Uniaxial tensile behavior of half-grouted sleeve connections with concrete cover after exposure to elevated temperatures

Abstract

This study presents the tensile behavior of a half-grouted sleeve connection (HGSC). A total of 15 prism samples of grout are subjected to a series of tests before and after exposure to various temperatures. A total of 75 eccentric HGSC specimens with a 40 mm concrete cover and 15 central HGSC specimens without a concrete cover were fabricated for uniaxial tensile loading tests. A pseudo-transient heating regimen was applied to HGSC specimens with concrete covers; the specimens were heated to the desired temperature and left there for a duration of 0 min. This study systematically investigates the tensile properties of post-fire HGSC specimens to assess the combined effects of peak environmental temperature (20 °C, 200 °C, 400 °C, 600 °C, 800 °C), concrete cover depth (0 mm, 40 mm), concrete strength grade (C30, C35, C40, C45, C50), and concrete spalling (burst or unburst). The failure mode, load–displacement curves, sleeve strain distribution, and heat transfer are employed to characterize the response of the HGSC specimens, which is subsequently discussed. It is discovered that, although concrete compressive strength plays a minor role, temperature, concrete cover, and explosive spalling significantly influence certain post-fire tensile parameters of the HGSC. Based on the results, there is considerable potential for determining the ultimate tensile force in HGSC specimens with concrete covers and the remaining compressive strength of grout using ultrasonic pulse velocity detection. Furthermore, a comparative accuracy analytical model, incorporating the influence of tangential strain derived from the experimental results, is established based on confinement stress.