Theory and Experiments on the Behaviour of Cracks in Concrete Subjected to Sustained Shear Loading

摘要

There is a lack of information about the behavior of cracked concrete subjected to in-plane sustained shear loading. This subject is the aim of the present study. A short literature survey discusses the basic mechanisms of shear transfer across a crack, viz. interlocking of the opposing crack halves due to protruding irregularities and dowel action by the embedded reinforcing bars that cross the shear plane. The combined mechanism of the short-term tests is significantly affected by the concrete compressive strength, the steel yield stress of the bars and by the restraint of the crack. Next, tests were conducted on 46 push-off specimens each provided with a central crack. The recorded instantaneous and time-dependent displacements have been mathematically represented as functions of the experimental parameters. Generally, a highly non-linear response occurred with respect to the concrete grade and the adjusted shear stress level. Supplementary research focused on microscopic observations of the dowel and on the restraint stiffness of the crack plane, measured by means of strain gages.