Explicit analytical model for seismic shear strength of RC bridge columns

An explicit analytical model was developed to predict the seismic shear strength of reinforced concrete ( RC) bridge columns that failed in different modes including flexure, shear and flexure-shear failure. Shear demand was calculated without iteration based on sectional analysis. The shear capacity was divided into three contributions: the concrete compression zone (CCZ), concrete tension zone, and transverse reinforcements. Rankine's concrete failure criteria were used to determine the contribution of the CCZ, while modified compression field theory was applied to predict the other contributions. The three contributions were found to be dependent on the bottom section curvature based on axial-shear-flexure interaction. Seismic shear strength was obtained with a degraded shear capacity equal to the shear demand. Numerous tests were used to verify the proposed model and to assess the methods proposed in existing codes. Based on the proposed model, an application example and parameter analyses were conducted. The results showed that the proposed model produced better agreement with the test data than the methods of current codes. The contribution of the CCZ dominates RC bridge columns with low transverse reinforcements or high axial load ratios. The influence of the axial load ratio on seismic shear strength can be revealed accurately by the proposed model.