Experimental Study On Failure Mechanism Of Special Staggered Truss Structure System Under Cyclic Load

Staggered truss structure system is a new type of structure,with a better economy,while providing two column of large bays.Recently,domestic and foreign scholars have carried out a lot of research work on staggered truss structure system.Previous studies show that the composite staggered truss structure system collapsed mainly for the diagonal web members’ destruction when subjected to cyclic load.Its energy dissipation capacity and ductility are poor,showing brittle fracture characteristics.In order to improve its seismic performance,the concept of special staggered truss structure system was proposed here,which was to design the middle vierendeel chords of the structure as one type of energy dissipation components.When the structure was withstood severe earthquake action,the middle vierendeel chords took part in the inelastic energy dissipation with the rest members remaining elastic except column base.In this paper,the special composite staggered truss structure system design method was proposed referred to the practice of eccentrically braced steel frame.Based on experiments of the one-third scale models of six composite staggered truss structure systems under cyclic loading,hysteretic and skeleton curves were obtained.Furthermore,structural ductility and deformation capacity,strength and stiffness degradation,energy dissipation capacity and failure mechanism were analyzed.Results of the experiment revealed that special staggered truss framing systems had larger initial rigidity,higher bearing capacity and better energy dissipation capacity.By stiffening the web members and "weakening" the chords of the truss,the failure mechanism of the composite staggered truss structure system was changed.The special composite staggered truss structure systems collapsed mainly for the diagonal chords’ destruction,while the ordinary ones mainly for the diagonal web members’ destruction.