Postfire Seismic Responses of High-Strength RC Columns: Experiments and Simulations

Abstract

Significant research has been conducted in the field of high-strength RC. This body of work encompasses a wide range of topics from material behavior to seismic performance, which has been instrumental in shaping design codes for high-strength RC structures. However, a notable gap remains in understanding the postfire seismic behavior of high-strength RC members. This study addressed this gap by conducting experimental tests to explore the seismic behavior of high-strength RC columns after fire exposure. The experimental program subjected column specimens to both fire exposure and cyclic loading tests, with key variables including varying concrete strengths and a standard 2-h fire exposure. This study extensively analyzed the impact of fire exposure on seismic performance, focusing on temperature gradients, damage patterns, load-displacement hysteresis responses, displacement composition, and plastic region length. The results indicated that fire exposure caused more significant structural degradation in high-strength concrete (HSC) columns compared with normal-strength concrete (NSC) columns. Specifically, fire exposure moderately reduced the peak strength of NSC and HSC columns by 8% and 12%, respectively, and significantly decreased their initial stiffness by 48% and 55%, respectively. Despite considerable spalling in the cover concrete of the HSC column, the core concrete and longitudinal reinforcement remained largely intact, effectively sustaining the postpeak behavior under cyclic loading. Complementing the experimental work, the study also proposed suitable computational models to simulate the postfire seismic responses of NSC and HSC columns. These models aim to enhance the predictive understanding of structural behavior in postfire scenarios, contributing valuable insights for the design and assessment of fire-affected RC structures.