Research On Anti-Collapse Performance Of Three-Direction Connected Semi-Rigid Beam-Column Joint Substructure

With the continuous improvement of engineering technology,the building structure is developing towards large-scale and complex direction.Once some key components in structure fail,the remaining structure may not be able to bear the unbalanced load caused by local damage of structure,resulting in progressively collapse of structure,which will cause huge casualties and economic losses.Semi-rigid joints have good energy dissipation capacity and hysteretic performance.However,most of the existing semi-rigid joints are bolt-weld connections such as extended end-plate connection,T-stub steel connection ect.There are still a lot of welding in these connections,which leads problem of stress concentration caused by welding effectively to not being avoid.Some semi-rigid joints are also connected by fully bolts such as angle connection ect.,but the number of connectors is large and structure of connector is complex.In this paper,based on the existing connection forms of semi-rigid joints,a new type of fully bolt connection,namely three-directionally connection is proposed,which is simple in structural form,convenient in installation,high in bearing capacity and good in rotation capacity.Combining theoretical analysis and numerical simulation,the anti-collapse capacity of the three-direction connected semi-rigid beam-column joint substructure is analyzed.The main research contents and conclusions of this paper are as follows:(1)A connection form of three-direction connection semi-rigid beam-column joint is proposed,and the mechanical model of three-column and double-beam beam-column joint substructure is established,and under the condition that the central column fails,its stress analysis is carried out.On this basis,its load-displacement curve formula is derived.(2)According to the existing experimental research data of the collapse performance of the top and bottom angle steel and double-web angle steel beam-column joint substructure,the metal fracture damage model is established by ABAQUS and its numerical analysis is carried out,which indicates the model is accurate.On this basis,the connectors proposed in this paper are used to replace the top-bottom angle steel and double-web angle steel,and the numerical calculation is carried out.It is indicated that the anti-collapse capacity of the three-direction connection semi-rigid beam-column joint substructure can reach the collapse resistance level of the top-bottom angle steel and double-web angle steel beam-column joint substructure in the calculation results.(3)The influences of the thickness of the connector,bolt diameter,bolt spacing on the anti-collapse capacity of the substructure are analyzed.The results indicate that the initial stiffness,yield load,peak load and ultimate load of the substructure can be improved with the increase of the thickness of the connector.Increasing bolt diameter,the initial stiffness,peak load and ultimate load of the substructure can be improved,but the effect on the initial stiffness of the structure is small.Bolt spacing has little effect on the collapse resistance of the substructure.In the small deformation stage,increasing the thickness of the connector and the diameter of the bolt will reduce the arching effect of the structure.Based on the research on the anti-collapse of steel frame structure,the influence of floor slab on the anti-collapse capacity of substructure is analyzed.The results show that the yield load,peak load and ultimate load of the three-direction connected semi-rigid beam-column joint substructure with floor slab are 173%,54% and33% higher than that of the steel frame structure,respectively.It can be seen that the impact of floor slab on the anti-collapse capacity of the substructure is significant,and it is necessary for the impact of floor slab on the anti-collapse capacity of the structure to be considered.(4)Based on the alternate load path method,under the conditions of central column failure and side column failure,the collapse resistance of a four-span and six-story planar frame structure is analyzed.The results show that the anti-collapse capacity of the structure is the lowest when the side column fails.