Research On Performance Of Cold-formed Thin-walled Steel Structure With Semi-rigid Connection

The joint attended mode of the cold-formed thin-wall steel structures always use screw bolt or self-tapping screw to connected. These fashions can both assurance the credibility of the connection , be ease to execution and pick up the speed of the construction progress. But in the practicable engineering design, these attended modes always be simplified to the perfect articulated mode to design (especially in the girder grillage system construction ). These assumptions can simplify the design and analysis greatly, but in fact these connections have the capability, which is called semi-rigidity, to afford certain moment of flexion and deformation. Because the cold-formed thin-wall steel structures have the characteristics of semi-rigid connection , in analysis it is necessary to take the influence of the inner force and deformation in structure because of the semi-rigidity.This article aim at characteristic of the member bar and tectonic characteristics of node in the cold-formed thin-walled steel structure, on the base of some basic assumptions, starting from commonly classic rigidity equation of the beam-column unit and using change part item in element stiffness matrix to get a matrix equation which considered in effects with thin-walled bar, structural geometric nonlinear and flexibility of the connection ,also get a unit rigidity equation with end fixing random semi-rigid connection. Using the modified element stiffness matrix which mentioned above, work out the finite element programming which use to reach semi-rigid connection in cold-formed thin-wall steel structure. Also use this program to proceed nonlinear analysis with semi-rigid connection in cold-formed thin-wall steel structure.Through the analysis of the inner force and displacement in the cold-formed thin-wall steel truss with semi-rigid connection ,we find that : comparing with the modal builded with ideal pin joint ,both the node vertical displacements and bar axial forces in the semi-rigid modal are relatively smaller, so we can conclude that: the increase of the rigidity in the joint will lead to the increase of the entire rigidity the truss, and because of the weak flexural rigidity in the bars and small moments in the semi-rigid joints ,the effect of the secondary stress is small enough to be neglected. Through the calculation of the bearing capacity of the cold-formed thin-wall steel truss with semi-rigid connection, we find that the calculated bearing capacity is higher than that in the modal builded with ideal pin joint ,and the effective length is the influencingfactor.And after the analysis of the cold-formed thin-wall steel frame with semi-rigid connection simplified from keel system, we find that: the lateral rigidity in the frame is so weak that it can't offer the required lateral rigidity to the whole structure, it shows that the plate connected to the column is the main component to resist the lateral force.In the analysis of modified semi-rigid connection of cold-formed thin-wall steel structures frame , it is found that the lateral rigidity is far more better than the former.This kind of frame may be one of trend in development of cold-formed thin-wall steel keel system.