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采用外贴应变片方法测定弯曲荷载下裂纹长度的发展,得到荷载及相应弯曲裂纹长度关系(P-a);然后应用粘性裂纹模型,通过比较理论计算的梁的承载力与试验获得的相应裂纹长度时的承载力得到混凝土材料拉应力-裂纹宽度(s-w)关系,并进而得到材料的开裂强度、抗拉强度、断裂能和脆性特征长度等断裂力学参数。基于上述方法,求解3个强度等级的快硬混凝土抗拉软化关系。结果表明,随着混凝土强度的升高裂纹粘聚应力逐渐增大,混凝土材料的开裂强度、抗拉强度、断裂能均逐渐增大;同时,特征长度逐渐减小,说明强度越高混凝土材料越脆。所得到的s-w关系,可用于分析相关混凝土结构的断裂。
The development of crack length under bending load was measured by external strain gauge method, and the relationship between load and corresponding bending crack length (Pa) was obtained. Then, the viscous crack model was used to compare the bearing capacity of the beam and the corresponding crack length The relationship between tensile stress and crack width (SW) of concrete is obtained, and then the fracture mechanics parameters such as crack strength, tensile strength, fracture energy and brittle characteristic length are obtained. Based on the above method, the relationship between tensile strength and softening of fast hardening concrete with three strength grades was solved. The results show that with the increase of concrete strength, the crack cohesion stress gradually increases, and the cracking strength, tensile strength and fracture energy of concrete material increase gradually. At the same time, the characteristic length decreases gradually, indicating that the higher the concrete strength, brittle. The resulting s-w relationship can be used to analyze the fracture of the relevant concrete structure.