STRUCTURAL STABILITY OF LACED BUILT-UP COLD-FORMED STEEL COLUMNS
Cristiane Cruxen Daemon d´Oliveira e Bastos1; Eduardo de Miranda Batista1
1 COPPE-UFRJ
doi:10.20906/CPS/CILAMCE2017-0223
Resumo
Laced built-up columns composed of cold-formed steel members have several applications, such as in industrial buildings, offering advantages of lightness and fast and easy transportation, erection and installation. Two main effects distinguish the behavior of these columns from other structural systems: (i) the effect of shear deformations and the interaction between local and global buckling modes. The main design standards and specifications do not provide sufficient guidance for the design of this type of cold-formed structural system. From the literature, we verify that very few tests have been conducted on this type of built-up columns. There are analytical methods to obtain critical and collapse loads of laced built-up columns, but it is necessary to evaluate the precision of these methods when applied to thin-walled members. For this, experimental and numerical analyses are needed, especially in the present case of spatial built-up laced columns composed of cold-formed steel sections. The objective of this paper is to present the results of real scale experimental tests carried out in spatial laced built-up columns, designed with stiffened channel cold- formed steel members. The 6 tested spatial laced columns have respectively 6, 12 and 16m length and 0.8 and 1.25mm plate thickness, all with 400x400mm cross section. The laced column longitudinal members, composed of two stiffened channel members connected with self-drilling screws, were previously analyzed by the finite strip method, in order to identify its buckling loads and modes. For the built-up column as a whole, elastic buckling and nonlinear analyzes were performed. Four analytical methods were applied to obtain global buckling including shear effect: Engesser, Timoshenko, Bleich and Eurocode 3. The results indicate quite similar critical elastic buckling loads, and good agreement with those from the FEM buckling analyses. Experimental results of the critical loads, obtained by Southwell plot method, performed significantly lower than numerical and
Palavras-chave: laced built-up columns; cold-formed steel structures; buckling; elastic critical load; column strength