Structural behaviour of reinforced concrete beams with high yield strength stirrups

Abstract

Primary national codes and standards for reinforced concrete (RC) members and structures specify a limit value of stirrup yield strength. The salient reason for this restriction is to control diagonal crack widths, which lead to shear tension failure. The influence of a high yield strength of stirrups on the failure mode of such members is thus of great concern. To investigate this issue, 12 RC beam specimens incorporating stirrups with high yield strength were tested. The test variables employed in the study were three levels of stirrup spacing and four levels of stirrup yield strength. Assessment of the test results was conducted by analysing the variation of both spacing and number of diagonal cracks due to an increment in the total amount of stirrups. An evaluation of diagonal crack width measured under the service load level was also performed. The test results showed that the diagonal crack width under the service load level is affected by the yield strength of the stirrups and the stirrup spacing. In addition, the number of diagonal cracks increased and the spacing of the cracks reduced as the amount of stirrups was increased. Overall, the average diagonal crack width of all the specimens incorporating high yield strength stirrups was less than the 0·41 mm recommended in ACI 224R-01.