Critical temperature evaluation for laterally unrestrain steel I-beams in case of fire
Conference Paper
Overview
Overview
abstract
Fire resistance may be determined by simple calculation models applied to individual
members and should be based on safe results. This safety can be verified on three distinct
domains, such as, temperature domain, load bearing domain and time domain. The
temperature domain was chosen to show how a beam element might achieve the design limit
state by lateral instability, for a specified degree of utilisation.
A set of uncouple numerical simulations using ANSYS software will be presented, regarding
that mechanical deformation does not produce temperature change in the structural material
(no explicit creep is considered in the mechanical model). The thermal deformation, due to
temperature increase, is responsible for the introduction of mechanical stresses, which means
that first is necessary to define the fire and than, for each mechanical load increment, update
deformation field, under an iterative procedure (mechanical response model). The numerical
model is based on geometric and material nonlinearities.
The numerical tests use shell finite elements, with initial out-of-straightness and material
behaviour in accordance to the Eurocode 3. The beam element will be tested with two forks
supports and with a concentrated mid span dead load Q, with increasing temperature, based
on 800 [ºC/h] heating rate.
A set of results for different beam lengths will be presented and demonstrate that all critical
temperatures are greater than the specified value according to Eurocode 3. For critical
temperature validation, a set of experimental full-scale tests will be presented.
