Study On The Dynamic Responses Of Monolithic Precast RC Frame Structures Considering Slab Effects

At present,China is vigorously promoting prefabricated buildings,and the application of prefabricated structures in daily buildings is more and more extensive.Compared with cast-in-situ structures,prefabricated structures have common problems such as weak joints and poor integrity.As the main structural form of fabricated structure,the research on the collapse resistance of fabricated frame structure is becoming more and more important.As an important force transmission component of frame structure,floor often plays an important role.Considering the influence of floor in progressive collapse resistance,the progressive collapse design of structure can be better carried out.In this paper,five cast-in-place and monolithic precast substructure tests are simulated based on Open SEES finite element platform.The correctness of the simulation method for reinforced concrete substructure is verified.At the same time,the three-dimensional cast-in-place frame model is established and analyzed by nonlinear dynamic analysis method.The effectiveness of the nonlinear dynamic analysis method based on Open SEES is verified by comparing the dynamic response law in this paper with the existing literature.On the basis of the correct simulation method and analysis method,the three-dimensional monolithic precast frame model is established and the nonlinear dynamic analysis is carried out.The dynamic response is compared with the dynamic response of the cast-in-situ frame to study the dynamic response of different forms of frames.Finally,the models of monolithic precast frame with floor and cast-in-place frame with floor are established to study the dynamic response of monolithic precast frame considering the influence of floor and the progressive collapse resistance of floor in monolithic precast frame.The importance of floor in different forms of frame is judged by comparing the role of floor in monolithic precast frame and cast-in-place frame.The main research contents and results are as follows :（1）The design of five cast-in-situ and monolithic precast substructure tests is introduced.Appropriate elements and materials are selected by Open SEES finite element software to model and simulate the five substructure tests,and the test results and simulation results are compared.It can be seen from the comparison results that the element and material constitutive selected in this paper can better simulate the progressive collapse resistance of reinforced concrete substructure,the Joint2 D element can better simulate the shear behavior of fabricated joints,and the T-shaped fiber cross-section beam can better simulate the contribution of floor to the structural bearing capacity.（2）Based on the above beam-column substructure simulation,a three-dimensional cast-in-place frame is established,and the method of modal analysis and period calculation of the frame combined with ETABS and Open SEES is introduced.On the basis of the above method,the nonlinear dynamic analysis of the cast-in-situ three-dimensional frame is carried out.Different positions and time of column removal are set.The vertical displacement of the failure column node and the internal force of the key beam are analyzed.The dynamic response of the three-dimensional cast-in-situ frame is analyzed,and the rationality of the nonlinear dynamic analysis method based on the Open SEES platform is verified.（3）The three-dimensional monolithic precast frame is established on the basis of cast-in-situ frame by using the Joint3 D unit.The nonlinear dynamic analysis of the three-dimensional monolithic precast frame is also carried out to study the dynamic response of the three-dimensional monolithic precast frame.The dynamic response of monolithic precast frame and cast-in-place frame is compared,and the dynamic response of different forms of frame is analyzed.It can be seen from the analysis results that in the monolithic precast frame,the corner column is the most sensitive component,which is most likely to cause progressive collapse.When the precast concrete strength of the fabricated frame is the same as that of the cast-in-situ frame,and the strength of the post-cast concrete is greater than that of the precast concrete,the dynamic response of the monolithic precast frame under different column removal positions is weaker than that of the cast-in-situ frame.However,other factors need to be considered for the anti-progressive collapse ability of the monolithic precast frame and the cast-in-situ frame under and further research is needed in the future.In addition,the structural type of the frame has little effect on the dynamic amplification coefficient of the structure.（4）Establishing three-dimensional cast-in-place frame with floor and three-dimensional integral frame with floor assembly.At the same time,the nonlinear dynamic analysis of the frame is carried out to study the dynamic response of the three-dimensional assembly integral frame considering the influence of the floor slab.The dynamic response of assembled monolithic frame with or without floor slab is compared,and the role of floor slab in assembled monolithic frame is analyzed.In the modeling process,in order to consider the influence of floor,a simplified floor simulation method is established by using T-shaped and L-shaped fiber beam sections to simulate the bending effect of floor and the tensile effect of beam-net template floor.The three-dimensional cast-in-place frame with floor is established,and the influence of floor on structural dynamic response in cast-in-place frame and assembly integral frame is compared to analyze the importance of floor in different forms of frame.The analysis results show that the column removal time has a significant impact on the assembled monolithic frame with floor slab.The shorter the column removal time is,the more obvious the structural dynamic response is.Floor slab can greatly improve the collapse resistance of assembled monolithic frame and reduce the dynamic response after local column failure.In the assembled monolithic frame,the role and importance of floor are higher than those of cast-in-situ frame to a certain extent,and the influence of floor should be considered as far as possible in the structural design.