Compression Fracture and Size Effect in High-Strength Concretes

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9713944 Bazant The fracture mechanics of concrete has progressed greatly, but only for tensile fracture, which is essentially a uniaxial phenomenon. The fracture mechanics of compression fracture, which is a triaxial phenomenon, is essentially unavailable. The present proposal, involving both theoretical and experimental studies, attempts to fill this gap. The theoretical program involves: (1) energy-based mathematical model for the propagation of a band of axial splitting crack (with internal buckling of microcracked material); (2) asymptotic analysis of size effect and shape effect, leading to simple `asymptotic-matching' formulas; (3) formulation of size-effect method for deternining compression fracture characteristics; (4) generalization of the existing microplane model for damage in compression, with consideration of the effect of time or loading rate; and (5) application to the analysis of explosive failure of high-strength concrete columns or walls subjected to fire. The experimental program, designed to verify and calibrate the theory, involves: (1) size-effect tests of double- cantilever fracture specimens with compression-tension loading; (2) size effect tests of compression fracture of cylindrical specimens with small or large notches; and (3) tests of the influence of rate or time. ***