中文摘要：

采用中央带穿透裂缝的立方体劈拉试件几何形式,本文研究了应变率对混凝土双K断裂韧度的影响。试验采用的应变率范围为10-5/s-10-2/s。结果表明：双K断裂计算理论可由拟静态进一步拓展到地震加载率;随应变率增加,起裂断裂韧度线性增加,失稳断裂韧度先增加后保持不变;应变率不高于10-3/s时,高应变率作用下的试件会产生较大的临界裂缝扩展长度,临界裂缝扩展率较为缓慢,但应变率高于10-3/s时,临界裂缝扩展长度反而减小,临界裂缝扩展率呈指数迅速增加。最后,引入名义起裂强度率和临界裂缝扩展率两参数分别建立了起裂断裂韧度和失稳断裂韧度的率相关模型。

英文摘要：

This paper presents a study on the effects of loading rate on double-K fracture toughness usingcentral-notched split-tension cube geometry. Fracture tests were carried out under four different strain load-ing rates varying from 10- 5/s to 10- 2/s. The results show that double-K fracture calculation theory,devel-oped previously for quasi-static strain loading rate,can be further extended to seismic loading rate. It wasalso shown that,as strain loading rate increases,the initiation fracture toughness lineally increases but theunstable fracture toughness first increases then maintains a nearly invariant trend. In the case of strain load-ing rate no more than 10- 3/s,specimens with higher strain loading rate presented a bigger critical crackpropagation Δac and slower critical crack propagation rate. However,in the case of strain loading rate great-er than 10-3/s,critical crack propagation Δac reduced for specimens with higher strain loading rate and criti-cal crack propagation rate sharply increased. Subsequently,two models to predict the influence of the load-ing rates on the initiation fracture toughness and unstable fracture toughness were proposed by introducingthe nominal cracking strength rate and critical crack propagation rate,respecitively.