Study On The Performance Of Spacial Steel-frame Constructions Under Cyclical-loading

At present, most of the research about the seismic-resistant performance of steel frame focus on the performance of the plane steel frames and joints, and the research rarely relate to the performance of the spacial Steel-Frame. Actually, the frame is spacial construction. Therefore, embarking from the frame's whole seismic-resistant performance and considering three-dimensional effect, this paper thoroughly studies the seismic-resistant performance of the rigid spacial steel-frame constructions under cyclical-loading; by even better coordinates the relationship between the structure's strength, rigidity and ductility has the extremely important practical significance regarding the instruction design work.This paper applies material nonlinear and geometry nonlinear FEM Model (finite element method) to exactly simulate and thoroughly analyze the overall behaviors of the rigid spacial steel-frame constructions under cyclical-loading. The load-bearing condition of the rigid spacial steel frames construction in a variety of situations was really simulated through the calculation and analysis of 21 species of 5 series. The major parameters including constant axial compression ratios, ratio of high to span, length of beam, slenderness ratios of columns and different frame joint are studied. The main conclusions are: The first plasticity-joint of the breakdown rigid spacial steel-frame constructions is in the end of the first-floor-frame beam, and the last one is in the heel of column. In the design of engineering, the welded join security of the intermediate frame-beam end must be sufficed, and suffice that the base well restraints the heel by construction, prevent the premature breakdown of side column and intermediate column by enhancing the safe coefficient of side column and intermediate column. The stress is complicated in the welded joint of edge and web, besides the stress concentration and the three-dimensional stress states is obvious; this pricks up the possibility of the brittle fracture of welded joint. In the design of engineering, the view that considers that all bend force is bore by the edge and all shear force is bore by the web maybe make the design of welded joint be insecurity and pricks up the possibility of the brittle fracture of welded joint. The frame with the dog-bone joint, cover-plates joint and welded-haunch joint can make the plasticity-joint depart from the end of beam, and reduce the welded joint stress, and avoid the brittle fracture of welded joint.In conclusion, the FEM Model can well simulate the behavior of the rigid spacial steel-frame constructions under cyclical-loading. The load-bearing performance of the rigid spacial steel-frame constructions is analyzed exactly in this paper. The work and the result are very useful for revising design specifications and guiding design of engineering. This paper will play a basic role in the further study on spacial steel-frame constructions and analyzing the seismic-resistant behavior of whole structure.