TIME-DEPENDENT BEHAVIOR OF CRACKED CONCRETE BEAMS UNDER SUSTAINED LOADING

Under sustained loading, the propagation of cracks in concrete is assumed to be related to the elastic deformation, material parameters and time. Based on the fictitious crack model (FCM), a finite element method is proposed to explain the behavior of cracks in time using current constitutive relations to approximate the time-dependent crack strain. Experiments have been performed on small concrete specimens to determine the cracking strain and to validate the finite element model. For flexural cracks, a creep coefficient model is adopted for bulk creep and a cracking strain rate based on test results is employed. For shear cracks fracture mode II is considered as well. The development of concrete strength in time is taken into account. The model is applied to predict the behavior of a cracked concrete beam subjected to sustained loading. Finally a comparison is made between the results of different approaches.

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