UBC Theses and Dissertations
A study of wood-based shear walls sheathed with oversize oriented strand board panels He, Ming
A new wood based shear wall system built with nonstandard large dimension oriented strand board panels has been developed. The project described in this thesis consists of studies to 1) experimentally investigate and quantify the structural performance of the new shear wall system under monotonic and cyclic lateral loading conditions, considering different types and spacings of panel-frame nail connectors, and 2) analytically predict and model the performance of the new shear wall system. A test facility has been built for full scale shear walls of up to 2.4 x 7.3 m in dimension where both lateral and vertical loads can be applied simultaneously onto the wall assembly. The experimental program has been divided into a static and a cyclic test phase. Thirteen shear wall systems with standard 1.2 x 2.4 m and with oversize panels have been tested to investigate the influence of 1) panel size, 2) panel-frame nail connector type, 3) panel-frame nail connector spacing, and 4) cyclic loading protocol on the overall shear wall behaviour. A database on the structural performance of wood based shear walls sheathed with oversize oriented strand board panels has been generated. The database includes information on strength, stiffness and ductility properties, energy dissipation and failure modes of shear walls under different testing conditions. A substantial increase in both stiffness and lateral load carrying capacity was achieved by shear walls built with oversize panels as compared to standard panels. A further reduction in nail spacing around the perimeter of the full size panel increased the lateral load resistance to more than double that of regular walls. The failure modes in the shear walls were shown to be substantially different under monotonic and currently used cyclic test conditions. The former was mainly nail withdrawal while the latter was dominated by low cycle nail fatigue failures. A new cyclic loading protocol was proposed and tested, which resulted in failure modes similar to those observed in dynamic earthquake tests. In examining the dissipated energy as the area under the load deformation curve, it seems that the walls built with the standard panels can dissipate more energy under cyclic loading, compared to the walls built with oversize panels. Furthermore, a group of tests has been conducted to investigate the load-slip characteristics of panel-frame connectors. A nonlinear finite element analysis program has been adopted to predict and model the performance of shear walls built with oversize panels. The program results had good agreement with the initial part of the nonlinear behaviour of the shear walls in the tests, which is before the panelframe connectors failed. It could not, however, follow the test results when the connectors failed and further refinements to the program have been suggested to incorporate nail failure occurrence.
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