Cracking and Tension Stiffening Behavior of High-Strength Concrete Tension Members Subjected to Axial Load

This paper presents the test results of 35 direct tensile specimens to investigate the effect of concrete strength on the tension stiffening effect and cracking response in axially loaded reinforced concrete tensile members. Three concrete strengths 25, 60 and 80 MPa were included as a major experimental parameter together with six concrete cover thickness ratios. The results showed that as higher strength concrete was employed, not only splitting cracks along the reinforcement more extensive, but also the transverse crack spacing became smaller. Thereby. the effective tensile stiffness of the high-strength concrete specimens at the stabilized cracking stage was much smaller than those of normal-strength concrete specimens. This observation is contrary to the current design provisions, and the reduction in the tension stiffening effect by employment of high-strength concrete is much greater than that would be expected. Based on the present results. a modification factor is proposed to account for the effect of the cover thickness and the concrete strength.