Elastic method for design of 3-D steel structures subject to fire

• Published in: Journal of constructional steel research Vol. 60; no. 7; pp. 1095 - 1108
• Main Authors: Wong, M.B., Szafranski, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2004
• Subjects: Elastic analysis; Fire engineering; Force interaction; Limiting temperature; Space frames; Steel; Force interaction; Limiting temperature; Space frames; Steel; Fire engineering; Elastic analysis
• ISSN: 0143-974X; 1873-5983
• DOI: 10.1016/j.jcsr.2003.09.002

The elastic method previously developed for the design of steel structures subject to a fire for a 2-dimensional framework has been extended to a 3-dimensional one. In the method for a 2-dimensional framework, only bending about the major axis is a primary condition for design consideration. In this context, the deterioration of the bending moment capacity of a steel member subject to increasing temperature is related to the elastic bending moments attained due to the actions of both the static loading and the thermal loading. The relationship can be established for each member in terms of the unknown limiting temperature which can be solved. The lowest of the limiting temperatures of all members is the critical one for the whole structure. In extending this design method to a 3-dimensional framework, failure criteria beyond pure bending are used to appropriately reflect the state of force interactions in the members. This approach is reasonable as, in reality, structural members in a 3-dimensional framework are subject to different forces attributable to their ultimate failure at increasing temperature. In this paper, axial-bending interaction, including bending about both axes, is adopted as the failure criteria although other failure criteria, if required, can easily be incorporated into the design. In the examples given, it is shown that the limiting temperature of the structure decreases as the complexity of the failure criteria increases.