Cracking in walls with combined base and end restraint

Abstract

Restraint of early-age thermal and long-term shrinkage strain can cause cracking in reinforced concrete members. Eurocode 2 provides guidance on the design of crack control reinforcement in reinforced concrete elements with base (edge) and end restraint but not combined base and end restraint which commonly occurs. The paper describes an experimental programme, which was conducted to investigate early-age and long-term shrinkage cracking in reinforced concrete walls with combined base and end restraint. The main variables in the test programme were concrete cover and reinforcement ratio. Early-age cracking is simulated with nonlinear finite element analysis, which is shown to capture the observed behaviour adequately. Eurocode 2 gives reasonable estimates of long-term crack widths in the tested walls if edge restraint is assumed but significantly overestimates crack widths if the worst case of end restraint is assumed.

Investigation of the influence of external edge restraint on reinforced concrete walls

“…An example of a situation where both forms of restraint may exist can be found by considering a new section of concrete cast between two pre-existing concrete wall sections and onto a pre-existing concrete base [9]. Whilst a greater understanding of edge restraint in isolation is being gained [10,11], the optimum problem constituted by a combination of the two restraints is still little understood. Forth [12] suggested that in such a scenario, both types of restraint will dominate in different parts of the wall.…”