To implement performance-based earthquake engineering (PBEE), it is necessary to assess the probability of reaching multiple damage states in structural and nonstructural elements. To help with this assessment, the research presented in this report provides practical recommendations for estimating the likelihood that in a reinforced concrete column the concrete cover will have begun to spall or the longitudinal bars will have begun to buckle, based on the column’s expected deformation demand.
Damage development in reinforced concrete columns is complex, involving three- dimensional material and geometrical nonlinearities in the concrete and reinforcing steel, as well as the interaction between the e xpansion of the concrete core a nd the restraint provided by the transverse reinforcement. Modeling such damage in detail challenges the most advanced and computationally demanding modeling strategies that are currently available. To develop recommendations that can be implemented easily in practice, this research relied on moment- curvature analysis and plastic-hinge analysis to predict trends in concrete compressive strain, plastic rotation, drift ratio, and displacement ductility at the onset of damage as functions of various key column properties (e.g., axial load ratio and aspect-ratio). The models were calibrated with existing experimental results from the UW-PEER reinforced concrete column performance database, which documents the performance of more than 450 columns.
The ratio of the observed displacement at bar buckling to the calculated displacement had a mean of 0.97 for spiral-reinf orced concrete columns and 1.00 for rectangular-reinforced concrete columns. The corresponding coefficients of variation for thes e ratios were 25% and 26%, respectively.
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