Study On Seismic Behavior Of Staggered Truss Steel System

As a new type system of steel structure, the staggered truss system has been analyzed theoretically and applied into some projects internationally. On this basis, the structure features, simplified calculation method, force characteristics under different loads and design theory of members are studied. Then, the effects of different factor settings on staggered truss systems are researched deeply by static nonlinear analysis Push-over. The main conclusions are outlined as the following:Frist, the contents including layout principles for earthquake resistance, theoretical calculation for loads, simplified method of lateral stiffness, internal forces calculation method under vertical loads and horizontal earthquake are systematically summarized.Second, under vertical loads and horizontal earthquake, the Load-bearing Capacities of Staggered Truss Structure are researched by analysis software Etabs. The distributions of internal forces are abtained within the extent of elasticity. In addition, the vibration modes and deformation under horizontal seismic actions are analized. The design method for the members of staggered truss is illustrated including both intensity and stability.Third, from the push-over analysis, all the examples of this paper can satisfy seismic fortification requirement under rare earthquake of intensity 8. Also, the curves of Capacity Spectrum, development of plastic hinges, destruction pattern of the hybrid staggered truss are determined. All in all, the plastic hinges develop gradually from lower to upper, Vierendeel panel to both sides. Finally, most of the plastic hinges are appeared on the tilted belly poles of the lower trusses, but not on the side columns. Because of this, the first or second floor becomes the weakest parts of the hybrid staggered truss.Forth, through push-over analysis of hybrid staggered truss with different parameters, the conclusions are as following: under rare earthquake of intensity 8, besides the first story, when the ratio of height to width increases, the inter-story drifts increase; As the ratio of length-width increases, both the lower inter-story drift and the upper story displacement obviously enlarge; Moreover, the inter-story drift of weakness floors can be effectively reduced by using wind bracing instead of diagonal brace or adding lateral brace or setting longitudinal brace. Also, the concrete filled steel tube and setting truss on the first floor are suggested in the regions seismic fortification.Design theories and methods of the staggered truss system are illustrated in the paper. Then, it's aseismic behavior is evaluated to help engineers find ways to improve the new structural seismic performance. Meanwhile, some regular conclusions and suggestions are given making the system applicated and generalized conveniently.