Behavior Of Beam-Column Connections With Opening On Beam Webs In Steel Frames Under The Sudden Loss Of A Central Column

After the sudden loss of a central column in steel frames,the beam-column connections above the failure-column undertake its load and transfer that to other components connected to the joints,both bearing capacity and deformation capacity of the beam-column connections determine the ability of the structure to resist the progressive collapse.Studies on the behavior of the welded joints in steel frame under the sudden loss of a central column show that the joints have lower bearing capacity for the premature cracking.The connections with opening on beam webs allow the construction equipment pipeline through the beam to save space of the building,the reasonable opening can can make the plastic hinge outward,protect the welding area and improve the deformation capacity of the joints.After the sudden failure of a central column,the performance of such joints has not been studied,this paper will study the behavior of beam-column connections with opening on beam webs in steel frames under the loss of a central column.Firstly,refined finite element models with the consideration of the material damage are established and the accuracy of the models is checked by simulating experiments.Secondly,the joints are divided into three groups in accordance to the span-to-depth ratio,the behaviors of the basic joint and a typical joint with opening whose span-to-depth ratios are 9 are made analysis and comparison to analyze the influences on the behaviors caused by the opening on beam webs,such as failure mode,bearing capacity,deformation capacity and etc.Finally,the joints with different parameters are simulated to study the influences on the deformation capacity,mechanical behaviors and the development of resistance mechanism caused by the hole parameters(the positionand diameter of the hole)and the span-to-depth ratio.The studies shows that opening on beam webs can improve the bearing capacity and deformation capacity of the joints,delay the failure and make the resistance of the bending mechanism reduced,while the resistance of the catenary mechanism is greatly improved,more resistance will be provided by the catenary mechanism instead of the bending mechanism.Hole parameters and span-to-depth ratio influence the deformation capacity,the development of the resistance mechanism and the final resistance greatly.Based on analysis,the reasonable value range of the hole parameters with different span-to-depth ratio will be suggested to provide reference for the follow-up studies and application.