Time-Dependent Buckling of Steel Plates Exposed to Fire

This paper reports on a preliminary analytical study examining the time-dependent behavior of steel plates subjected to fire temperatures. Simply-supported rectangular plates under uniaxial compression are considered. Isochronous stress-strain curves are utilized to approximate the time-dependent behavior of steel at elevated temperatures. The creep model by Fields and Fields for ASTM A36 steel is used to construct isochronous stress-strain curves. Using the concept of time-dependent tangent modulus, closed-form formulas are developed to model the creep buckling of steel plates at elevated temperatures. These nonlinear equations are evaluated to visualize the time- and temperature-dependent behavior of steel plates in the form of Creep Buckling Curves and Isochronous Buckling Curves. The creep buckling expressions are further utilized to study the effect of width-to-thickness ratio (slenderness ratio) on the creep buckling phenomenon of steel plates at elevated temperatures. Results from creep buckling analyses presented in this paper indicate that the buckling strength of plates made of ASTM A36 steel can be highly time-dependent for temperatures at or above 500 °C. The results further show that thermal creep of steel has a more significant impact on the behavior of shorter steel plates, whose buckling strength is governed by stability in the inelastic range.

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