Study On Seismic Behavior Of Steel Double-channel Built-up Box-shaped Chords Of Special Staggered Truss Steel Frame Structure

The composite staggered truss steel frame structure has large bearing capacity and lateral stiffness,but its ductility is poor.In order to improve the seismic performance of the structure,the special staggered truss frame structure is proposed by considering the mechanical characteristics of composite staggered truss frame structures.In special staggered truss frame structures,the steel trusses are designed in such a way that the inelastic activity is confined to a special segment(i.e.,the Vierendeel panel)near the midspan during a seismic event.The rest members of the structure remain elastic.The failure mechanism of the structure indicates that the reasonable design of the special segment is the keypoint of the seismic design of special staggered truss frame structures.The advantages of the steel built-up member are more distinguished than that of other types of cross-sectional forms.Compared with its counterparts,the materials of steel built-up member are used more reasonably,its rigidity is greater,and its anti-torsion performances are better,and are often used in earthquake-resistant structures as bracing members in braced frames.However,little is known about the behavior of steel double channels under reversed cyclic bending.The special segment of the special staggered truss belongs to members subjected to combined axial load and bending under rare earquake.to examine the seismic behavior of a special segment for applications when the chords of a special staggered truss steel frame structure use double-channel built-up box-section members,a quasi-static test were conducted on a full-scale double-channel built-up box-section member without regard for axial force.Experimental results indicate that the double-channel built-upbox-shaped member under reversed cyclic bending exhibit a plump shuttle-shaped hysteretic curve,and the plastic hinge was formed at the bottom of the specimen,where local buckling of web and flange occurred.The brittle fracture occurred in the region that connects the gusset and channels at the late loading stage,leading the fracture of the channel flange until the failure of the specimen.Based on the experiment,numerical simulation was used to study the seismic behavior of the seismic behavior of a special segment for applications when the chords of a special staggered truss steel frame structure use double-channel built-up box-section members,The main parameters were coefficient of axial force,stitch spacing,height of gusset plate,the stiffener spacing at the plastic hinge,the lateral bracing settings located at the plastic hinge,the channel web thickness ratio.Finite element finite results indicate that,axil compression has more adverse effects on the hysteretic behavior of double-channel built-up box-shaped memberscompared with axial tension.The reduction of stitch spacing can improve the degradation of bearing capacity.The larger height of gusset plate could increase the initial stiffness,bearing capacity and energy-dissipation capacity.The stiffeners at the plastic hinge region can strict the local buckling deformation of the plates,leading to the increasing of bearing capacity,and the decreasing of degradation of bearing capacity.The reduction of the channel web thickness ratio can improve the degradation of bearing capacity and energy-dissipation capacity.