The Effect of Creep on Steel Columns at Elevated Temperatures

In this thesis, the effect of creep on steel columns at high temperatures is investigated with the objective of furthering performance based design codes for structures subjected to fire. First, the phenomenon of creep, which is a rate dependent deformation process that occurs in steel at elevated temperatures, is studied. The specific processes that govern creep, how its deformation is assessed, and recent research in the area are all reviewed. Then how creep can be included in numerical simulation models of steel at high temperatures is considered. With knowledge of the general framework for high temperature creep models, a creep model for ASTM A992 steel is proposed. The model is calibrated to high temperature experimental creep data and then used to assess the differences in steel column behavior when creep is included in the analysis. Steel columns subjected to different temperatures distributions across its cross section, various boundary conditions, and different loads are all analyzed in a parametric study and design implications are discussed. Finally, a computationally efficient geometrically nonlinear beam finite element for performing coupled plastic-creep analysis is presented.