Numerical Analysis Of The Eurocode Assumptions For Temperature Distribution In Composite Steel And Concrete Beams.

Abstract

The design of composite steel and concrete beams should normally include the
progressive deterioration in strength and stiffness of its components (steel section, concrete
slab and shear connectors) with temperature rise under fire. In European Prestandard
Eurocode 4, a simple calculation method is described where the assessment of the composite
beam strength consists of two different steps: first the calculation of temperature distribution
versus time in the cross-section and then the determination of the mechanical behavior to
estimate the load-bearing capacity of the member.
In this work, a study is described to verify if the simplifications allowed by Eurocode 4 to
obtain the temperature rise in the components of composite beams comprising steel beams
with no encasement may lead to inappropriate design. Two programs were developed for the
analysis: the first, a heat transfer code, for the determination of the temperature distribution
in each region of the composite beam; the second, a structural analysis program, for
designing the composite beam. As an example, a composite beam has its positive bending
moment strength determined under the temperature calculated numerically as well as the
temperature obtained with the simplifications. The strength results are compared and
discussed.