Reliability analysis of the residual moment capacity of high‐strength concrete beams after elevated temperatures

Abstract

AbstractA series of tests were conducted to study the variability of the residual compressive strength for high‐strength concrete (HSC) after elevated temperatures, and then a calculation process was developed to study the reliability of the residual moment capacity of HSC beams after a fire. The experimental results indicated that the mean values and the characteristic values of the residual compressive strength of HSC were reduced with the increasing elevated temperatures. The standard deviation of the residual compressive strength of HSC was increased when the temperature ranged from 20 to 400°C and decreased from 400 to 800°C. Regardless of the elevated temperatures, the residual compressive strength of HSC followed the normal distribution. The reliability index of the residual moment capacity of HSC beam was decreased with the increasing fire duration. The decrease rate of the reliability index became lower and kept constant when the section height–width ratio was beyond 2.75 and the longitudinal reinforcement ratio was higher than 1.43%. As the load effect ratio was increased, the decrease rate of the reliability index was reduced regardless of the section size, the height–width ratio, and the reinforcement ratio.