Abstract: Two tests were carried out respectively in this research, one to investigate the variation of the compressive strength of concrete, and one to investigate the seismic performance under high temperature. Comparing the unfired specimens and the fired specimens, through the study of concrete failure modes, using SPSS statistical analysis software to process the changes of temperature and compressive strength, the relationship between temperature standing time and compressive strength was obtained. Through the analysis of the skeleton curve, stiffness, ductility and bearing capacity of fired specimens, the following conclusions can be drawn: after high temperature, the yield load, peak load and ultimate load of the specimens are significantly reduced; while the shear load increases with the axial compression ratio, however when the axial compression ratio proceeds exceeds certain limit, the shear load decreases. Furthermore, a shear capacity formula was proposed, which can be used to identify the extent of building damage after a fire hazard.

Key words: concrete materials, failure modes, compressive strength, seismic performance, shear capacity