Disturbed Stress Field Model Based Non-linear Finite Element Analysis Of Reinforced Concrete

The nonlinear finite element analysis of cracked reinforced concrete has being developed for about 40 years and great success has been achieved. In general, the cracked concrete is treated as an orthotropic material. But up to now, two major problems still exist: the first is, how to formulate a rational stress-strain relation relationship to describe the cracked concrete under combined, and the second is loading conditions and how to utilize these models to get the response of the components and structures with a numerically sound algorithm. These problems have been drawing the attentions of researchers worldwide. In modeling materials under different path of loading, effect of unloading and reloading paths of both concrete and reinforcement, treatment of cracks, and local effect at cracks under cyclic loading are of crucial importance.On the basis of 2-D nonlinear finite element NAP program by Lai Wuqing based on the rotating and smeared crack models proposed in the MCFT(Modified Compression Field Theory), the following work has been carried out in this paper:1. Improvement on the NAP program with more accurate local effect by satisfying crack-check conditions at cracks has been carried out.2. The compression softening is taken into consideration.3. Local shear-slip at cracks is modeled by using DSFM.4. Simulation of tested panels and walls under monolithic and cyclic loading is undertaken.The following achievements have been obtained:1. Importance of crack-check is verified.2. Inclusion of compression softening effect on response of cracked concrete yields more accurate results.3. Simulation of local shear-slip deformation at cracks can improve the accuracy of response of 2-D cracked reinforced concrete.