Cracking in reinforced concrete bent caps

This paper presents the findings from an experimental investigation into the causes of unexpected cracking in reinforced concrete bent caps at outside column locations during service load conditions. Sixteen full-scale bent cap specimens were constructed and tested under quasistatic monotonic loading. The following bent cap parameters were evaluated with regard to their influence on cracking: longitudinal reinforcement stress, size, and spacing; embedment of longitudinal reinforcement near the discontinuous end of the cap; transverse reinforcement detailing and shear strength; critical section for flexure; and side face reinforcement. Cracks were measured and reinforcement strain data were recorded throughout the load history. The experimental program confirmed that flexural crack widths during service loading are directly proportional to the level of stress in the longitudinal reinforcement and that the allowable service stress limit should be lowered to reduce such cracking. In addition, increasing the shear strength of the bent cap led to reduced inclined flexure-shear crack widths.