New Double-K Criterion for Crack Propagation in Quasi-Brittle Fracture under Moderate Dynamic Loading

摘要

INTRODUCTION Moderate dynamic loadings refer to the loadings within the strain rate regime of 10~(-4)/s-10~0/s. These loadings may result from the earthquakes, the impacts of water and the wind etc. For the structures like buildings, bridges, dams, nuclear containment vessels and ocean platforms, these moderate dynamic loadings are more likely to occur than the loadings at very high loading rates. However, the damage caused to the structures by the former may not be smaller. Unfortunately, relative few dedicated study is available for the moderate dynamic fracture of quasi-brittle materials like concrete, especially in the aspects of fracture criterion establishing. As a simple, convenient and indirectly measured method, the double-K criterion is already utilized to the assessment of crack security and the structure design for the dams under quasi-static loading condition, yet more research in the moderate dynamic field is required to shed light on the matters of rate sensitivity of the quasi-brittle fracture. Therefore, an attempt to a new double-K criterion which takes the loading rate effect into account is made in this paper.