Research On Mechanical Behavior Of Steel Frames Composed By Integral Composite Beams With End-plate Connections

Based on the verified finite element model of integral composite beam,the mechanical behavior and failure process of the composite beam under cyclic load were discussed.Then,the differences of mechanical behavior of integral composite beams and the traditional end plate connectors under cyclic loading were discussed,The parametric analysis of seven integral composite beam models was carried out and the key factors influencing mechanical behavior of integral composite beam were discussed,The variation parameters include the steel beam flange with or without stiffener,diameter of slab reinforcement and width of steel beam lower flange.Finally,dynamic elastic-plastic time history analysis was carried out respectively for three different steel frames of integral composite steel frame with integral composite beam,traditional end-plate steel frame and steel moment frame.And the performance indexes such as natural vibration period,top displacement,base shear force,the maximum inter-story displacement angle,the component stress nephograms and damage nephograms of steel frame structure were compared and analyzed,and the seismic performance of integral composite steel frame is evaluated to provide theoretical basis for its engineering design and application.Through research,this paper gives us some conclusions as follows:(1)Similar to the traditional composite beam,the negative moment bearing capacity of integral composite beam is obviously lower than the positive moment bearing capacity.In cyclic loading,the bearing capacity of integral composite beam in positive and negative directions is higher than that of traditional end-plate composite beam.(2)The bearing capacity of the integral composite beam with stiffener is obviously higher than that without stiffener.Increasing the diameter of slab reinforcement can significantly improve the bearing capacity of the composite beam under negative bending moment,and contribute to the bearing capacity under positive bending moment,but the amplitude is unconspicuous.By increasing the width of the lower flange of the steel beam,the material distribution of the integral composite beam tends to be reasonable.The bearing capacity per volume of integral composite beam is proportional to the width of lower flange of steel beam,in other words,the larger the width,the higher the bearing capacity per volume.(3)The integral composite beam can effectively increase the overall stiffness of the frame and reduce the natural vibration period of the structure.The peak value of top displacement,the peak value of base shear force and the maximum inter-storey displacement angle of the integral composite steel frame are between the end-plate steel frame and the rigid steel moment frame,the specific difference is related to the type of seismic wave and seismic intensity.(4)Compared with the end plate steel frame,the stress at the end of the column near the joint area of the integral composite steel frame under strong earthquake will be larger,however,the stress on the upper flange of the steel beam at the corresponding position will be obviously reduced,which is related to the effective transfer of load of the floor reinforcement in the beam width range.Among the three kinds of frames,the joint area of rigid steel frame is the most unfavorable.(5)The integral composite beam can give full play to the bearing effect of the flange concrete,and it can keep the effectiveness of the composite effect in the whole process of the steel frame.