Static And Dynamic Analysis Of Staggered Truss Framing System In Steel Structure

Based on the review of the theoretical study and practical application of staggered truss framing system, this dissertation mainly achieves the following aspects aiming at improving the defects in the study:With regard to the theory of static elastic analysis, the paper, applying the analysis of the bearing characteristic, puts forward a mechanical model and a calculating method of internal forces of staggered truss structure subjected to vertical loads. As for Vierendeel staggered truss structure, the staggered truss structure can be simplified as a rigid frame with no lateral deflection with the introduction of rotational stiffness and transfer coefficient. Examples and calculating results show that the number of members involved in interaction is decreased greatly and iterative convergent rated is improved to a large extent so as to lessen the amount of computation. Concerning the staggered truss frame with diagonal braces truss, calculating formula and methods of member internal forces are presented. According to the analysis of the bearing characteristics and the way of force transference in staggered truss structure under lateral loads, assuming that the stiffness of floor was infinite and torsional effect could be ignored, a plane cooperative mechanical model for calculating internal force in member is brought about and calculating formula and methods of relative lateral displacement between neighboring storeys and total lateral displacement stiffness between storeys are provided as well. Examples and calculating results reveal that the method adopted in the paper is simple and of great precision. Two methods of dealing with second-order effect are listed as follows: first, the influence of second-order effect can be regarded as equivalence to deduction of lateral displacement stiffness between storeys. In this way, calculating formula for lateral displacement stiffness between storeys considering second-order effect and a plane cooperative mechanical model for calculating internal force in member after taking second-order effect and space integral effect into account. Second, a structure is equal to a built-up compression member. By computing the differential equation for this member, deformation curve of the given structure under lateral load and vertical load can be obtained. Based on theassumption that the structure is viewed as a built-up compression member, the paper comes up with calculating method adopting energy method to work out critical load of overall stability. In addition, the paper offered calculating method of cross section characteristics of chord member in view of the influence on floor slabs, along with modified formula including torsional effects for the shear distribution in members.With relation to finite element analysis of seismic response, by virtue of the characteristics that principal members of staggered truss steel structure are thin-walled bar, the paper analyzes coupling relation among various deformation in thin-walled bars and deduces geometric stiffness matrix of elements considering factors, such as the influence of shear force, second-order effect, warp distribution and section opening and close. On the presupposition of ideal elastoplasticity, elastoplasticity stiffness matrix of elements is displayed. Dynamic equilibrium equation is established, based on space bar-floor model assumption. Then, a study is conducted through analysis examples of seismic response subjected to Vierendeel panel length, damping ratio and input dimension of seismic wave, analysis results show that the length of Vierendeel panel and damping ratio exert greater influence on structural dynamic response, while the input dimension of seismic wave has fewer impact on structural displacementIn the matter of simplified analysis about earthquake action, grounded on mode superposition method, the paper provides concrete calculating formula and method of seismic response affected by the input of multi-dimensional seismic wave and discusses the reasonable number of vibration mode. By means of constructing a structure with an easily-gained natural vibration frequency and vibration modes, the paper introduces simplified calculating approach to natural vibration frequency and vibration modes of staggered truss structure while referring to the matrix perturbation theory. With this approach, the structural interlayer shears achieved by equivalent base shear method and mode superposition method are compared and contrasted. The results make it clear that the percentage discrepancy will widen along with the numbers of stories, attributed to different computation results obtained by the equivalent base shear method and mode superposition method respectively.