Seismic Behavior Research Of Steel Frame With Irregular Connection Using Unequal Depth Beams And External Diaphragm

Steel special moment frames(SMFs)are extensively used because theses excellent energy dissipation,ductility and convenient construction.As a critical part of the steel frame structure,the beam to column connection plays a major role in the seismic performance of the frame.The ductility of the joint directly determines the transmission path and failure mechanism of the whole structure.With the continuous development of the building function,the structure form tends to be complex,and the Irregular connection with unequal depth beams begin to appear in a large number of industrial and civil buildings.With the continuous enrichment of frame structure forms,the construction of connection locations tends to be complex.In actual project,the height of beam section is often different for the interior column connections.In this case,the force mechanism of the connections is obviously different from that of conventional structures.However,there is absent theoretical support for the construction of such related connections in existing specifications,so it is necessary to make further research on the seismic performance of such irregular connections.However,in practice projects,due to the lack of theoretical support and experience,such irregular connections can only be designed according to the conventional connection specifications,resulting in the limited application of related structures.Therefore,it is necessary to analyze the seismic performance of the irregular connections of this steel structure and discuss the mechanical mechanism and seismic performance.Although some studies have been carried out on the irregular connections with unequal beam height at home and abroad,the research scope is mostly limited to the elastic-plastic development mechanism of the components themselves,and it is impossible to comprehensively determine the effect of local connection characteristics on the seismic performance of the whole structure.According to the above situation,the seismic performance of steel frame structure with unequal beam height is studied based on the structural scale.The research is mainly as follows:(1)In order to reasonably allocate computing resources,multi-scale model is used for numerical simulation.By using the method of scale separation,the force characteristics of the detail connections and the macroscopic response of the whole structure are calculated in a coordinated way through a reasonable connection mode,and the computational efficiency of the numerical model is effectively improved while retaining the geometric features of components.And the reliability of multi-scale model is verified by a series of examples.(2)According to the related specifications,three-,nine-and twelve-layer frames are designed,and the elastic-plastic properties of the independent beam-column joints are analyzed.(3)Based on pushover analysis method,the seismic performance of steel frame in the case of rare earthquake is studied,and the capability curve of the structure and the deformation characteristics of the target displacement are obtained.The plastic trend of connections under lateral load and the stress state of connections in critical path are evaluated.(4)The dynamic elastic-plastic time history analysis of steel frames is carried out to obtain the dynamic response under the selected earthquake ground motion time history,and the seismic performance of steel frames under various connection structures is evaluated according to the stress state of local connections and the deformation characteristics of connection domain.