kawashima et al., 1988).Forspecimens which fail in shear, the number of inelastic loading cycles has a more significanteffect than for flexural specimens. The number of loading cycles is important in flexuralspecimens if the ultimate failure mode is associated with the tension failure or bondfailureof main bars (Koyama et al., 1988).5.3 LOADING ON THE FULL BENT MODELIn the Oak St. Bridge, dead load from the deck acts at the five bearing positions onthe cap beam of the bent. The lateral load is assumed to act on the center of gravity of thedeck which is 5’ above the center line of the cap beam. Fig. 5.6 shows the forces andreactions due to dead and lateral loads acting on the MOTH full bent model. Section x-x istaken to the right of mid span of the cap beam. The lateral load is denoted P and isanalogous to the seismic base shear. As the half bent specimens were tested upsidedown,the dead loads have been taken as 42.5 kips, reflecting the total dead load ofthe specimenincluding the column.59DEAD LOAD EFFECTALL LOADS ARE INKIPSP = LATERAL LOADLATERAL LOAD EFFECTFig 5.6 Dead and lateral loads on full bent test5.4 LOADING ON HALF BENT SPECIMEN OJ1Specimen OJ1 was tested using 2 jacks at the tip of the column. The twojacksused for the application of the column reaction vertically (J2) and horizontally (J1) had acapacity of 200 kips and 100 kips respectively. The 200 kip jack is double actingwith 12”stroke, whilst the 100 kip jack is double acting with 6” stroke. The 100 kip jackwas usedto apply slow reverse cyclic loading laterally at the column top under displacement42.5 42.5 42.5 42.5 42.5V 4VXIVV5”__67.5” 67.5”1O6.2564 5”4.0106.2500.5P+O.816PO.816P60control, while the load of the vertical 200 kip jack was controlled proportionately to the100 kip jack. The bending moment at the cap beam end (joint 10), correspondingto midspan in the full bent tests, has been neglected for both specimens OJ1 and 032 to simplifythe loading arrangement, i.e. to reduce the number of jacks. Fig. 5.7 shows the loadapplication on specimen OJ1. The line diagram shows member centerline dimensions. Thefirst interior support, the pin, will absorb the total lateral load due to the earthquake andthe vertical load due to the earthquake will be carried by the pin and the roller, such thatthe shear force of the cap beam at the roller is in the required region.R1=2.07J1 -0.35J2R2 = 2.0711 - 1.35 J2R3 =J1APPLIED LOADINGJ20)JOINT 6- PINJOINT 9- ROLLERR2 RIMODEL OJIFig 5.7 Loading OJ161From Fig. 5.6, shear at section xx (joint 7) due to dead load is -21.25 kips. Shearatxx due to live load is -0.516P kips. Where P is the lateral load acting on the MOTHfillbent. Shear is taken as positive using the usual beam convention. The resulting total shearV at section xx, when P is positive acting to the right is,V=-21.25-0.516P (1)For the half bent specimen the corresponding shear in the cap beam based on thegeometry and support conditions of the specimen OJ1 (Fig. 5.7) is,V = 2.07 (J1) - 0.35 (J2) (2)Jacks 31 and J2 were then controlled to obtain the variation of V. The sequence,maximum lateral displacement and the maximum lateral load applied at the columntip aregiven in Table 5.1. The jack J2 was controlled in relation to J1 accordingto therelationship in equation 3,J2 = 2.17 (J1) + 47.23 (3)The corresponding J2 jack loads and the sequences are given in Table Cl ofAppendix- C.The Fig. 5.8 and 5.9 show the loading curves of 31, J2 and the variation of shearandbending moment at section xx of the specimen 031 cap beam. The axial load actingin thecap beam at this section is zero. The Fig. 5.10 shows the variation of shear at section xx in62the half bent test and the MOTH fl.ill bent (OSB1) with the loading sequence. The forceresultants for the complete specimen OJ1 and OSB1 at the maximum loading condition aregiven in the Appendix B (Figs. B1-B8).Table 5.1 Jack Ji displacement and mm/max loadSequence Dispi. Ji (in) min(kips) max(kips)A 0.1 23.0 26.8B 0.2 12.1 32.0C 0.25 11.6 33.2D 0.3 12.2 36.2E 0.5 10.2 41.2F 0.6 7.3 43.4G 0.7 3.1 45.6H 1.00 -2.1 51.0I 1.25 -7.1 51.4J 1.5 -13.9 47.2K,L,O 2 -9.1 49.5P 2.5 -15.6 41.6Positive acting to right (see Fig. 5.7)Initial load of the lateral jack was Ji =22.5 kips acting to the right hand side (Fig.5.7) to obtain the dead load shear at the roller bearing of the cap beam. At this load lateral63column tip deflection was 1.4”. This was the zero position for Ji displacement in Table5.1.1601401201008060940200-20JACK Ji, J2 VS SEQUENCEA AIiIIii iii iiF Fii Il ji jijij,Ij jjj (jjj jjII/S\/\lj/j\I I,A i i i i A A iA\/I./ IfIIIII II\iIi\/\I\ , , I’ II 1/II,I, II.1/IIIF II III IIi 1:—-- A A AJ\J\J\AA/i\//\vyyyyA B C DEF GSEQUENCEH I J PFig. 5.8 Applied jack loads specimen OJ16400.1CE0-SICoShear and Moment Variation Vs Jack LoadsFig. 