Advanced numerical analysis of steel, concrete and composite structures under fire conditions

Abstract

High temperature in common fire causes changes in physical characteristics and mechanical strength of the materials used in the structures. In both steel and concrete, such characteristics deteriorate during the exposure to fire, and the structure load capacity and stiffness are reduced significantly with the increasing temperature. This work is on advanced analysis context of structures under fire, and it aims to develop a computational system for analysis of steel, concrete and composite structures in fire situation, based on the finite element method. The use of advanced analysis as a methodology of analysis/design of structures has various advantages. Among these advantages, there is the capture of strength limit and stability of a structural system and its members directly, without the need for separate verification of each member capacity. This provides a more realistic analysis and determine adequately the performance of a structure in a real fire. To achieve the objective, the CS‐ASA (Computational System for Advanced Structural Analysis) is used and expanded to advanced analysis of structures in fire situation, taking advantage of existing features and adding new ones. Two new modules were created: CS‐ASA/FA (Fire Analysis) and CS‐ASA/FSA (Fire Structural Analysis). The first aims to determine the temperature field in the cross section of the structural elements by FE thermal analysis in permanent and transient regimes. The second was created to perform the inelastic second‐order analysis of structures under fire considering the refined plastic hinge method coupled to strain compatibility method. The adopted numerical methodology is described and, for a more comprehensive validation of the implemented modules, various structural systems under fire are analyzed.