Design And Seismic Performance Analysis Of Reduced Beam Section Connections In Steel Frame

Reduced beam section(RBS)connection is a form of node that can effectively prevent brittle fracture at the beam-to-column connections.At present,RBS connection design mainly refers to FEMA-350,but the calculation process of the method is complicated and doesn’t consider the infill wall’s role in the steel frame.American scholar Nestor Iwankiw improved the design method in the specification,but did not consider the effects of dead load and live load and the arrangement of the infill wall.This paper’s research contents base on the improved design method of Nestor lwankiw,combining with the actual situation of steel frame’s arrangement,and considering the influence of dead load,live load and infill wall in steel frame.According to restoring force model for oblique bracing of filled wall and corner crushing stress limit,the variation law of the beam bending moment can be theoretically derived during the crushing of the corner of the filled wall,applied to the design process of the reduced beam section in order to comply with the modified design method which is more actual and revised.Without absence of the infill wall,a steel frame integrated office building in Heze is designed according to the modified design method,and the calculated depth of the flange weakening is in accordance with the FEMA-350.Five sets of depths were selected similar to the calculated depth to establish the overall steel frame model by SAP2000 software.Through the Push-over analysis,each the steel frames model’s seismic bearing capacity and development can be obtained.The results show that with the same apex displacement,the increase of the weakening depth of the beam flange makes the steel frame play the plastic hinge rotation ability of the steel beam on the higher floor and increase the ductility.Compared with other steel frame models’ bearing capacity and the development situation of the plastic hinge,the calculated depth of reduced beam flange can more effectively exert the plastic hinges’ rotational capacity of the steel beam on the basis of ensuring the bearing capacity.With arrangement of the infill wall,a steel frame substructure with single layer and span is designed according to the modified design method,and the calculated depth is within the scope of FEMA-350.Five groups of reduced beam flange depth close to the calculated depth is selected to establish finite element model by ABAQUS software.Under the action of horizontal monotonic loading,the load-displacement curves of the steel frame and the stress distribution diagram of the joint region can be obtained after the appearance of plastic hinge.By analyzing the load-displacement curves and the stress distribution diagram,it is found that with the increase of the reduced beam flange depth,the high stress region gradually shifts to the flange reduced section,but the bearing capacity of the steel frame is continuously reduced.Comparing the steel frame models of each group,when the flange reduced depth is close to the calculated depth,the high stress region can be transferred to the flange reduced section under the premise of ensuring the bearing capacity of the steel frame.In this paper,for the two cases of absence of infill wall and arrangement of infill wall,finite element model is carried out by SAP2000 and ABAQUS software respectively,and the seismic bearing capacity and plastic hinge development can be obtained and can be analyse a reasonable flange reduced depth.It is consistent with the calculation result of the modified design method and meets the requirements of FEMA-350.It verifies the rationality of the modified design method and provides a reference for reduced beam section’s design of similar engineering.