5.9 Shear/Moment variation of OJ1 cap beam section xx with jack loads6050403020100-10-20-30-40200150100500-50-100Bea, LMment---—E am Shearz--150Ji (Kips)0J2 (Kips)4-10 0 10 20 30 405026 47 69 91 112 134 156Cl)aLUCl)1/\/A\II(t I’OSB1A’VVVA’VVVA B C D E F G H IJ pSEQUENCEFig. 5.10 Cap beam shear variation of specimen OJ1 and OSB 165Fourteen sequences of sinusoidal lateral load cycles were applied during the first testbut due to malfunction of the data acquisition system data for 2 of the sequences were notrecorded. Each sequence consisted of two cycles. The period of the cycles were 10minutes and the scan rate was 2 seconds. Due to the restriction of the stroke of the lateraljack maximum displacement applied was 2.5”.Upon completion of this test, the column remained undamaged. It was thereforedecided to carry out a column test on the same specimen. A third support and a tie downon the cantilever side of the cap beam was provided. The two sides of the cap beam endswere supported against the steel frame. Three sequences of 1 “,2”,2. 5” displacementsat thecolumn tip was applied. The stroke to the north (puffing) was only 2.5”, therefore it wasdecided to apply a push to the south with the maximum available stroke of 3.5”.665.5 LOADING ON HALF BENT SPECIMEN OJ2The specimen OSB2 was retrofitted to improve the cap beam shear and momentcapacity. This retrofit scheme consist of applying 210 kips of post tensioning force to theexisting cap beam through a cored hole. The cap beam of the specimen 0J2 was externallypost-tensioned by using 1.5” thick end plates and six 5/8” Dywidag bars each carrying 35kips. These forces were applied to specimen 0J2 such that it will duplicate the posttensioning forces applied for the specimen OSB2.In specimen OJ1 the major concern was cap beam shear. Therefore during testingof specimen 1 correct shear in the cap beam was applied using two jacks at the column tip.But in the retrofitted specimen column shear is also of major concern. Therefore thecorrect column reactions were applied at the tip of the column using Ji and 32, and a thirdjack (J3) was controlled to obtain the correct shear in the cap beam. Loadsin both verticaljacks were allowed to change in proportion with the lateral jack. The lateral jack was onreversed cyclic loading under displacement control. The third jack 33 was 3’ away from thejoint 5 on the cantilever side.(Fig.5. 11)67—J2- JOINT6-PINJOINT 9-ROLLER— 11U,--________12 43 4 67 8 10R31R2X¶R121” 36”15.5”i6” 15” 22.5 16”MODEL0J2Ri = 2.1J1 + 0.8J3 -0.4J2R2 = 2.131 +1.8J3 -1.4J2R3 =31Fig. 5.11 Loading 0J2The two jacks at the column tip Ji and J2 were varied in relation to P (lateral loadon the MOTH full bent) to obtain similar column loading to the Full bent test,Ji = P/2+4 (4)J2 = 0.8 16 (P) + 106.25 (5)J3=42.5-0.24P (6)The third jack J3 was varied such that the cap beam shear at section xx is (Section5.4),68V = -21.25-O.516P (7)Jacks 31, J2 and J3 were controlled to obtain the variation of shear both in thecolumn and the cap beam. The sequence, maximum lateral column tip displacementandthe maximum lateral load (Ji) applied at the column tip are given in the Table5.2. Theother two jacks J2 and J3 were controlled in relation to Ji. The corresponding J2 and 33jack loads are given in Table C.2 of Appendix C. The Figs. 5.12, 5.13 show the loadingcurves of the three jacks and the variation of shear and the moment at beamsection 7 andcolumn section 11 (Fig.5. 11) of the specimen 0J2. The axial load at section 7 ofthe capbeam is zero. The Fig. 5.14 and 5.15 show the comparison of the variation of the shear of032 and OSB2 at the section 7 of the cap beam and the column respectively. Theforceresultants for the complete specimen 0J2 and OSB2 at the maximum loading condition aregiven in the Appendix B (Figs. B9-B16).The initial load of Ji for the second test was J1=4 kips acting to the right handsideto account for the dead load reaction at the column tip. The other two jacks were variedaccording to equations (5) and (6). Thus at J14 kips, 32=106.25 kips, and 33=42.5 kips.This simulates the dead load condition.69Table 5.2 Jack 31 displacement and mm/max loadSequence Displ. Ji (in) miii (kips) max (kips)A 0.1 -1.1 6.3B 0.2 -5.8 8.7C 0.4 -12.5 19.8D 0.6 -19.4 29.3E 0.75 -24.5 35.8F 1.00 -32.8 43.4G 1.25 -38 49.2H 1.50 -40.2 51.3I 1.75 -41 50.5J 2.00 -41 50.2K 2.50 -42.9 60.6L 3.00 -42.3 56.4M 4.00 -45.6 30.8Positive acting to right (see Fig. 5.11)Thirteen sequences of load cycles were applied. Due to the malfunction of thecolumn tip LVDT 3 sequences had to be repeated. The number of cycles persequence,period and the scan rate were similar to the specimen OJ1. In the sequence3 (2” lateraldisplacement) for pulling the stroke was not enough. Therefore a 0.5” steel platewasinserted underneath the roller to get an extra 1” displacement at the column tip. After thatanother two sequences of 2.5” and 3” were applied. Then the steel plate was removed and70a push of 4” was applied. The last three sequences were recorded in the Table 5.2 forcompleteness. But those were not taken in to account for subsequent calculationsbecausethey look unreliable.JACK Ji, J2,J3 VS SEQUENCE‘ 4 4 IA A AA A A A1 P H ii H H H H•‘IH Il 1.J 2i I.