Modeling of Composite Structures in Fire Using a Coupled Skeletal Frame and Floor System Analysis: Slab Panel Method

Abstract

This paper presents a proposed design methodology which combines the fire beam element (FBE) for skeletal frame analysis with the slab panel method (SPM) for floor experiencing catenary action. The methodology enables the two systems to interact with each other to provide a simplistic manner to design a full composite structure. The design methodology consists of an iterative process in which (1) the SPM is used to design the composite slab and provides the loads on the support beams of the skeletal structure, and then (2) the FBE analysis, implemented in OpenSees version 2.5.0, determines the deflection of the edge support beams which are used to update the SPM calculations. The existing two-dimensional (2D) FBE finite-element matrices are updated for a three-dimensional FBE, while the SPM is modified to allowing the interaction between the FBE analysis and the SPM. Three validation studies of the FBE analysis show that the FBE analysis is able to capture the behavior of the skeletal structure adequately, as long as the support edge beams of the slab panel have sufficient strength to support the slab panel. The application of the design methodology to an office building serves as a proof on concept and demonstrates that the deflection of the edge beams does have a significant impact on the predicted ultimate load-carrying capacity of the slab panel.