Critical Behavior of Long Span Cellular Beams in Fire

Abstract

This paper presents an investigation of the structural response of a long span cellular beam with varying section geometries while subject to various temperature-time curves. This type of beam is under investigation, in part, because of its increased use in long span building construction and its unique thermal response when protected with intumescent coatings; but more importantly, to provide an increased understanding into how these beams affect the surrounding structure in fire conditions. A nonlinear, finite element computational analysis of a steel-frame composite structure incorporating a long span cellular beam with a composite deck was examined to investigate local buckling behavior, midspan displacements, and connection forces of the long span cellular beam, and to compare the results with a similar I-shaped member with no web openings. This study appears to indicate that long span cellular beams exposed to fire experience two buckling events prior to undergoing large displacement behavior and catenary action. In addition, global and local response of these beams is largely controlled by local web stiffness particularly in pre-buckling behavior.