— ,. /l i IjI IiI III I ‘I IIIIIl II— \, ‘4 ‘, I‘III IIII IIil II If liii‘‘I It I I/ II / I II‘I1 II II///II II II IIJ 31 /, I,/,III II II II II:zz;A/V\NN\A/V‘• 4’,Cl)00-j200150100500-50A B C 0EF G H I JSEQUENCEFig. 5.12 Applied jack loads specimen 032715004003002001000-100-200-300-400Ji (Kips)Shear and Monent Varialion Vs .bck Loads=E0-CCi)-40 -20 0 20 4060Fig. 5.13 Shear /Moment variation at x-x of 0J2 with jack loadsCAPBEAM SHEAR VS SEQUENCEci)0UICl)806040200-20-40OSB2LI0J2.\(I II I\III \ I IIII illII I\Afl\WivrlII III‘II.Ii‘‘I I‘IA B C D E F G HSEQUENCEJFig. 5.14 Cap beam shear variation of specimen 0J2 and OSB272COLUMN SHEAR VS SEQUENCEOSB20J2I• I\i\ I’ II I I i\\iiAi1iV\u1WMW.npyII1IIIIyI1 “1Ii IIV V ‘I6040-60A B C D E F GH I JSEQUENCEFig. 5.15 Column shear variation of specimen 0J2 and OSB2CHAPTER 6EXPERIMENTAL OBSERVATIONS6.1 SPECIMEN OJ16.1.1 OBSERVED BEHAVIOURFlexural cracks in the column (south side) appeared when pulling to the north insequence A at0.10displacement. These cracks extended in the subsequent cycles. Insequence E at 0.5” displacement (puffing) and a lateral load (Ji) of 41.2 kips first flexuralcracks at the top side (bottom on the upside down specimen) of the cap beam appeared.These cracks extended in the subsequent sequences. Fig. 6.2 shows the cracks of sequenceF at 0.6” lateral column tip displacement. At sequence F the lateral load Ji appliedwas43.4 kips and the cap beam shear at section xx (Fig. 5.7) was 40.3 kips. The peak lateralload was obtained in sequence H at 1” column top displacement. At this sequence thewidth of the cap beam shear crack was about 0.6mm. Up to sequence J (i.e. 1.5” columntip deflection) when loading north (pulling) the cap beam top shear crack openedupwithout forming other cracks. After sequence H the strength and the stiffness of thespecimen started degrading. This can be clearly seen from the lateral load displacementhysteresis loops of the column tip (Fig. 6.1). The initial position of the lateral loadingjackfor this test was 1.4”. In sequence 0 at 2” lateral column tip deflection (Fig. 6.3)a majorshear crack started spreading in the joint region when pushing South. At this sequence thelateral load applied was 49.5 kips and the cap beam shear at section xx was 48.3 kips. The7374width of the cap beam top shear crack was about 8 mm in this sequence. The lateral loaddropped to 41.6 kips in sequence P at a displacement of 2.5”(Fig. 6.4).As explained in the section 5.4 (by using an extra support and a tie down on thecantilever side of the cap beam), a separate column test was carried out with four loadsequences. The load displacement curve of this test is shown in the Fig. 6.5 and thecracking at the last sequence is shown in the Fig. 6.6. In these sequences there was nomajor cracking in the column apart from the extension of the cracks that were alreadyformed. Hysteresis loops of the column test clearly shows the yielding of column steel inboth directions (Fig. 6.5).OAK ST. JOINT SPECIMEN175302010-10-20/;//-//--—-3000 -2000 -10000 1000 2000 3000 4000COLUMN TIP DISPLACEMENT(1/1000) INFig 6.1 OJ1 Load displacementat the column tip\Fig. 6.2 Photograph of crackpatterns at sequence F76OA ITlO.IT Tilt‘l tI3.IptcIpNIdlUEItCtPFig. 6.3 Photograph of crack patterns at sequence0I---IJFig. 6.4 Photograph of crack patterns at sequence PC.j)FSPECIvffiN-1 (COLUMN TEST)COLUMN DISPLACEMENT (1/1000)INCHFig 6.5 Load displacementat the column tip (Colunm Test)776040200-20-40—;;--3000 -2000 -10000 1000 2000 3000 4000Fig. 6.6 Photograph of crackpatterns at Push Over786.1.2 SECTIONAL ANALYSISThe maximum sectional forces and sectionalcapacities of specimen OJ1 arecompared in this section at locations where plastic hinges orshear failure were anticipated.Node locations and load application are shown in Fig. 5.7.The applied cap beam momentand shear force variations were given in Fig. 5.9.Appendix B describes the forceresultants of the whole specimen at the maximum load.Table 6.1 OJ1 Maximum demand (critical sectionalforces) for pullingMEMBER NODE AXIAL SHEARMOMENTFORCE (kips) FORCE (kips) (kip if)10 5 159.0 51.4385.5(column) 11 -159.0 -51.40.06 6 0.0 -49.7-180.17 0.0 49.7 155.37 7 0.0-49.7 -155.3(sectionx-x) 8 0.0 49.7 95.0Table 6.2 Maximum demand (critical sectional forces) for pushingMEMBER NODE AXIAL SHEARMOMENTFORCE (kips) FORCE (kips) (kip if)10 5 12.5 -16.0-120.0(column) 11 -12.5 16.00.06 6 0.0 42.2156.17 0.0 -42.2 -127.57 7 0.0 42.2127.5(section x-x) 8 0.0 -42.2-77.379The capacities at joint 7 (Fig. 5.7)were obtained using Program Response. ProgramResponse was developed at the Universityof Toronto (Collins et al., 1991) to calculateconcrete section capacities. The input consists of thesectional properties and the loading.The loading can be given as the axial load and themoment at zero shear and the variationof theses two parameters with the shear. Usingthe applied loads at joint 7 of specimenOJ1, input values were obtained as shown in Table6.3. Where, N is axial load, M ismoment, and V is shear.Table 6.3 Input loading OJ1 joint 7Specimen OJ1Joint 7Axial (kips)@V0 1.1Moment (kip ft)@V=0 2.48dN/dV 0dM/dV - 3.07The above input can be used to find out the influenceof moment, axial load and theshear force on the section under consideration. Themaximum shear obtained and thecorresponding moment and the axial load at the joint 7 are shownin Table 6.4.Table 6.4 Out put capacities OJ1 joint 7Specimen OJ1Joint_7Axial (kips) 1.1Shear (kips) 61.1Moment (kip fi) 190.180These values were compared with the values obtained from the testing. The appliedmaximum forces for specimen OJ1 at joint 7 (Fig. 5.7) were 49.7 kips shear and 155.3kipft moment (Table 6.1) The values predicted by the Program Response were 61.1 kipsshear and 190.1 kipft moment (Table 6.4). Response predicted shear capacities were about20% higher than the peak applied shear force, based on analysis only at joint STRAIN GAUGE READINGSThe reinforcing bar yield stress is 345 MPa. Therefore yield strain should be around0.00 1750 (1750 Micro strain). Surprisingly most of the beam stirrup strain gauges ofspecimen 1 close to the shear crack and column tie strain gauges of specimen 2 close tothe flexural crack indicated very low strain values, (i.e. around 50 micro strain) in bothtests. When there are cracks propagating across reinforcing bars then those bars areexpected to carry most of the load if not all. Therefore the stirrup and tie strain gaugevalues are questionable. Bottom bar strain gauge BB3-12 of specimen 1 (Fig. 6.7) isclearly yielding in the last couple of cycles when pulling North. The other strain gauges ofbeam main bars also carried very high strains in the last couple of cycles i.e. BB2-1 1, BT5-5, BT6-6.816050o4030R20-100-10-20SPECIMEN 1 BEAM BOTTOM STRAIN GAUGE (BB3-12)c\\...-2000 -1500 -1000 -500 0 500 1000 1500MICRO STAlINFig 6.7 Strain gauge BB3826.2 SPECIMEN 0J26.2.1 OBSERVED BEHAVIOURFlexural cracks in the column started in the sequence D (Fig. 6.9) at 0.6” lateraldeflection of the column tip around 29 kips lateral load. At a lateral column tipdisplacement of 1” in the sequence F more flexural cracks in the column appeared. At thisstage spacing of cracks in the column in both directions were around 6”. This was veryclose to the spacing of the ties in the column which is 5 3/8°. Flexural cracks in thecapbeam appeared in sequence G at 1.25” lateral deflection of the column tip around 50 kipslateral load. At sequence H diagonal shear cracks in the column startedto develop. Thiswas at 1.5” lateral deflection of the column tip. As the test was started with an initial offsetso that the correct dead load effects can be imposed, there was only 2” stroke in the Northdirection pulling. Therefore it was decided to insert a 0.5” steel plate at the roller bearingalong with the neoprene pad to give an extra 1” of northward stroketo the lateral columntip jack. In sequence L (Fig. 6.10) at a lateral column tip deflection of 3” and a lateral loadof 56 kips, the column flexural cracks just above the beam curve opened widely. Atsequence M when the column tip deflection was 4” the column concrete startedspalling.(Fig. 6.12).836040o20-20-40-60OAK ST. JOINT SPECIMEN2COLUMN TIP DISPLACEMENT (1/1000)IN0.5” PLATE UNDER ROLLER4/1:_-4000 -3000 -2000-1000 0 1000 2000 30004000Fig. 6.8 OJ2 Loaddisplacement at the column tiprOISDtce9‘I2‘ 2tOUUCLccUeIYSP’-06 I6.9 1 .tograph of crackpatterns at sequence D84Fig. 6.10 Photographof crack patterns at sequence LFig. 6.11 Photograph ofcrack patterns at Push Over85Fig, 6.12 Photograph ofcrack patterns at Push over6.2.2 SECTIONALANALYSISThe maximumsectional forces (the last3 sequences were ignoredbecause theyappear to be unreliable)and sectional capacitiesof specimen 0J2 are comparedin thissection similar to specimenOJ1 at locations where plastichinges or shear failure wereanticipated. Node locationsand load application areshown in Fig. 5.11. The appliedcapbeam and column forcevariations were given in Fig.5.13. Appendix Bdescribes the forceresultants of the wholespecimen at the maximumload.86Table 6.5 0J2 Maximum demand (critical sectional forces) for pullingMEMBER NODE AXIAL FORCE SHEAR FORCE MOMENT_____________(kips) (kips) (kipft)11 11 180.5 50.5 378.8(column) 12 -180.5 -50.5 0.06 6 0.0 -67.4 -244.37 0.0 67.4 210.67 7 0.0 -67.4 -210.6(sectionx-x) 8 0.0 67.4 126.4Table 6.6 0J2 Maximum demand (critical sectional forces) for pushingMEMBER NODE AXIAL FORCE SHEAR FORCE MOMENT(kips) (kips) (kipft)11 11 26.3 -45.0 -337.5(column) 12 -26.3 45.0 0.06 6 0.0 32.5 119.87 0.0 -32.5 -97.77 7 0.0 32.5 97.7(section x-x) 8 0.0 -32.5 -59.2As explained in the section 6.1.2 of specimen OJ1 the input values at two criticalsections of specimen OJ2 were calculated to be used in the Program Response (Collins etal.,1991). N is axial load, M is moment, and V is shear. The cap beam positivereinforcement had numerous cutoff points. Table 6.8 shows only the results for joint 7 and11.87Table 6.7 Input loading 0J2 joints 7 and 11Specimen 0J2 Specimen 0J2Joint 7 joint 11Axial (kips)@V0 -210 -100Moment (kip ft)@V0 -3.09 0dN/dV 0 1.6dMJdV 3.74 5.42The calculated values of the maximum shear at joints 7 and 11 andthecorresponding moment and the axial load values are shown in the Table 6.8.Table 6.8 Output capacities 032 joints 7 and 11Specimen 0J2 Specimen 0J2Joint 7 Joint 11Axial (kips) -210 38.5Shear (kips) 82.2 38.5Moment (kip ft) 304.4 208.4Maximum push applied on specimen 032 at joint 11 (Fig.5. 11) were 45kips shearand 337.5 kip ft moment (table 6.6) The values predicted by the programResponse were38.5 kips shear at a Moment of 208.4 kip ft. The increase in the cap beamshear of thespecimen 0J2 over 031 was around 35% without any significant cracking in thecap beam.887.2.3 STRAIN GAUGE READINGSIn the specimen 0J2 column outside strain gauge C04-29 (Fig. 6.13) yields whenpulling North with 45 kips. The inside strain gauge C13-23 (Fig. 6.14) yields when pushingsouth in the last couple of cycles. These high strain values clarifies the very high bendingmoments expected at specimen cross sections along these strain gauges. Strain gaugesBB2-1 1 and BB3-12 of specimen 0J2 carries much lower strains than BB2-1 1 and BB3-12 of the specimen OJ1. This was due to the prestressing force applied to the cap beam ofspecimen 0J2.SPECIMEN 2 COLUMN OUTSIDE STRAIN GAUGE (C04-29)C___ ___ ___ ___ ___ ___ ___ ___ ___6040200-20-40-60-4000 -2000 0fE, ,—- -—:: — ‘7:L:;z:v_2000 4000 6000 8000 10000 12000 14000MICRO STRAINFig 6.13 Strain gauge C0489604020riD-40-60SPECIMEN 2 COLUMN INSIDE STRAIN GAUGE (C13-23)I\1t‘- U c...-4000 -2000 0 2000 4000 6000 8000 10000 12000 14000MICROSTRAINFig 6.14 Strain gauge C13906.3 COMPARISON WITH BENT TEST RESULTSFig. 6.15 shows hysteresis loops from test OSB2. The displacement at the columntip of specimen 032 at t=1 was 1.25” and the displacement of OSB2at the joint for thesame level of ductility was around 0.3”. This difference is partly due to the simplifiedboundary conditions of the specimen 0J2. i.e. the roller bearing of the specimen 032 willstop the vertical movement of the cap beam at that location and also the bearings did notfunction as expected. The pin allowed the specimen to slide a little instead of allowingrotation. This can be seen in the load displacement curve of specimen 0J2 (Fig.6.8) by thesudden change in stiffness close to zero displacement in both pulling and pushing.OAK STREET BRIDGE TEST No. 2r/150100500r;)-50. -100-150-3 -2 -1 0 1 2 3 4 5JOINT DISPLACEMENT (in)Fig 6.15 Hysteresis loop of bent test 2 (OSB2)91The cap beam of both the Joint specimen OJ1 and the Bent specimen OSB1 failed inshear (Fig.6. 16 and 6.17). The major shear crack of OSB1 starts at the top of the capbeam exactly 5.0 ft away from the center line of the column. This crack propagatestowards the column at angle of around 45 degrees. In the specimen OJ1, as the twobearing positions in the cap beam are 2’2” shorter than the full bent, the major shear crackoriginated closer to the column (4.0 ft from the center line of the column) and it extendedat a much steeper angle (50 degrees) to the longitudinal axis of the cap beam (Fig. 6.18).The specimen OJ1 cap beam carried a maximum shear force of 49.7 kips at yield. Thiscompares with the 53.6 kip shear force carried by the cap beam of specimen OSB1(Appendix B Figs. B5 and B6).92Fig.6. 16 Cap beam cracking specimenOJ1Evw0? nIC 31aZI3IbWV 103d$ I£2 JLS3 iN\Fig. 6.17 Cap beam crackingSpecimen OSB1930CFig. 6.18 Crack pattern of OJ1 and OSB 1In joint specimen 0J2 and bent specimen OSB2, the crack pattern and spacing ofcracks in the columns are very similar to each other (Fig. 6.19 and 6.20). Initially thecolumn flexural cracks started closer to the joint and extended down to the middle of thecolumn in the subsequent sequences. It is difficult to compare crack patterns at differentsequences for the 0J2 and OSB2 specimens as the load displacement relationships weredifferent. There were very few cracks in the cap beams of specimen 0J2 and OSB2ascompared to the Specimens OJ1 and OSB1. The shear force carried by the cap beam andthe column of specimen 0J2 were 67.4 kips and 50.5 kips respectively. These values arecomparable with the shear carried by the cap beam and the column of OSB2 80.2 kips and56.4 kips respectively (Appendix B Figs. B13 and B 14).vertical jackQ horizontal jackpin