Development and application of a simulation approach for fire and structure interaction of concrete members subject to spalling

Abstract

Summary This paper describes the development and illustrates the use of an approach to model the mechanical performance of a concrete bridge and its structural components exposed to fire and subject to spalling. The work is motivated by some recent fire incidents that involved concrete bridges, the poor state of an increasing number of bridges throughout the United States (which makes them more vulnerable to fire damage), and the lack of design codes and standards that adequately protect bridges against fire. An important objective of the work is to develop a method to predict spalling that captures the principal physical and chemical phenomena but is simple enough so that it can be implemented in a 3‐D structural simulation. The first step in the approach involves using a hydrothermal model to determine if and at what temperature spalling occurs for a specified concrete mix (defined by its composition, type of aggregate, water‐cement ratio, porosity, permeability, etc), free moisture content, and heating rate. The second step uses the resulting “critical spalling temperature” in a coupled thermal and mechanical analysis to determine how spalling affects the performance of the concrete member. The approach is illustrated for two standard fire resistance tests conducted on posttensioned concrete slab systems reported in the literature. The paper concludes with a list of recommendations for additional work to improve the predictive capability of the heat and mass transfer and structural models and to address several challenges with the implementation of the spalling criteria in the structural model.

Advancements in evaluating the fire resistance of structures

“…After stringent peer review, 12 of the 17 oral presentations are presented here as full papers. The papers accepted for this issue were on the following topics[5][6][7][8][9][10][11][12][13][14][15][16] :Due to modern developments in the construction materials industry, to ensure design safety, we are being challenged with requiring significant understanding of new materials and their performance in fire. Since 1918, the standard fire time-temperature curve has been utilized to assess the fire resistance of building materials.…”

“…After stringent peer review, 12 of the 17 oral presentations are presented here as full papers. The papers accepted for this issue were on the following topics: Comparative Energy Analysis from Fire Resistance Tests on Combustible vs Non‐combustible Slabs The Discrepancies in Energy Balance in Furnace Testing, a Bug or a Feature? A New Test Methodology for Studying the Response of Walls to Real Fire Environments Simulating Real Compartment Fire Conditions in a Furnace Rectification of “Restrained vs. Unrestrained” Fire Resistance of Cold‐formed Steel Framed Shear Walls under various Fire Scenarios Development and Application of a Simulation Approach for Fire and Structure Interaction of Concrete Members subject to Spalling Test Methods for Characterizing Concrete Properties at Elevated Temperatures Evaluation of Standard and Real Fire Exposures on Thermal Response of Rail Car Floor Assembly Best Practices for Modeling Structural Boundary Conditions Due To a Localized Fire Flame Extension and the Near Field under the Ceiling for Travelling Fires Inside Very Large Compartments An Extended Travelling Fire Method (ETFM) Framework for Performance‐based Structural Design …”