Experimental And Theoretical Study On Cold-formed Thin Wall Steel Structural Members Of Low-rise Buildings

Although the research and application of the cold-formed thin-walled steel structures has been extended widely and the remarkable achievements in this field have been gained, some key problems have not been solved. As known, some sectional characteristic parameters needed by the analysis of critical buckling stress are not clearly definited in the specifications, including the Saint-Venant torsion constant of the cross section (J), torsional warping constant of the cross section (Cw), location of shear axis (x0), elastic modulus for effective section calculated by a stress relative to the extreme compression strain (Se), and the correlativity between global buckling, local buckling and distortional buckling. It is very difficult to calculate above parameters definitely in engineering design.At present, the cold-formed thin wall steel structures for residential buildings have various types. In the North America, Japan and Australia, the steel materials, section form of members and structural system are different. Even so, they are of similar composition of the structure, in which the steel keels are arranged basically according to-certain module spacing, different support systems are appranged between the steel keels, the structure-plate, the heat preservation thermal insulation material, as well as the surface layer decoration material are installed in turn on the both sides of keel skeletons. All these components forms an extremely reliable "structural system of the dense ribs".The cold-formed thin wall steel structures applied to residential building systems in Australia are different from that of other systems. They have two remarkable features:high strength of material and ultra thin wall of member section. All members have uniform cross section that is common C-shape section with the sectional sizes of 40mm×90mm and the wall thickness ranged from 0.55mm to 1.15mm. The advantage of using uniform member sections is that the mechanical behaviors of structural members can be summarized through the analysis of an element.The high strength thin wall component brings new problems, such as material properties, buckling distortion and the relevant of all buckling mode and so on.In order to solve urgent need in the project application, this article tries to build design formula and form which can be easily and conveniently used through the experimental study, theoretical and the simulation analysis. In this paper, G550 high-strength steel which Shanghai Baoshan Iron and Steel LanCui Co. produced was used. The stress-strain relationship of grade G550 steel and other properties have been obtained.High-strength cold-formed thin wall steel structure pull rivet failure mode and bearing capacity formula have been obtained through different connected forms, different diameter blind rivets to connect multiple sets of test specimens, by their own force characteristics, failure modes and ultimate strength, and the theoretical analysis and calculation results were compared, the first time in our country are given.Through accurate experiment and exhaustive analysis which carries on to three girder trusses, as well as 29 girder truss finite element analysis, gave allowed load form about different span, different girder truss given for the first time in our country。Through K-brace wall framing test under both vertical load and horizontal load, the wall framing failure mode, mechanical characteristics and bearing capacity have been studied. Wall frame column local buckling occurs first, then column foot appears damaged or destroyed by the pull and pressure. The calculation and analysis of the ultimate bearing capacity of the wall frame is summarized.