bearing.roller beanng-Fig. 6.19 Column crackingspecimen 0329495O1 A.LflBE:3 30NS8S0 N3WE:66L D3OJ.S3.L .LN3SOOIO-IFig. 6.20 Column cracking specimen OSB2,96CHAPTER 7SUMMARY AND CONCLUSIONSThe two primary objectives of this project were to construct a test frame to testconcrete components and to test two large scale specimens. Using the test frame, differentinpiane load combinations can be applied on different size specimens and configurations.i.e. joints, beams and columns. The number and the type of the boundary conditions at thebottom of the specimen can be changed to suit the test requirements. As the test frame isself equilibrated, external reactions are not required to equilibrate the jack loads appliedduring testing ofthe specimen.To find out the behaviour of Oak Street Bridge bent due to lateral slow reversedcyclic loading, two half bent sections (as built and retrofitted) at 0.45 scale were tested.Both specimens were built using the existing material properties of the bridge. The fullbent test were carried out by others and reported elsewhere (Anderson et al., 1994).Brittle shear failure was anticipated in the cap beam of the as built specimens, i.e. inthe middle third of the cap beam gage 4 stirrups were spaced at 1 ‘4”. Therefore cap beamof the first specimen was tested for anticipated shear force due to dead and lateral loading.Because of limitations in the equipment, particularly the inability to impose vertical loadsimulating dead load on the cantilever of the bent, a load system was organized thatprovided the required shear in the cap beam at section x-x, but did not fully duplicate theloading situation at the other sections. The cap beam of this specimen failed in shear asexpected. The measured lateral load vs displacement hysteresis loops (Fig.6. 1) showed97very significant strength degradation and pinching as expected. This particularmode offailure is associated with large deterioration of strength and stiffliess whichleads to suddenfailure of the structure. The final failure mode of specimen OJ1 and OSB 1 (MOTHfullbent test) were similar (shear crack starting at the top of the cap beam andpropagatingtowards the column). The specimen 011 cap beam carried a shear force of 49.7 kipsatyield and the magnitude of the shear force carried by the specimen OSB1at yield was 53.6kips (Appendix B Figs. B5 and B6).The cap beam of the second specimen was retrofitted by post-tensioning it withDywidag bars. In the second specimen the loading pattern closelyduplicated that of thefull bent test for both the column and the cap beam. Post-tensioned cap beam ofspecimen0J2 carried 35% higher shear force than that of OJ1 withoutany significant cracking inthe cap beam (there is a small increase in shear capacity dueto the increase of compressivestrength of concrete of the second specimen from 26 MPato 33 MPa). This increase inshear capacity of the cap beam indicates that the post-tensioning is an effectivemethod ofimproving the shear capacity of the cap beam. This was verified by both full andhalf benttests. The strains in the cap beam top and bottom bars of the post-tensionedspecimen(0J2) are very low due to the high compressive force in thecap beam compared to the asbuilt specimen (OJ1). The last cycle (4’ pushing) shows considerable stifihess degradation.As the stroke of the lateral loading jack was not sufficient, the specimens couldnot beloaded up to complete collapse.Propagation of flexural cracking in the column of specimen 0J2 and OSB2weresimilar. The large displacements of the column of the 0J2 specimencompared to theOSB2 specimen will result in a higher moment in the column due to the P-Aeffect of the98column axial load. The ultimate strengths (base shear) of specimen 0J2 and OSB2 werecomparable, i.e.the applied maximum lateral load for 0J2, 50.5 kips was close to half thelateral load applied on the OSB2 which was 105.5 kips. The shear force carried by the capbeam and the column of the specimen 0J2 were 67.4 kips and 50.5 kips respectively.These values are comparable with the shear carried by the cap beam and the column ofOSB2 which were 80.2 kips and 56.4 kips respectively (Appendix B Figs. B13 and B 14).There were large displacements of the OJ specimens compared to the OSBspecimens. The main reason for this large displacements were the upliftat the rollerbearing and the unexpected sliding at the pin bearing. The uplift could have been reducedby either tightening the bolts at the roller bearing or using a tie down at the roller bearing.The sliding at the bolts of the pin bearing could have been avoidedby using a cylindricalroller as the pin bearing. It is also important to develop a more extensive displacementmeasurement system so that the displacements at the column tip of the half bent specimenscan be related to the displacements at the joint of the full bent structure.Although the stirrups