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UBC Theses and Dissertations

Seismic shear capacity of reinforced concrete elements Webster, Scott William Frederick


The objective of this thesis was to develop a better understanding of reinforced concrete columns with minimal (widely spaced) transverse reinforcement subjected to reversed cyclic shear. This thesis involves three main parts which are described below. A rational model for the shear capacity of reinforced concrete is developed which takes into account the effect of previously existing diagonal cracks. The model is an extension of the modified compression field theory which is one of the most advanced shear design methods. The model was implemented into a computer program, and predictions based on this proposed method are compared to other shear design models. A copy of the program is included in the thesis. To forward the development of a seismic shear model, an analytic study was undertaken in which the magnitude of stresses (both compressive and shear) at an arbitrarily inclined crack were investigated. In addition, by means of a literature review, the degradation of aggregate interlock across a crack interface when subjected to reverse cyclic loads was studied. In addition to the analytical work a pilot experimental program was carried out, in which eight reinforced concrete bridge column elements were subjected to reversed cyclic loading. The columns were subjected to different load combinations (axial load, bending moment and shear), and had different distributions of longitudinal reinforcement. The results of the testing program is compared to predictions based on the analytical model presented earlier and other shear design models. An important part of this study was the construction and calibration of an element testing apparatus which was used to test the specimens. The experimental program also proved valuable as a pilot study, where much was learned about the operation of the tester and the most appropriate specimen connection details. The testing apparatus has subsequently been used to test a further 12 specimens as part of this ongoing study.

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