Numerical study of steel plate girders under shear loading at elevated temperatures

Abstract

The ultimate shear capacity of steel plate girders may be influenced by shear buckling, an important and common instability phenomenon occurring in plate girders with slender webs. The transverse loads and consequent shear effort applied on such beams have a large impact on the webs, leading to the possible collapse by shear buckling. In a fire situation, the buckling phenomena in these structural elements are amplified due to the reduction of the steel mechanical properties caused by the elevated temperatures. Recently, there has been an increase in the use of those plate girders, arising from the search for more economical and competitive solutions. However, no specific rules for shear buckling verification in case of fire are given in Eurocode 3 (EC3).After the validation of the numerical models against experimental tests from the literature, an extended number of geometrically and materially nonlinear numerical analyses including imperfections (GMNIA) have been performed dealing with the evaluation of the effect of rigid and non-rigid end posts on the ultimate shear capacity of steel plate girders under fire. The obtained numerical results are compared with the specifications of EC3 for the design at normal temperature adapted to elevated temperatures. These specifications are non-conservative and, for this reason, a new design proposal harmonized with the EC3 principles is presented in order to evaluate the ultimate shear capacity of steel plate girders in fire situation.