Reversed-Cyclic Response of Shear-Critical Rectangular Bridge Columns

Abstract

The results of an experimental program comparing the responses of shear-critical rectangular columns tested under monotonic and reversed-cyclic loading are presented. These specimens had a constant compressive axial load and varying amounts of transverse reinforcement. Comparisons of the monotonic and reversed-cyclic loading responses are discussed. The reversed-cyclic peak shear strengths were about 11% and 17% lower, on average, than the monotonic peak strengths for the positive peak and the negative peak, respectively. Response predictions were made for columns from this experimental program, as well as for tests by other researchers, on rectangular shear-critical columns. Prediction methods included those based on current load and resistance factor design (LRFD) standards and seismic guidelines with and without an included strut, as well as nonlinear finite-element analysis. Methods based on official standards and guidelines gave similar conservative results for the shear strength. It was concluded that the addition of the horizontal components of inclined struts associated with the compressive axial loads to the sectional predictions improved the strength predictions by about 37% on average. In addition to providing accurate shear strength predictions, nonlinear finite-element analysis is capable of predicting the complete member response and accounts for the combined contributions of the concrete, transverse reinforcement, and inclined strut action from the applied axial compressive load.