Nonlinear Finite Element Analysis Research Of Reinforced Concrete In Multiple Box Culvert

The nonlinear stress-strain relationship and the cracking of concrete are importantresearch domains of the nonlinear response of reinforced concrete structure with loadsapplied. In this dissertation, three constitutive relationships, the linear elasticity model,the multiple linear isotropic hardening model and Drucker-Prager model, and onefailure criterion, the modified Willam-Warnke model with five parameters, areintroduced to describe the nonlinearity of the reinforced concrete multiple box culvert(RCMBC), which is one of the pipes used in the Tianjin main line of the South-to-northwater transfers project. In the same time, the cracking behavior of RCMBC is simulatedby the way of applying the RC smeared orthogonal fixed crack model to the analysis. Inthe course of research, the ANSYS software and its element SOLID65 involved areemployed as the tools of modeling, meshing, and computing. The conclusion is asfollows:(1)In the effect of the RCMBC normal water pressure, the tube concrete stressenvironment is a multiaxial tensile stress state and multiaxial tensile-compressive stressstate with a larger principal tensile stress. With the ascent of the water pressure, the tubeconcrete could be failure and there are cracks one after the other in the points which isthe outer bottom fillet surfaces of two side culvert, the outer top fillet surfaces of twoside culvert, the outside surface of middle culvert bottom board, and the outside middlesurfaces of two flank wall. The cracks appear firstly at the plane of weakness in adirection normal to the σ1 and spread slowly. Subsequently, in the every area ofcracking, the first principal stress is declined with the increment of strain so as toeliminate the probability of cracking in another direction.(2)The tube concrete of the RCMBC has a brittle cracking when the tensile stressreaches the failure surface. Therefore, the stress-strain relationship of concrete beforethe cracking is linear, which has a lower sensibility to using different constitutiverelationship in the model, in the same words, the prediction of the cracking area andcracking stress has a little difference applying the different RC constitutive model.When the linear elasticity model is implemented, the tensile stress in the subsequentcracking area could be evaluated incorrectly because of the effect relating to the stresstransferring in the first cracking area. As the elastic-perfectly plastic material model, theDrucker-Prager model could be improper to predict the cracking stress of the RCMBC,which should be implemented according to the failure criterion defined by the principalstrains.