and tie strain gauge values seems to be unreliable, most of thestrain gauges in the main bars of the column and the cap beam of the two specimensshowed reasonable strains.This first series of tests on the test frame has demonstrated the ability to closelyreplicate tests on larger specimens, however there werea number of problem areas thatcould be improved in the future.99It is recommended that additional load capabilities be added. In the case ofreplicating tests such as the full bent tests, additional jacks could apply the equivalent deadload on the cantilever. The remaining limitation on the force system would be the lack ofability to impose flexure at the centerline of symmetry of the full bent. This is a dead loadeffect that becomes less important as the lateral load is increased.A number of difficulties occurred due to the simplified bearing design. In a futuretest, it is recommended that fi.ither attention be given to the details of the bearings toeliminate even small vertical motions, which lead to overall rotation of the specimen. Inaddition, the bearing dimensions affect local conditions in the disturbed region. Since shearis of major importance, bearing details are also important.The behaviour of the specimen could be monitored better if more extensivedisplacement measurements were made. It is recommended that these be devised tocapture curvature and displacement throughout the specimen, and to establish the rigidbody rotation so that actual displacements, relative to any reference system, can be readilydetermined.REFERENCESAnderson, D.,Sexsmith, R., and Seethaler, M., “Oak St. Bridge Two Column Bent Test”,Report to the Ministry of Transportation and Highways, British Columbia, 1994.Collins, M.P., and Mitchell, D., “Prestressed Concrete Structures “, Prentice Hall, 1991.Hanson, N.W., Connor, H.W., “Seismic Resistance of Reinforced Concrete Beam-ColumnJoints “ Journal of the Structural Divison, ASCE, Vol. 93, No. ST5, Proc. Paper 5537,October1967,pp533-560.Jirsa, J.O., Meinheit, D.F., and Woollen, J.W., “Factors Influencing the Shear Strength ofBeam Column Joints “ Proceedings of the U.S. National Conference on EarthquakeEngineering, Ann Arbor, Mich., June 1975,pp297-305.Kawashima, K., and Koyama, T., “Effects of Cyclic Loading Hysteresis on DynamicBehaviour of Reinforced Concrete Bridge Piers” Structural Eng.fEarthquake Eng.Vol. 5,No.2,343 s-3 50s,October 1988 Japan Society of Civil Eng.Kennedy, D.W., Turkington, D.H., and Wilson, J.C., “Design for Earthquake Retrofit andWidening of the Vancouver Oak Street Bridge.” Presented at CSCE Annual ConferenceQuebec City, May 1992.100101Koyama, T., and Kawashima, K., “Effect of Number of Loading Cycles on DynamicCharacteristics of Reinforced Concrete Bridge Pier Columns” Structural Eng.fEarthquakeEng. Vol 5. No.1,183s-191s,April 1988 Japan Society of Civil Engineers, Pg.205-213.Leon, R.T., “Shear Strength and Hysteretic Behaviour of Interior Beam Column Joints”,ACI Structural Journal,V. 87,No. 1 ,January-February 1990, Pg.3 -11.Meinheit, D.F., and Jirsa, J.O., “Shear Strength of Reinforced Concrete Beam ColumnConnections “November 198 1,ASCE, Vol. 107, No. ST1 1.Mitchell, D., Sexsmith, R., and Tinawi, R., “Seismic Retrofitting Techniques for Bridges -A State of The Art Report.”, CJCE, Vol. 21, No. 2, April 1994.Panta.zopoulou, S., and Bonacci, J., “Consideration of Questions about Beam ColumnJoints” ACI Structural Journal, V.89,No. 1,January-February 1992, pg.27-36.Park, R., and Paulay, T., “Behaviour of Reinforced Concrete External Beam-ColumnJoints Under Cyclic Loading “ Fifth World Conference on Earthquake Engineering,International Association for Earthquake Engineering, Rome, Italy, 1973, Paper No. 88,pp772-781.Park, R., Rodriguez, M.E., and Dekker, D.R., “Assessment and Retrofit of a ReinforcedConcrete Bridge Pier for Seismic Resistance”, Earthquake Spectra, Vol. 9, NO. 4, 1993,Pg. 78 1-801.102Paulay, T., and Priestley, M.J.N., “Seismic Design of Reinforced Concrete and MasomyBuildings” John Wiley and Sons,Inc.,1991.Pessiki, S.P., Conley, C., Bond, T.,Gergely, P., and White, R.N., “ReinforcedConcreteFrame Component Testing Facility Design, Construction, Instrumentationand Operation”,National Center for Earthquake Engineering Research, SUNY, Buffalo, 1988.Rogers, G.C., “A Seismotectonic Overview of the Pacific Northwest” EERI’ 93 AnnualMeeting, Seattle, Washington.Seethaler, M., “Oak St. Bridge Bent Test Slow Cyclic Testing”,M.A.Sc. Thesis,University of British Columbia, April, 1994.CPCA, “Concrete Design Handbook”, Canadian Portland CementAssociation, Ottawa,1985.CISC, “Handbook of Steel Construction”, Canadian Institute of Steel Construction,Ontario, 1984.AASHO, “Standard Specifications for Highway Bridges”, Eighth Edition, 1961.Canadian Standards Association, Design of Highway Bridges,CAN/CSA-S6-88, June1988.103MOTH, “Seismic Rehabilitation of Bridges”, Report by Ministry of Transportation andHighways, British Columbia, 1992.APPENDIX AANALYSIS AND DESIGN OF THE TEST FRAMEIn the initial analysis of the steel test frame a safety factor of 1.25 was used for thejack loads.Analysis ofthe beam:The top girder (AB) was analysed as simply supported. The two vertical jackswere assumed to be on either side ofthe center line of the girder.Limits:-1250 <P1 < 1250 kN.