Cracking and tension zone behaviour in RC flexural members

This paper presents the results of an extensive programme of research carried out jointly at the University of Leeds and the University of Durham to clarify various aspects of cracking behaviour particularly in the tension zones of flexural members. The results show that concrete cover is the only parameter affecting the transfer length at load levels close to cracking and up to service load. An attempt has also been made to show the bond mechanism at the bar - concrete interface using the technique of ink injection. Unfortunately, this technique failed to reveal internal cracks between two major cracks when the stress in the reinforcement was increased up to approximately 200 MPa; whether this was attributed to their absence or to faults in the testing procedure was unclear. The current paper also proposes an empirical formula to predict the transfer length in slabs. The input data required are more simple and convenient to collect than using a crack width microscope and the predictions from the formula are just as accurate.