Effects of Concrete-to-Reinforcement Bond and Loading Conditions on Tension Stiffening

Within the tension zone of a cracked reinforced concrete beam, the intact concrete between adjacent cracks is able to sustain certain level of tensile stresses and contribute to the flexural stiffness of the beam. This tension stiffening effect is of high importance in deflection calculation of concrete beams and can be accounted for in design practice by using a tensile stress block in section analysis. Recently, the authors have employed finite element analysis to evaluate the tension stress fields in cracked concrete beams. Based on the stress field results, tensile stress blocks for practical use in structural design have been formulated. To continue the study, this paper examines the sensitivity of tensile stress block to the concrete-to-reinforcement bond characteristics and to the loading conditions. It is found that the bond characteristics do not have significant effect on the tensile stress block. On the other hand, the loading conditions do significantly affect the tensile stress block. Formulas of stress block parameters are proposed to address the effect of loading conditions.