Postfire Mechanical Behaviors of Grouted Sleeve Connections Under Strong Earthquakes

An experiment with 30 specimens was carried out to investigate the mechanical behaviors of postfire (temperature up to 800°C) grouted sleeve connections under different loading regimes, including uniaxial tensile loading and cyclic loading with a large strain. The load versus displacement curves of postfire grouted sleeve connection specimens included ascending, yielding, hardening and declining segments and could be classified into two kinds of curves according to the shapes of ascending and descending segments. Corresponding to the types of load versus displacement curves, there were two failure patterns, including rebar fracture outside the sleeve and bond-slip failure between the grout and steel rebar. The critical temperatures for causing the failure pattern change and loading bearing ability decline were 400°C and 800°C, respectively. It was found that an influencing factor of 0.178 was used to represent the accumulated damage from cyclic loadings, which formed the theoretical methods for the bearing capacity calculation of postfire connections. In addition, the displacement ratio was proposed to be 6.0 for the postfire grouted sleeve connection under different loadings. All of these findings and analyses are beneficial for the design of grouted sleeve connections after exposure to elevated temperatures.