Research On Mechanical Behavior And Design Method Of Cold-formed Steel Trusses

This paper establishes A, B, C, D four groups,20 different size, different abdomen stem form cold-formed steel truss finite element model, and analyze their vertical ultimate bearing capacity under nonlinear finite element analysis. Through analysis results can reach the following conclusion:Truss destruction features is that ends compressed inclined abdomen stem happen buckling, generating large deformation, and penetrates the chord webs; the stress of nodes are bigger; chords do not reach the yield strength when destroyed, the stress of the chords' middle section is large. Along with the increase of span, the chords' stress gradually increases, closing to its yield strength.Based on above, change variable parameter to analyze vertical ultimate bearing capacity of cold-formed steel truss. Draw main influence factors of vertical bearing capacity of trusses are chord size, thickness of abdomen stem and chords, abdomen stem's cross-section, steel level.In other conditions remaining unchanged, reducing chord size, carrying capacity is reduced, and carrying capacity reduction decrease as span increasing. In other conditions remaining unchanged, as the rods thickness decreases, limit load and deflection of midspan under limit load gradually reduce. In other conditions remaining unchanged, when abdomen stem section changes to U steel, same size with the C steel, limit load and the deflection of midspan under limit load reduce. When chord section changes to U steel, same size with the C steel, limit load and deflection of midspan under limit load reduce, but have little difference. When steel yield strength fy=334.03MPa changing to fy=235MPa, limit load and deflection of midspan under limit load gradually reduce.Secondly, analyze linear and nonlinear buckling of the trusses, first-order buckling of A, C group is ends compressed inclined abdomen stem buckling, first-order buckling of B and D group is bent stem happen buckling. Introducing defects updating model, consider defects, material nonlinearity and the geometrical nonlinearity, truss load-bearing capacity reduce greatly.Finally, discussing the steel truss design methods, verify that using "Technical code of cold-formed thin-wall steel structures" to design trusses is safe, and steel quantity of thin-walled steel truss is litter than steel quantity of hot-rolled steel truss.