The Mechanical Behavior And Plastic Analysis On New Fuse Substructure Of Steel Structure

Energy dissipation beam is the key elements to improve the seismic performance of steel frames,and by adopting replaceable energy dissipation beam,the post-earthquake maintenance cost of the structure can be reduced.The energy dissipation beam of conventional steel frames is usually scattered throughout the structure,which cannot effectively concentrate the inelastic deformation of the structure on the energy dissipation beam during earthquake action and it causes extensive post-earthquake repair work.In order to solve the above problems,the energy dissipating beam are separated from the main bearing members and arranged centrally in the form of substructures to facilitate centralized replacement after earthquakes to reduce maintenance costs.Base on that,a new composite steel frame with fuse substructure system is proposed.ABAQUS and SAP2000 finite element analysis software was used to analyze the mechanical behavior of single-layer fuse substructure and multi-layer system respectively,and a simplified calculation method for the elastic lateral stiffness and ultimate bearing capacity was proposed.The main work of this paper is as follows:(1)A prototype structure that is steel frame with fuse substructure system was designed,which mainly includes the design method of energy dissipation beam and the selection and verification of member cross-sections,and the reaction spectrum analysis was performed to study the deformation of the structure under the earthquake effect.(2)The single-layer fuse substructure was used as the research object for finite element modeling and analysis.The results show that the plastic deformation of the fuse substructure mainly occurs at the weakened flange of the energy dissipation beam,while the other regions remain elastic to avoid premature buckling of the non-energy-consuming members and improve the seismic performance of the structure;the stress change of each energy dissipation beam section of the single story substructure is approximately the same.(3)9 models in 4 series were established using ABAQUS to study the effects of beam length,weakening distance,weakening length and weakening depth on the seismic performance.The results show that the influence of each factor on the energy dissipation capacity,elastic lateral stiffness and ultimate bearing capacity of the fuse substructure is in the following order:beam length,weakening depth,weakening distance and weakening length;the influence on the ductility of the fuse substructure is in the following order:weakening distance,weakening length,beam section length and weakening depth.Based on that,design suggestions are as follow:the length of beam should be chosen as small as possible within the range of the standard;the weakening distance of beam should be chosen as intermediate as possible within the standard,which is 0.65bf;the weakening length of beam should be chosen as small as possible within the standard,which is 0.65hb;the weakening depth of beam should be chosen as intermediate as possible within the standard,which is 0.2bf.(4)The desirable damage model of the steel frame with fuse substructure was studied and established.8 models in 4 series were established using SAP2000 to study the effects of floor height,fuse substructure span,energy dissipation beam steel grade and fuse substructure location on the seismic performance of the structure and energy dissipation of each member.Based on that,design recommendations are as follow:the floor height of the system should not be designed too high,3600mm is appropriate;the span of the fuse substructure should not be too high,and the ratio of its span to that of the frame beam is suggested to be 0.22-0.29;the steel grade of the energy dissipation beam section of the system should be smaller than that of the frame beam column;the fuse substructure should be set at the side span.(5)The deformation characteristics of the single-layer fuse substructure under horizontal earthquake are analyzed,and a typical yielding mechanism in the critical state was established.The simplified calculation method of elastic lateral stiffness and ultimate bearing capacity based on the assumption of small deformation and the principle of virtual work was proposed,and the method was applied to the multi-layer system.The simulation analysis results were compared with this method for verification.The results show that the maximum difference of stiffness between the calculated value and finite element value is 10%,and the maximum difference of ultimate bearing capacity is 9%,and the maximum difference of stiffness and ultimate bearing capacity of multi-story structure is 7%,which indicates that the method is feasible to calculate the elastic lateral stiffness and ultimate bearing capacity of the structure.