STRUCTURAL RESPONSE OF STEEL AND COMPOSITE MATERIALS DURING FIRE
The aim of this project is to develop a structural response model for composite steel materials under fire and load conditions. The structural fire problem is made up of three distinct components - the fire, the consequent thermal load and the subsequent structural analysis.
Typically, these components are treated separately and linked by data passing between them. The model being developed by the FSEG attempts to treat the problem as a tightly coupled system and plans to use one software package for the entire analysis. The approach uses finite volume techniques to solve both the thermal and structural equations in a coupled manner, the structural model incorporating elastic/visco-plastic effects. Treating the beam as a continuum allows differential heating and temperature-dependent material properties to be examined in detail. The use of the finite volume techniques rather than the traditional finite element approach is a unique feature of this work. The first component to be developed is the structural response and heat transfer module.
The program calculates displacements, stresses and strains within the beam as a fire develops over a given time period. As a first approach, the beam is modelled in 2-D, as the project develops the analysis will be expanded to encompass a full 3-D approach. At each time step the temperature within the beam is calculated, thermal boundary conditions changing at each step. It is intended that these boundary conditions will eventually be predicted by the full fire field model. The temperature change within the time step can then be calculated and passed on as a loading to the routine which solves for displacements. Once displacements have been calculated stresses and strains can be determined. The program allows for temperature-dependent Youngs modulus and for composite materials and elasto-plastic behaviour. Results obtained from the program compare favourably with experimental data.
FIGURE CAPTION: COMPARISON OF TEMPERATURE AND STRESS FIELD PREDICTIONS IN TWO BEAMS, ONE UNPROTECTED AND THE OTHER PROTECTED BY CONCRETE.
Reference:
A.J.Camroux, E.R.Galea and C.J.Bailey. Structural response of steel and composite materials during fires. FSEG report 1995.
