Full-range nonlinear analysis of fatigue behaviors of reinforced concrete structures by finite element method

The offshore reinforced concrete structures are always subject to cyclic load,such as wave load. In this paper a new finite element analysis model is developed to analyze the stress and strain state of reinforced concrete structures including offshore concrete structures, subject to any number of the cyclic load. On the basis of the analysis of the experimental data, this model simplifies the number of cycles-total cyclic strain curve of concrete as three straight line segments, and it is assumed that the stress-strain curves of different cycles in each segment are the same, thus the elastoplastic analysis is only needed for the first cycle of each segment, and the stress or strain corresponding to any number of cycles can be obtained by superposition of stress or strain obtained by the above elastoplastic analysis based on the cyclic numbers in each segment. This model spends less computer time, and can obtain the stress and strain states of the structures after any number of cycles. The endochronic-damage and ideal elastoplastic constitutive models are used for concrete and steel bars respectively. The reinforced concrete slabs of offshore concrete platform subject to cyclic loading are experimented and analyzed by the finite element method based on the model proposed in this paper. The results between the experiment and the finite element analysis are in good agreement, which demonstrates the validity and accuracy of the proposed model.