Abstract：In order to investigate the stress-strain relationship for stirrup-confined concrete after freez-thaw cycles，two series of concrete specimens(150 mm×150 mm×450 mm) with stirrup characteristic values of 0.317 and 0.145 respectively were exposed to rapid freeze-thaw cycles in water according to GBJ82–85. The axial compressive loading tests were carried out to obtain the complete stress-strain curves of confined concrete. Test results of 46 specimens show that，with the increase of freeze-thaw cycle number，the complete stress-strain curve becomes more flat，the peak stress decreases and the peak strain increases；with the same number of freez-thaw，the reduction of the peak stress and the increase of the peak strain are more serious for lower strength concrete. Moreover，damage appears at the bonding interface between stirrups and concrete due to freeze-thaw action，and the confining effect of the stirrups is weakened for lower strength concrete. Based on the test results，theoretical complete stress-strain curve equations for confined concrete subjected to freeze-thaw cycles are established. The equations could be used for nonlinear analysis of reinforced concrete structural elements experienced to freeze-thaw cycles in cold regions.
