Seismic Performance Analysis Of Semi-rigid Connection Single Oblique Rod Eccentrically Braced Steel Frame

Beam-column joints was the main connection of the frame structure,the performance of joints had influence on the structural internal force distribution,the stiffness and the seismic performance of the structure.In traditional structural design,the connection of beam-column joints was designed as rigid connection or hinged connection,but due to the influence of material nonlinearity and geometric nonlinearity,the design results was different from the actual stress state.And multiple seismic damage showed that the beam-column joints often occurred the brittle failure.In order to avoid the brittle failure of the beam and column joints,we can adopt the semi-rigid connection.The semi-rigid joints had a quick construction speed,it could bear partial bending moment and shear force.Meanwhile,the semi-rigid joints had good energy-dissipating capacity.Moreover,the semi-rigid joints would cause the redistribution of structural internal force,as a result,the force of the structure which was under the vertical load is more reasonable.Consider the economy,with the semi-rigid joints was used,the size of components and the amount of steel can be reduced,so that the building costs would decrease.Though the semi-rigid joint steel frame had such good advantages,the disadvantages of it can not be ignored.The main disadvantage was that the lateral stiffness of this structure was low,it belonged to the single lateral force system.When the horizontal load was big,the lateral displacement of the structure was large,it was difficult to meet the limitation of the standard.In order to make up for the deficiency of the lateral stiffness of the semi-rigid frame structure,the support system was added in the semi-rigid frame structure.The braced semi-rigid connection steel frames was belong to the double resistance to lateral force system,the brace could increase the lateral stiffness and enhance the overall stability of the frame.The bracing system include the centre brace and eccentrically brace.Under the rare earthquakes effects,the centre brace was easy to happen compressive buckling,which would cause that the lateral stiffness of the structure decreased sharply and the reliability of the structure reduced.For the eccentrically braced frame structure,under the frequent earthquakes and moderate earthquakes effects,the EBF structure was in elastic state,Its performance is similar to the central support frame.On the other side,under the rare earthquakes effects,only the link beam yielded while other Component was still in elastic state,and the earthquake energy was absorbed by the plastic deformation of link beam.Eccentrically braced system could effectively protect the brace and had good energy dissipation,it also could effectively save the steel.On the base of disadvantages of semi-rigid joints frame and sufficient strength,the lateral stiffness,stability and energy dissipation capability of eccentrically braced frame,A new seismic structure which combined the semi-rigid joints with eccentrically brace was formed.Eccentrically brace system increased the lateral stiffness and height of the semi-rigid frame structure,the semi-rigid joints further enhanced the hysteretic behaviour and energy dissipation capacity of structure.Therefore,this paper analyzed the seismic performance of this new seismic structure system in detail,which included the hysteretic behaviour,the energy dissipation capacity,the ultimate bearing capacity,the ductility and the plastic deformation capacity.Firstly,the research status of eccentrically braced semi-rigid connection steel frames was introduced,the classification and M-? curve of semi-rigid joints were described in details,besides,the characteristic and design theory of the braced frame structure were stated.Secondly,the establishment and verification of finite element model of eccentrically braced semi-rigid connection steel frames was described.The finite element models of single sway sod eccentrically braced semi-rigid connection steel frames with different floors,spans and rotation stiffness of beam-column connections were established by ANSYS17.0,and relation between the natural vibration frequency of structures and the connection stiffness,floors and spans were obtained by modal analysis.the curve of structural natural period of vibration was plotted,and the influence of brace,rotation stiffness of beam-column connections,floors and spans were analyzed in detail.Thirdly,On the base of modal analysis,the time-history analysis of single sway sod eccentrically braced semi-rigid connection steel frames was completed.The top displacement,layer displacement and base shear under the actual seismic effects were studied,and the influence of brace,rotation stiffness of beam-column connections and the peak acceleration of seismic wave were analyzed in detail.The reaction of structure under seismic load was obtained.Finally,the finite element models of eccentrically braced semi-rigid connection steel frames were established.The hysteresis performance of the structure under cyclic load were studied.the hysteresis curve,skeleton curve,ductility coefficient,energy dissipation coefficient and failure mechanism were obtained.The influence of brace,rotation stiffness of beam-column connections were analyzed in detail.