Research On Performance And Design Method Of Assembled RCS Composite Frame Structure To Resist Progressive Collapse

Assembled RCS composite frame structure is composed of prefabricated reinforced concrete column and steel beam.Due to the particularity of beam column joints,its progressive collapse resistance performance and design method are different from concrete frame structure and steel frame structure.Scholars at home and abroad mainly focus on the progressive collapse resistance of frame beams connected with the initial failure columns,while the progressive collapse resistance of other frame columns adjacent to the initial failure columns is not involved.In view of the above problems,the main research contents and conclusions of this paper are as follows:(1)This paper introduces and compares the design methods and analysis methods of progressive collapse resistance at home and abroad.(2)The finite element software SAP2000 is used to analyze the mechanical performance of the residual structure of the prefabricated RCS composite frame structure house designed according to the current code in the seismic fortification area of 6,7 and 8 degrees in China under the failure conditions of corner column,long side middle column and internal column on the first floor.The results show that when a frame column in the ground floor fails,the original load of the column is mainly distributed to the adjacent frame column,and the closer the frame column is to the column,the more the axial force is distributed.Under the above conditions,the bearing capacity of individual columns of the fabricated RCS composite frame with 6and 7 degree fortification intensity does not meet the design requirements of progressive collapse,and there is a risk of progressive collapse;under 8 degree fortification intensity,the bearing capacity of each column meets the requirements.(3)When the beam column joint is semi-rigid,the change rule of the axial force on the other columns is the same as that of the ideal rigid joint under the above conditions.The value of the rotational stiffness of the beam column joint has little effect on the change of the axial force of the column,but the weakening of the rotational stiffness of the beam column joint will reduce the bending moment at the end of the column adjacent to the failed column,which can reduce the risk of eccentric compression failure of the column Insurance.(4)From the perspective of the bearing capacity of frame columns,the order of the risk of progressive collapse caused by the initial failure of columns at different positions in the ground floor is as follows: remove the long side middle column >remove the internal column > remove the corner column,which has nothing to do with the rotational stiffness of beam column joints.(5)The nonlinear dynamic method is used to analyze the above model,and the influence of the rotational stiffness of beam column joints on its dynamic effect is explored.The results show that the semi-rigid joints will delay the time when the internal force of each member and the displacement of the top of the failed column reach the maximum value and stability.The smaller the rotational stiffness of the beam column joint is,the larger the displacement of the top of the failed column is,and the larger the dynamic amplification factor is,with the maximum value of 1.91.The dynamic amplification factor of 2.0 in Chinese code is suitable for this structural system.(6)According to the anti progressive collapse characteristics of the fabricated RCS composite frame structure,combined with the existing research results,some suggestions on the anti progressive collapse design of the structure system are put forward.