Extension of the Continuous Strength Method to the design of steel I-sections in fire

Abstract

This paper presents an investigation into the extension of the Continuous Strength Method (CSM) to the design of steel I-sections at elevated temperatures. Structural response of 21375 high strength and normal strength steel I-sections at elevated temperatures is considered, taking into account a very broad range of cross-section geometries and cross-section slendernesses as well as different elevated temperature levels and steel grades which include both high strength S690 and S460 steel grades and normal strength S355, S275 and S235 steel grades. The implementation of the CSM for the fire design of steel I-sections is set out. The accuracy of the CSM against that of the provisions of the European structural steel fire design standard EN 1993-1-2 and its upcoming version prEN 1993-1-2 for the ultimate resistance predictions of steel I-sections at elevated temperatures is assessed. It is shown that in comparison to the elevated temperature cross-section design provisions of EN 1993-1-2 and prEN 1993-1-2, the CSM leads to a significantly improved level of accuracy and consistency in the ultimate strength predictions of steel I-sections at elevated temperatures.