Experimental and theoretical study on shear behavior of HRB600 reinforced concrete beams after high temperature exposure

Abstract

To investigate the variation pattern of shear performance in HRB600 RC beams after exposure to high temperatures (i.e., 200 °C, 400 °C, 600 °C, and 800 °C), 4 plain concrete beams were tested for temperature field. Additionally, 15 RC beams with shear span-to-depth (a/d) ratios of 1.2, 2, and 3 were subjected to four-point bending tests at room temperature and after high temperatures. The test results analysis focused on the effects of temperature and shear span-to-depth ratio on the failure pattern, concrete strain, load–deflection curve, and shear bearing capacity of the RC beams. The results demonstrated that increasing the shear span-to-depth ratio from 1.2 to 3 resulted in approximately 61.6 %, 51.8 %, 57.9 %, 53.0 %, and 55.5 % decreases in the ultimate bearing capacity of RC beams at 25 °C, 200 °C, 400 °C, 600 °C, and 800 °C, respectively. The load capacity of the test beam only decreased when the exposure temperature exceeded 600 °C, with the beam (a/d = 2) exposed at 800 °C exhibiting the most significant decrease of 32.4 % compared to room temperature. Finally, a method for determining the material parameters for the structure after exposure to high temperature is proposed. This method considers the sectional temperature field and is applied to the shear resistance calculation model at room temperature. The results indicate a strong agreement between the experimental and calculated values for both heated and unheated beams.