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 circul ar columns developed at UCSD are discussed in this paper The revisions sugg ested account for the effect of the concrete compression zone on the mobili zation of the transverse steel, as well as the effect of aspect ratio and l ongitudinal steel ratio on the strength of the concrete shear resisting mec hanism. 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 brid ge columns. For comparative purposes, the proposed model is also compared w ith the ATC-40, assessment approach. Results are presented in the form of t he ratio of experimentally recorded strength to design strength versus vari ous key design parameters.