Crack Propagation Process of Concrete under Sustained Loading: An Experimental and Numerical Study
Concrete structures in service are frequently subjected to sustained loading, which may lead to crack propagation at high load levels and the subsequent reduction in structural stiffness. Therefore, investigating the crack propagation process is essential for evaluating structural performance. This study investigates the crack propagation process of three-point bending beams under sustained loading through experimental tests and numerical simulations. First, creep fracture tests are conducted under sustained load levels of 0.90, 0.85, 0.80, and 0.75. The results indicate that as the load level increases, the nonlinear characteristics of concrete become more pronounced, the creep fracture lifetime decreases exponentially, and both the crack mouth opening displacement and crack propagation length gradually decrease with increasing sustained load level. Subsequently, numerical simulations are performed to calculate the creep fracture lifetime, crack mouth opening displacement, and crack length under different sustained load levels. In these simulations, the viscoelastic behavior of concrete is represented using a two-element Kelvin chain model, and the decay of cohesive stress in the fracture process zone is described through the tension-softening constitutive model proposed in the previous research. A crack propagation criterion based on initial fracture toughness K Ic ini is employed. The numerical results exhibit good agreement with the experimental results, confirming the validity of the proposed method in predicting the creep fracture behavior of concrete. These findings provide a reference for estimating the creep fracture lifetime of concrete structures under sustained loading.