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Assessment of existing reinforced concrete (RC) structures after an earthquake is a challenging task that must somehow relate qualitative and quantitative observations in the plastic hinge regions and the associated residual deformation capacity of damaged structures. Having an estimate available for the remaining drift capacity will result in more economical and informed decisions regarding demolition or strengthening options. This study aims to develop a practical methodology to estimate the maximum drift demand of an RC column based on the residual crack width. For this purpose, fiber-based frame elements are used to model the RC column considering appropriately concrete behavior in compression and tension stiffening effects. Afterwards, the accuracy and reliability of the proposed methodology are demonstrated by validating the computational approach with two cyclic experimental results from literature and new test data for a one-bay one-story RC frame conducted within the course of this study. A comprehensive parametric study is performed for RC columns with different axial loads, longitudinal and transverse reinforcement ratios, and ground motions to exhibit the stochastic behavior. The study identifies the axial load ratio as the predominant parameter. Key findings include strong correlations between maximum drift ratios and total residual crack widths, as well as maximum compressive strains, with regression analysis yielding equations for accurate drift ratio estimation. Simple predictive models are proposed to estimate the maximum deformation demands based on observed residual crack widths. Residual cracking exceeding 5 mm poses significant risk for the columns with axial load ratios above 0.4, with 90% probability of exceedance 2% drift ratio. [ABSTRACT FROM AUTHOR]

Samos Earthquake caused the collapse of about fifty buildings in İzmir city center, resulting in over 120 fatalities. The response spectra of the ground motions at the soft soil sites in Izmir revealed that the spectral accelerations in the period range of 0.5–1.5 s are similar to the spectral accelerations defined by the response spectrum corresponding to the 72-year return period. Despite experiencing accelerations lower than those defined by the Turkish Code design spectrum (475-year return period), significant damage was observed due to the deficiencies of the building stock. Several factors such as soft story, lack of code-compliant transverse steel reinforcement, and low concrete strength have contributed to the devastating loss. Studies in the last two decades on deformation capacity estimation of RC columns showed that key parameters for collapse drift limits are the axial load ratio (i.e., axial force demand to capacity ratio) and transverse reinforcement amount. Most of the collapsed buildings in the past Turkish earthquakes had low concrete strength resulting in high column axial load ratios with limited drift capacity. In order to identify the collapse of vulnerable buildings, a simple procedure is proposed based on vertical and lateral pushover analysis results. The method relies on estimating the average axial load ratios of the most critical columns and their seismic drift demands. An axial load ratio-drift demand limit state model was developed to identify the buildings with high collapse risk. The model was validated with the damaged buildings in İzmir after the Samos earthquake to capture the buildings with poor performance even under service level earthquakes. The proposed model is practical as it only requires the floor plan and concrete compressive strength. It is found to be legitimately accurate to identify and prioritize the buildings prone to collapse. [ABSTRACT FROM AUTHOR]