Study On The Actual Force Of Main Columns And Beams In RC Frame With The Influence Of Cast-in-place Slab In Consideration

In the Code for Seismic Design of Buildings(GB50011-2010),the "strong column coefficient" is used to achieve the "Strong Beam Weak Column" design guidelines,when designed,the column end bending moment is enlarged relative to the beam end's,but in the actual earthquake damage,the major failure mode of frame structures are "Strong Beam Weak Column",which is on the contrary of the code"Strong Column Weak Beam".One of the main reason is that the enhancement effect of reinforcement in cast-in-place slab on the beam bending moment capacity,in addition,the existence of the cast-in-place slab may also have an effect on the actual force in the frame beam and the column,which make the axial force of the beam and the torque at the end of the column can not be neglected,then the damage form of the beam-column joints will be affected,but when carried out in accordance with the existing methods for structure design,the axial force of the beam and the torque at the end of the column is ignored.In order to confirm how slab influence the actual force of beams and columns,and to study how the actual force of beams and columns effect on the damage form of structure,the following studies are proceed in this paper:(1)A reinforced concrete frame of 3 floors and 3×3 cross is designed based on the software of PKPM,and five numerical analysis models are built using the finite element method software of ABAQUS,whose one or more floors are removed in the different positions of bottom floor.The stress curve of each beam-column joint is investigated to analysis how the slab affect on the bending moment capacity of beam and the failure mode of the beam-column joints.(2)Seven models of the reinforced concrete frame structure are analyzed using ABAQUS,whose slabs on the same floor but in different positions or in the same position of different floors are removed.The curves of axial force of the frame beam and the orthogonal beam are analyzed to research the influence of slab to the rebar stress of the frame beam and the orthogonal beam.(3)Seven models of the reinforced concrete frame structure are analyzed using ABAQUS,whose slabs on the same floor but in different positions or in the same position of different floors are removed,and the relationship of the torque at the end of the column and the lateral is analyzed to illustrate the rebar force of the columns.(4)The axial force of the frame beams are considered to adjust the reinforcement,and ten numerical analysis models of X1-X10 are built and simulated by ABAQUS,compared with the model M1-M10,which are based on the existing internal force calculation method that neglects the axial force of frame beam,the reinforcement stress curve of the beam and column and the curve of the torque at the end of the column are compared to illustrate how the axial force of the frame beams impact on the failure mode of the beam-column joints.The analysis results indicate that the "Strong Column Weak Beam" will be more easily to achieve when the axial force of the beam is considered.In the process of structural design,the axial force of the frame beam should be considered reasonably.