Numerical evaluation of the non-linear behaviour of cracked RC members under variable-amplitude cyclic loading

The accurate calculation of the non-linear behaviour of reinforced concrete (RC) members under cyclic loading requires that realistic constitutive models are employed to describe the material responses and robust numerical methods are used to achieve the solution. Given the complex nature of the mechanical behaviour of RC members after cracking, widely accepted numerical methods are still not available to predict the service-life performance of structures subjected to important cyclic loads. This paper discusses the adequacy of available constitutive models, in the context of the numerical calculations envisaged in this work. Then, the adopted numerical methodology is described. The specificities of small reloading steps and related convergence difficulties are discussed in detail and a strategy is introduced to overcome such difficulties. The validity of the presented methodology is confirmed by comparing the numerical predictions against experimental results reported in the bibliography. The variability of the calculation results is also addressed. It can be concluded that the proposed numerical procedure provides a good description of the mechanical behaviour of cracked RC members upon unloading and reloading steps.