| Static and dynamic analyses of concrete failure based on fracture mechanics were conducted using crack-line wedge-loaded, double cantilever beam (CLWL-DCB) and edge-cracked, three point bend specimens under Mode I loading conditions, aimed at developing a mathematical model which describes the tensile failure process of concrete materials at the macro-level.; The fracture process zone associated with a stably growing crack in concrete was determined by a hybrid experimental-numerical technique where a crack closure stress versus crack opening displacement (COD) relation of a finite element model of the specimen was optimized to fit the COD data, obtained by Moire interferometry with real reference grating, and other experimental measurements.; For the first time, the crack closure stress versus COD relation of a fracture process zone in concrete was determined directly and was found to be similar to those obtained by others using inverse procedures. The crack closure stress versus COD relation for the two CLWL-DCB and edge-cracked, three point bend specimens were identical thus implying that this relation is a specimen-independent but material-dependent constitutive relation.; The above static constitutive relation, with modifications to account for the differences in tensile strengths and aggregate sizes, were used to simulate the recorded dynamic crack propagation in large scale, impacted three point bend specimens (unnotched) by Mindess and the Charpy type impact tests by Shah. In both cases, dynamic finite element modeling with the adjusted constitutive equations for the fracture process zones simulated the measured crack propagation histories within the experimental accuracies. |