-1250 <P2 < 1250 kN.0<a <1.25m0<b <1.25mP1, P2 are vertical Jack Loads and a,b are horizontal distances by which those canbe moved in each direction from the center line of the girder. In the analysis of the topgirder two cases were considered. Those were when the vertical jacks acting inthe samedirection and when they were acting in the opposite direction.104105Analysis of the column:For the above locations and magnitudes of vertical jack loads assumed beam FG asfixed to find the end reactions and moments of the columns. (Fig. 2.2)Columns were then designed for the maximum axial forces and moments found fromthe above analysis and for the horizontal jack force P3.-1250 <P3 < 1250 kN.0.5 <C < 3.0 mWhere P3 is the horizontal jack load and C the range of that jackThe truss members FD,DC,ED,BD were analysed as pinned and to carry thehorizontal jack force of 1250 KN.The floor beam was analysed for the following load cases.1 .When the vertical jack forces are in the same direction2.When the vertical jack forces are in the opposite directionsFor each case lateral loading jack direction and the position of each jack waschanged to find the maximum reaction forces on the floor beam.After analysing the structure for the above load cases initial sizing of members ofthe frame were done using the handbook of steel construction.(CAN3 - S16. 1- M84PART 1)Then using the computer program STAAD and with 32 load combinationsconfirmed the member loads and deflections are within the permissible values.106This frame is capable of supporting two 1000 kN. vertical jacks and one 1000 kN.horizontal jack. The maximum allowable forces and range of positions of the jacks areshown in Figure 2.1 The height of the horizontal girder (W610*241)can be changed tosuit the specimen size. For the above arrangement, the jacks are capable of exsertingdifferent combination of forces on required region of the specimen.Maximum forces obtained using STAAD III / ISDS (STructural Analysis AndDesign / Integrated Structural Design System)Table A. 1 Maximum frame member forcesMEMBER B.M.(kNm) SHEAR(kN.) AXIAL(kN.)GF 1200 1400 400AG 1200 400 1400FB 900 1000 1700FC,ED,DB 0 0 1400AC 800 1600 1000In the girder to column joint design tried to reduce the moment transferredbetween members by assuming semi rigid connections. But the reduction in moment thatcan be achieved was negligible. Therefore reduced the vertical jack loads to the valuesshown in the Fig.2. 1 And then the joints were analysed both as pinned and fixed and weredesign for the maximum forces obtained by those analysis.107APPENDIX BFORCE RESULTANTS OF OJ1 AND OSB1The Figs. B 1 and B2 gives the maximum loading on OJ1 and OSB 1. Figs. B3 to B8 areaxial force, shear force and bending moment diagrams for maximum loading. Units arekipft.159.05j•4—øx51.4 10109.3 49.7Fig. B.1 Maximum loading on OJ1(dimensions in Fig. 6.2)I64.5” 67.5”I67.5”i64.5”26Iloadiri frame- 140eel16V 171 4331—A1825.7..__22T52.1147.956.7” 165.6” 56.7”U).0,I IFig. B.2 Maximum loading on OSB110851.4Fig. B.3 Axial force on OJ11 216 1752.118147.922Fig. B.4 Axial force on OSB110951.4i—id1049.7159.0Fig. B. 5 Shear force on OJ126.5_____40.0______1 1411R1733.11825.722Fig. B.6 Shear force on OSB111011________0.1 155.35,1.L.Z910385.5Fig. B.7 Bending moment on OJ1366.5164.0164.0i6Q2.0A 17202.096.6 7Z——.OFig. B.8 Bending moment on OSB1111FORCE RESULTANTS OF 0J2 AND OSB2The Figs. B.9 and B. 10 gives the maximum loading on OJ1 and OSB1. Figs. Bi ito B16are the axial force, shear force and bending moment diagrams for maximum loading.180.550.512111 7 1023.0 90.1 67.4Fig. B.9 Maximum loading on 0J2(dimensions in Fig. 6.8)105.5261141756.4A’84914—22T140186.0Fig. B.10 Maximum loading on OSB2112180.5 1213 650.5Fig. B. 11 Axial force on 0J22613 4 16 17]8186OFig. B. 12 Axial force on OSB211350•5F]1223.0_IL‘b13 5 7 1O67.4157.5Fig. B.13 Shear force on 0J2261 240.0_____ ____________________4 1611740.10.2I40.280.256.418 49.1U22Fig. B.14 Shear force on OSB211437/6 7/1069.0/44.3‘447.8Fig. B. 15 Bending moment on 0J2550.4397)_._/164.’26 164.01 27444.591 1I617280.5/754.1Fig. B. 16 Bending moment on OSB2CCl, CD CD C) CDCl) CD C) CDc)—‘.D“Drj -,.-‘.-‘I—I—I••-‘DO000000-ui.l)L)•r, -,o’o’o’ac’ac’..c.---.t’3CO’C-4JCv —t’3f’.)L34-DUiCL)-C-C,ODe r, -,CD C) I i C) 0 0I...L\.).UiQ--UiC00CI—.ViVil2-,-,,...‘UiVi--Cpp.’—C00—‘-Q’00\D-00ViT v -,CD•‘—4CD‘-4 t’J --—-40 )CDCD CD C)C) 0ci) C


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