| Prefabricated concrete building has the remarkable advantages of high construction efficiency,less consumption of building materials and short construction period.China vigorously advocates the development of building industrialization,and the research on prefabricated building has also rapidly developed into a frontier research field.Prefabricated concrete frame structure is one of the most widely used prefabricated structure systems.The research on prefabricated concrete frame structure mainly focuses on the joints of precast beams and columns,because the reliability of joints is the key to determine the overall mechanical performance of prefabricated concrete frame structure.With the rapid development of computer technology,the simulation analysis of prefabricated concrete structure combined with finite element method has become an important means of auxiliary calculation research.In this paper,the finite element program ABAQUS will be used to carry out a series of numerical simulation research around the dressed frame structure.（1）A refined finite element model is established for the post cast integral joint of composite beam and precast column.First of all,based on the test of a joint,this paper establishes the fine geometric model of the joint with the finite element software ABAQUS,and focuses on the mechanical properties of the interface between the new and old concrete,the large-diameter longitudinal bar and the steel sleeve and the concrete contact surface of the prefabricated member,and establishes the fine finite element model of the joint Results the average difference of bearing capacity,strength degradation coefficient,stiffness degradation coefficient,energy dissipation coefficient and displacement ductility coefficient is no more than 5.3%,6.7%,9.1%,6.7% and8.44%,respectively.The numerical simulation results are in good agreement with the experimental results,which shows that the refined finite element model of the joint can simulate the test better The results show that the failure mode and mechanical performance of the joint are reasonable and effective.Secondly,through the parametric analysis of the concrete strength,longitudinal reinforcement ratio and axial compression ratio in the joint area,the results show that on the basis that the section reinforcement of the joint meets the design requirements of the specification,improving the longitudinal reinforcement ratio and concrete strength of the joint is the most effective way to improve the bearing capacity of the joint.Finally,on the basis of the refined finite element model of the joint,in order to improve the bearing capacity of the precast beam end,the design and transformation suggestions of the joint with short anchor bars at the beam end are put forward.（2）It is very important to study the mechanical performance and reliability of key joints.However,the failure of a complete structure in practice is a complex process.The root of structural failure lies in some local components or key components,and the final failure is reflected in the macro level of the whole structure.If in the actual engineering design,we use the refined finite element modeling analysis of the whole structure,it will consume a lot of computing time and resources.How to find a balance between the overall calculation of macro scale structure and the small-scale fine analysis of local key components,and at the same time,consider the calculation efficiency,accuracy and rationality.One of the effective ways to solve this problem is to introduce the structural multi-scale analysis method into the finite element modeling analysis of the assembled integral frame structure.In this paper,a fabricated monolithic reinforced concrete frame structure test is taken as an example,and the multi-scale interface connection is realized by using the MPC multi-point constraint mode of the finite element program ABAQUS,and the multi-scale finite element model of the structure is established.At the same time,the refined solid element model and the macro beam element model are established as a comparative reference.The results show that: the natural frequencies of the first three vibration modes calculated by the three models are relatively close,and the maximum difference of the natural frequencies of the first three vibration modes of the multi-scale model is not more than8.9%.The skeleton curves of the three models are basically consistent with the test results,and the relative errors between the calculated bearing capacity and the test values are 7.71%,7.34% and 7.32% respectively.It also proves the validity and rationality of the multi-scale model of prefabricated frame structure.In addition,the number of refined entity units is 47266,and the CPU operation time is 22107 s,The number of macro beam element model is 1904 and CPU operation time is 715 s,while the number of multi-scale model is 9881 and CPU operation time is 1807 s.It is obvious that multi-scale model has comprehensive advantages in consuming computer resources and calculation time,which provides theoretical basis for engineering design and structural analysis of prefabricated structure.（3）A multi-scale model combining the refined finite element model of local key nodes with the overall model of macro scale structure is established for time history analysis of an engineering example.Firstly,the local key parts of the whole structure are determined by using the efficiency of the macro beam element model,and then the multi-scale model of the structure is connected at the multi-scale interface by using the MPC multi-point constraint method.Through the dynamic time history analysis of the multi-scale model,it is found that the multi-scale model only takes 6783.3s to complete the calculation and analysis of the overall seismic performance of the structure and the refined solid element model of the key nodes.This will greatly improve the calculation and analysis efficiency of prefabricated structure,and also provide new modeling and analysis ideas for the engineering design calculation,engineering seismic research,engineering seismic reinforcement and transformation of prefabricated structure. |
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