Nonlinear Finite Element Analysis Of Reinforced Concrete Direct-shear Tests

The nonlinear finite element method is an effective way for complex stress analysis of concrete structure. The non-linear performance of the concrete is caused by sudden changes in stress and reduction of stiffness in surrounding concrete which owe to the cracks. And the shear failure of direct-shear test is analogous to which of beams, a main crack comes into being at the shear plane, resulting in a strong disturbance on the displacement field near the crack before the damage. In order to investigate the suitability of smeared crack model for the analysis of such problems, based on finite element program DIANA, three different smeared crack models, total strain rotating crack model, total strain fixed crack model and multi-directional fixed crack model, are supplied to analyse the direct-shear tests without pre-splitting which had been carried out recently in Dalian University of Technology. We discussed the feasibility about whether the smeared crack model apply to the problems where the damage is brought by such one or few main cracks, and also the comparison of calculation results among the rotating crack model, the fixed crack model and the multi-directional fixed crack model is done. This study provides a new way for the non-linear numerical analysis of shear transfer performance in reinforced, unreinforced and plain cracked concrete.Based on the verified results of the finite element model of concrete, we studied the influence of the shear plane dimensional and the reinforcement ratio on the shear transfer properties of cracked concrete combining the experimental data using the finite element analysis software DIANA. And after we improved the loading method of the direct-shear test and introduced the confined concrete concept, the height and width of shear plane on the shear transfer properties of reinforced and unreinforced test specimens were considered respectively through 30 group theoretical calculations. We get that the ultimate shear stress of the shear plane is mainly dependent with the height of the shear plane, and the width of the crack surface has little effect on the ultimate shear stress of the shear plane. The shear strength of the structure will be improved effectually if the reinforcement ratio of the shear plane is added propely.