Rankine Approach for Fire Resistance of Axially-Restrained Steel Column

摘要

It is expensive to predict the critical temperature of steel columns within a frame under fire conditions using the standard fire resistance test. Numerical approximation using the finite element method assumes the availability of non-linear visco-elasto-plastic software. As an alternative, theoretical analysis that can be performed manually is a convenient tool for engineers to quickly assess the column fire resistance. In this paper, traditional Rankine formula is extended to predict the critical temperature of an isolated restrained steel column. A linear spring attached to the column top end accounts for the axial restraint of the surrounding structure on the isolated heated column. Both the axial restraint and creep strain are incorporated into the Rankine formulation. Extensive comparisons between the predictions of Rankine approach and FEA show that under different external load and boundary restraint levels, Rankine approach yields accurate and slightly conservative predictions.