中文摘要：

本文基于损伤耗散能与断裂耗散能等效原理,并假设极限应变服从对数正态分布,建立了混凝土的微弹簧随机损伤模型,进一步给出了混凝土裂缝黏聚律的求解方法。依据所提方法,分别获得了骨料最大粒径dmax依次为80 mm和40 mm的大坝混凝土和湿筛混凝土的黏聚律的具体表达式。基于求解出的黏聚律,分别模拟了大坝和湿筛混凝土的带切口三点弯曲梁裂缝扩展全过程,并将计算得到的荷载-裂缝口张开位移的曲线与试验曲线进行了比较,两者吻合良好,从而验证了模型与求解方法的合理性与有效性。进一步采用建立的模型与方法分析了大坝混凝土和湿筛混凝土材料特征高度的合理取值范围,结果表明：对于本文计算所用的大坝混凝土和湿筛混凝土试件,其材料特征高度值可取6-10倍骨料最大粒径dmax。

英文摘要：

Based on energy consumption equivalence between damage and fracture,a micro-spring stochas-tic damage model was established with the assumption that the micro-spring failure strain is lognormal dis-tribution and further the method of constructing the cohesive law of concrete was studied.The specific ex-pressions of the cohesive laws of dam concrete（dmax is 80mm） and sieved concrete（dmax is 40mm） were ob-tained respectively by this method.Then the obtained cohesive laws were used to simulate the crack propa-gation process of three-point bending notched beams of dam concrete and sieved concrete respectively.Then the P-CMOD curves obtained from calculation were compared with the available experiment data,indi-cating a good agreement,which show the rationality and the effectiveness of the model and the calculationmethod presented in this paper.The characteristic lengths of the dam-concrete and wet-screening concretewere studied using this model and calculation method.The results show that,for the concrete investigatedin this paper,the characteristic lengths are advised to be 6 to 10 times than the maximum aggregate size.