Controlling the crack width of flexural RC members

摘要

Reinforced concrete (RC) structures built using high strength deformed bars and designed using limit state design method were found to have larger crack widths. To control these crack widths and to enhance durability, different codes prescribe limiting crack widths based on the environment in which the structure exists. The latest revision of the Indian code stresses the importance of durability and has introduced formulae to calculate the crack widths. Unfortunately, the formulae given in the Indian code are complex and are seldom used in practice. A similar approach was used in the American code till 1999. However, recent research has found that there is no correlation between corrosion and crack widths. Also, there was a large scatter in the measured crack widths even in controlled laboratory experiments. Hence, a simple formula, involving the clear cover and calculated stress in reinforcement at service load has been included in the latest revision of the ACI code. A similar formula which also takes into account the effect of epoxy coating on reinforcement is suggested for the Indian code. Discussions on controlling the flexural cracking in the flanges of T-beams and side face reinforcement of large reinforced concrete beams are also included in the paper. The author highlights the need of introducing a simple formula for controlling crack widths in Indian codes on similar lines of the ACI code.