Introducing a novel diagram-based method for shear design of steel plates at high temperatures

It seems necessary to develop a simplified design approach in order to evaluate the shear strength of web panels under fire condition as the size of furnaces is limited, the cost of experiments aimed at testing the fire resistance of structures is quite high and access to simulation software packages such as ANSYS and ABAQUS is not always guaranteed. In this paper, web panel shear design relationships of AISC360-16 and AASHTO-14 specifications are exploited to be used in fire conditions. To this end, the stress-strain reduction factors provided in EN 1993- 1-2 are directly applied. Afterwards, the design curves are proposed for prediction of the ultimate shear strength and limiting temperature of steel plate girders under fire by taking into account the strength degradation caused by high temperatures and the effects due to sectional instability. According to the results, the proposed curves are more accurate in compact plates with plastic shear buckling at both ambient and high temperatures. However, by increasing the web slenderness, the difference is increased. At ambient temperatures, the maximum difference for compact, noncompact, and slender web plates is about 1.1%, 23%, and 28%, respectively. The difference at 400 C0 reaches to almost 3% and 7% for non-compact and slender web panels, respectively. In addition, at 600 C0, especially for slender plates, proposed curves yield values that are nonconservative for ultimate shear strength such that the difference is about 11%. Also, the maximum difference for existing experimental and numerical studies is about 20% and 4%, respectively.