Research On Numerical Simulation Method Of Progressive Collapse Resistance Of 3D RCS Connection Based On Local RBF Collocation Method

Reinforced concrete column-steel beam(RCS)composite structure is a new type of structural system,which can give full play to the respective advantages of the two materials,and is a low-cost and high-efficiency structure.The progressive collapse performance is one of the important properties of the structural system.The progressive collapse involves the deformation and movement of the grid.The grid needs to be updated continuously.The use of traditional grid-like numerical methods may cause accuracy to not meet the requirements of the actual project.The meshless method uses discrete points for interpolation calculations,which does not require high continuity in the computational domain,avoids the memory and time consumption caused by meshing.It provides a new idea for solving scientific and engineering problems.Therefore,the paper conducts the following research:(1)The interpolation principle of the meshless method applied to the spatial node model is described.The system deduces the calculation process of LRBFCM and expresses it as a simple and easy-to-understand discrete matrix form,introduces the idea of domain decomposition method to improve the stability of LRBFCM,and discusses the selection of shape parameters and the way of taking points of the method are discussed,which provides a certain theoretical reference for the solution of the subsequent three-dimensional space RCS beam-column joint problem.(2)The steps to solve the elastoplastic problem using the full-quantity method are listed to provide ideas for programming the LRBFCM.Three numerical examples are given.The results are compared with the COMSOL finite element results to prove the effectiveness of the LRBFCM in solving the elastoplastic problem.The influence of shape parameters on the calculation accuracy is studied,the research shows that the selection of shape parameters is closely related to the distance between discrete points.If the parameter is too large,the influence of the distance between discrete points on the calculation results will be ignored.If the shape parameter is too small,it will lead to the approximate function(MQ)directly ignore the influence of this factor;when the distance between the shape parameter and the discrete point is determined,the number of discrete points in the local subdomain can be appropriately increased to improve the calculation accuracy.(3)The LRBFCM was used to calculate the beam-column joints of the spatial RCS composite structure,the results were compared with the finite element,draw the displacement load curve,analyze the force mechanism of different joint forms.The research found that the results calculated by LRBFCM meet the requirements of engineering errors and can be applied to actual engineering calculations,providing a new solution for solving engineering problems.Under the same loading conditions,the vertical displacement of column-through joints is significantly greater than beam-through joints,and beam-through joints have better ductility.Therefore,the progressive collapse resistance of beam-through joints is better than that of column-through joints.The research in this paper is based on the National Natural Science Foundation of China(51768044).It uses independent programming instead of finite element commercial software to provide a new research method for the progressive collapse of RCS composite structure connection.