Improved Analytical Model for Shear Strength of Circular Reinforced Concrete Columns in Seismic Regions

Revisions to the three component model for seismic shear strength of circular columns developed at UCSD are discussed in this paper. The revisions suggested account for the effect of the concrete com-pression zone on the mobilization of the transverse steel, as well as the effect of aspect ratio and longitudinal steel ratio on the strength of the concrete shear resisting mechanism. The proposed model is compared with the previous UCSD model, as well as the design approaches of the ATC-32 and Caltrans Memo 20-4 through the use of an experimental database consisting of 47 circular reinforced concrete bridge columns. For comparative pur-poses, the proposed model is also compared with the ATC-40 assess-ment approach. Results are presented in the form of the ratio of experimentally recorded strength to design strength versus various key design parameters.