基于能量法的水环境混凝土疲劳裂缝扩展模型

Fatigue crack propagation model of concrete under water pressure based on energy approach

针对低频疲劳荷载与孔隙水压力的耦合作用,将混凝土疲劳裂缝扩展所消耗的能量分为两部分,一部分由低频疲劳荷载提供,另一部分由孔隙水压力提供,并给出了两部分能量的计算方法。基于能量的可叠加原理,结合混凝土断裂过程中能量释放率的概念,建立了低频疲劳荷载与孔隙水压力耦合作用下混凝土的裂缝扩展模型,并通过试验数据对模型进行了验证。结果表明:当孔隙水压力为0时,模拟曲线与试验数据吻合较好;当孔隙水压力与低频疲劳荷载共同作用时,水压作用会提供闭合裂缝张开时消耗的能量,促进裂缝的扩展,导致裂缝扩展速率增大,且随着孔隙水压力的增大,裂缝扩展速率增加,混凝土疲劳寿命降低。

For the coupled action of low frequency fatigue loading and pore water pressure,the energy for fatigue crack growth of concrete is usually divided into two aspects.The theoretical approach of energy provided by low frequency fatigue loading and pore water pressure can be derived,respectively.Based on the superposition principle of energy approach,the crack propagation model under the coupled action of low frequency fatigue loading and pore water pressure was developed considering the concept of energy release rate during the fracture of concrete.Then,the theoretical results were validated using available experimental data in the literature.The comparisons indicate that the proposed model agrees reasonably well with experimental data when the pore water pressure is ignored.Moreover,it is found that under the combined action of low frequency fatigue loading and pore water pressure,the pore water pressure can provide the energy dissipated by the opening of closed crack to accelerate the crack growth.Moreover,the crack propagation rate increases with the increase of pore water pressure,which results in the reduction of the fatigue life of concrete.