Engineering Solution for the Uniform Strength of Partially Cracked Concrete

Abstract

Significant computational resources are required to predict the remaining strength from numerical fracture analysis of a jointed plain concrete pavement that contains a partial depth crack. It is, therefore, advantageous when the failure strength can be adequately predicted with an engineering solution. Current engineering or closed-form solutions are based on the elastic effective crack approach with the fracture parameters toughness and critical crack tip opening of concrete. The solutions do not directly consider the effect of the distance to the boundary conditions (restrained slab length) and the cracking process caused by stress softening across the crack. A proposed engineering solution methodology includes these latter variables. The application of the solution is demonstrated on a slab containing a partial depth midslab crack and subjected to in-plane tension. The solution captures the effects of material fracture properties and structural size in terms of crack length and distance from boundary to the crack. The model assumes a bilinear stress–crack width relationship for the fracture process zone. The concrete characteristic length, determined from the fracture energy represented by the first part of the stress–crack width relationship, controls the failure load of a partially cracked concrete slab. A unique master curve between slab strength and crack depth was developed using the results from the numerical analysis. The master curve was verified with results from laboratory testing of large-scale slabs subjected to in-plane tension. The solution methodology can readily be extended to other loading cases.