UBC Theses and Dissertations
Response of reinforced concrete to reverse cyclic loading Fronteddu, Luciano Fabio
This thesis investigates the response of cracked reinforced concrete subjected to reverse cyclic loading with particular emphasize on the contribution from tensile stresses in cracked concrete. An iterative strain compatibility approach using a nonlinear bond stress-slip relationship was implemented into a computer program. The program indicated that monotonic tension stiffening does not decay with increasing strain. Analyses also demonstrated that the variation of slip along a reinforcing bar is approximately linear, which allowed the development of a simple transparent tension stiffening model that could be presented in equation form. This model indicated that in addition to being proportional to the square root of the concrete strength, the reinforcement ratio, and inversely proportional to the bar diameter, tension stiffening is directly proportional to the crack spacing. To better understand tension stiffening under reverse cyclic loading, the bond model was enhanced by adding a reverse cyclic bond stress-slip relationship. An empirical reverse cyclic tension stiffening model was developed, based on the data obtained from an experimental program. This involved testing 5 large-scale reinforced concrete elements under reverse cyclic axial load. The parameters which were investigated were the amount of concrete surrounding the reinforcement, as well as the load history. A model for reinforcing steel, which was selected from the literature, was modified in order to generalize the model for different types of steel. A simple model for the concrete in compression was also selected from the literature. The analytical models were combined into a computer program which can predict the complete reverse cyclic axial response of reinforced concrete.
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