基于起裂韧度准则的混凝土裂缝黏聚区特性

基于起裂韧度扩展准则和黏聚裂缝模型研究混凝土断裂全过程中的裂缝尖端黏聚区特性;利用不同尺寸的带裂缝三点弯曲梁试件,计算得到了裂缝尖端黏聚区的长度、黏聚力、裂缝张开位移等,并采用现有试验成果和有限元方法计算成果对本文结果进行了验证。分析结果表明:最大黏聚区长度以及峰值时刻对应的临界黏聚区长度随试件尺寸增大而逐渐增大,最大黏聚区长度受拉伸软化曲线影响;裂缝断裂全过程曲线受软化曲线影响较小;当外荷载达到峰值后裂缝张开位移近似为线性分布,黏聚力分布受拉伸软化曲线影响较大。

Characteristics of cohesive zone of concrete cracks based on initial fracture toughness criterion

The characteristics of the cohesive zone at crack tips throughout the fracture process were studied based on the initial fracture toughness(IFT)criterion and cohesive crack model. Single-edge notched beams with different sizes, subjected to three-point bending, were used as specimens, and the length of the cohesive zone at crack tips, the cohesive stress of concrete, and the crack opening displacement(COD)were calculated. The calculated results were verified with the results from tests and the finite element method(FEM). Results show that the maximum and critical lengths of the cohesive zone increase with the size of specimens; the maximum length of the cohesive zone is influenced by the tensile softening curve, while the whole fracture process is slightly affected by the tensile softening curve; after the peak load is reached, the COD is approximately linearly distributed; and the distribution of cohesive stresses depends on the tensile softening curve.