Nonlinear Response And Collapse Analysis Of RC Frame-wall Structures Based On Discrete Element Method

Research on nonlinear response and collapse damage of structure under earthquake is an important subject in structural engineering disciplinary and one of the research hotspots currently. Although several numerical analysis methods have already been put forward by domestic and foreign scholars, they are still difficult to deal with the entire process simulation on the structure from elastic to plastic, small deformation to large deformation and even to collapse perfectly.As a non-continuous numerical analysis method, Discrete element method(DEM) does not require the displacement of coordination between elements, and applies to solving the issues in structural collapse such as non-continuous displacement field, large displacement and large rotation. The discrete element method was firstly developed in geotechnical engineering, and has gradually applied in structural nonlinear seismic response and collapse mechanism analysis. However, the previous model based on DEM is lack of the element model for wall-slab members, so that,they are difficult to analysis the nonlinear response and collapse damage of large complex frame-wall and shear wall structure. Therefore, the accurate simulation of structural nonlinear behavior based on DEM are worth further studying.This paper focuses on the nonlinear performance analysis of RC frame-wall and shear wall structure based on DEM, concrete work is as follows:1.Based on reading a large number of domestic and foreign literature, research status of numerical analysis methods for structural nonlinearity and collapse analysis especially DEM in structural engineering are summarized and reviewed. Moreover, Segment-Multi-Spring theoretical Model based on DEM for beam-column members are studied.2. Multi-spring shell element model suitable for wall-slab structures is proposed. Matrix for coordinate transform of varied local coordinate and constant whole coordinate are established to describe position and shape changes of structures. To avoid the impact of path correlation on results, synchronistic dynamic relaxation method and central difference method are used to do iterative calculations of various loading conditions. Then balance between elements is established.3. Secondary development of the SMS-Collapse program was carried on. Improvement of the pre-processing module using Fortran language and the multi-spring shell element models of wall member was added to the pre-processing module. Database information of PKPM software was studied and conversion program between PKPM and SMS-Collapse program based on Python language was written to realize SMS-Collapse program's fast and accurately parametric modeling.4. Numerical simulation of RC shear wall specimens under low cyclic load has been carried out and compared with experimental test. The result indicates that the multi-spring shell element models are able to accurately simulate nonlinear performance of RC members, and finely describe the history of mechanical behavior on the cross section of RC members. Therefore, the structural analysis model established is reasonable.5. Numerical simulation of reinforced concrete shear wall structure of different axial compression ratios and aspect ratio under low cyclic load has been carried out. The result indicates that the numerical results are in good agreement with the test results. And the multi-spring shell element models in the paper can be applied to different types of nonlinear analysis of shear walls, and has a high accuracy as well.6. This paper has been developed to simulate the failure process of RC shear walls under cyclic lateral loading, and compared with the experiment results. Numerical simulation of the hysteretic curve and the experimental hysteretic curves coincide. It indicates that the multi-spring shell element models can truly and correctly descript the structural reaction in this paper, it will lay a foundation for frame-wall and shear wall structural collapse failure process analysis under earthquake.