CONTROLLING CRACK WIDTHS IN WALLS RESTRAINED AT THEIR BASE AND ENDS

Abstract

Following casting, concrete cracks if early-age thermal (EAT) and long-term (LT) shrinkage movement is restrained. Crack control is of particular importance in walls which rely solely on concrete for water tightness, such as retaining walls and water resisting tanks. It is well established that the cracking behaviour of end restrained members is very different from that of edge restrained walls. For this reason, both restraint types are considered separately in literature and in codes of practice such as Eurocode 2 (EN 1992). In reality, combined edge and end restraint is present in many reinforced concrete (RC) structures. In the absence of design recommendations for combined restraint, U.K. engineers commonly design crack control reinforcement for end restraint as it is the worst case. In the authors’ opinion, this is wasteful as it leads to the provision of unnecessary reinforcement. To this end, an experimental programme was conducted to investigate cracking in RC walls with combined base and end restraint. The measured and calculated crack widths are compared with the predictions of EN 1992 for edge and end restraint. The results suggest that crack widths in walls with combined edge and end restraint can be calculated with the EN 1992 equations for cracking in edge restrained walls.