Collapse of a nonductile concrete frame: Evaluation of analytical models

Abstract

SUMMARYThe current paper presents nonlinear dynamic analyses that simulate shaking table tests performed on a four-column reinforced concrete frame described in a companion paper. The frame consists of two ductile and two nonductile columns interconnected by a stiff beam. In order to validate existing analytical models for nonductile concrete columns, a blind comparison of the test data and results of the analysis is performed. The analysis adequately captures the drift response and correctly detects collapse of the structure; however, strength degradation due to cover spalling is exaggerated in the analytical model. Refinement of the analysis by changing the concrete cover model results in an excellent agreement between the test data and analysis results at the initiation of shear failure and collapse of the frame. The experimental data are further compared with lumped-plasticity nonlinear models used in engineering practice. The results suggest that the sudden strength degradation used in ASCE/SEI 41-06 results in an exaggerated estimate of the displacement demands. It is also observed that ignoring the strength degradation, using an elastic-perfectly-plastic model, provides a good estimate of the displacement demands when strength degradation is not severe.

Experimental Study and Numerical Model Calibration for Earthquake-Induced Collapse of RC Frames with Emphasis on Key Columns, Joints, and the Overall Structure

“…Journal of Earthquake Engineering, Accepted on . DOI: 10.1080/13632469.2015 experimental data, a finding similar to those obtained by other researchers [Yavari et al, 2009;Calabrese et al, 2010]. The discrepancy in stiffness produced in this work is not larger than those found in the existing literature and is therefore considered acceptable.…”

Seismic loss estimation of non‐ductile reinforced concrete buildings

“…unrestrained increase in lateral displacements for a small incremental increase in seismic demand) detected using incremental dynamic analysis. With recent progress in simulating global collapse of non‐ductile reinforced concrete frames , a new definition of collapse is introduced herein to capture the point at which a structure losses the ability to sustain gravity load carrying capacity. This collapse criterion is named the “Gravity Load Collapse” in this paper.…”

Collapse of a nonductile concrete frame: Shaking table tests

“…A companion paper (Yavari et al [25]) presents results of nonlinear dynamic analyses to simulate frame collapse considering nonlinear interactions of flexure, shear, and axial effects.…”

“…In addition to the model comparison with more cyclic data, which is essential to verify such assessment models, dynamic test results can also contribute in evaluating the model applicability in predicting dynamic structural response expected in earthquake excitations. The ability of nonlinear dynamic analysis models to capture the observed structural response is explored in a companion paper [25]. Major differences between dynamic and static tests include the strain rate effect and varied loading history determined by dynamic response of the specimen to the input base motion.…”