Tension development length of large-diameter bars for severe cyclic loading

This paper presents a study on the tension development length of large-diameter reinforcing bars embedded in well-confined concrete. Pull-push tests were conducted on No. 14 and 18 (43 and 57 mm) bars to evaluate whether the development length requirements in the AASHTO LRFD Specifications are adequate for large-diameter bars subjected to severe cyclic loading. The data have been used to validate finite element models, which have been subsequently employed in a parametric study to establish a formula to determine the tensile capacity of a bar as a function of the embedment length, and the concrete and steel strengths. Monte Carlo simulations conducted with this formula have shown that the AASHTO requirements are adequate to develop the yield strength of a bar in tension, but they do not have the desired reliability to develop its ultimate tensile strength when uncertainties are considered. Hence, an improved development length requirement is proposed.