Seismic Performance Evaluation Of Steel Frame Structures Of Existing And Modidied Joints Form

Seismic evaluation of structural performance considering only the structural deformation, without considering the cumulative damage of structure, frame beams were the the main energy consumption members of the structure for the design of “strong column and weak beam” under large earthquake.However, the energy dissipation capacity of frame beams may not as expected,the domestic and foreign past earthquake disaster data display that steel structure node region may be brittle fracture under the action of earthquake, which led to the failure of the structure, so, good energy dissipation capacity of steel structure have not been brought into full play. Steel was prone to corrosion in corrosion environment.but, at home and abroad on the assessment of steel member or structure, the influence on the mechanical properties of steel corrosion was not considered.Attenuation of seismic performance for the existing steel structure members and structure in service due to steel corrosion was researched, and the double parameter seismic damage model considering the deformation and energy dissipation was put forward,then the seismic vulnerability of different age of steel frame structure was assessed based on the different damage index, and the measures of improvement of key energy consuming parts on the structure was put forward.In this paper, the main research work carried out the following aspects:(1)Through salt spray indoor accelerated corrosion and pseudo static destruction test of simulated coastal atmospheric environment effect on Q235 B beam column welding frame node connection without coating, and the test, plastic deformation and failure characteristics of steel frame joints were developed with different corrosion rate and different loading system,the bearing capacity and deformation capacity and energy dissipation capacity of the decay relationship index with the corrosion rate, to fill the domestic blank in research on seismic performance of corroded steel structure member.(2)The damage model proposed is applicable to steel structure frame joints, and considering the effect of corrosion on the seismic behavior of the joints,the time-varying damage model is proposed for the steel frame structure joints in different corrosion degree by considering the two parameter of deformation and energy dissipation.(3)In order to considering the effect of bearing capacity,deformation and energy dissipation of component and the structure due to steel corrosion, different damage indexes of structural were used to evaluate the seismic performance,then the multi-age vulnerability model of steel framework was established and the vulnerability surface was given considering the time parameter.(4)The equally intensity steel joint which made the plastic hinge outward from joint zone without decreasing its stiffness was proposed to improve the seismic performance of structures by increasing the deformation and energy dissipation ability of the joint.