Comparisons of Fire Resistance of RC Beams from Different Codes of Practice

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Title: Comparisons of Fire Resistance of RC Beams from Different Codes of Practice

Author(s): M.B. Dwaikat and V.K.R Kodur

Publication: Special Publication

Volume: 255

Issue:

Appears on pages(s): 125-146

Keywords: design codes; fire resistance; fire resistance standards; high temperature; reinforced concrete beams; restraint effect

Date: 10/1/2008

Abstract:
The fire resistance of reinforced concrete beams, computed as per three codes, namely, ACI 216.1, Eurocode 2, and AS 3600, is compared with that predicted from finite element analysis. A macroscopic finite element model, capable of tracing the behavior of restrained reinforced concrete beams from pre-fire stage to collapse, is used in the analysis. The model accounts for high temperature material properties, fire-induced strains (thermal, transient, and creep strains in addition to mechanical strain) and restraint effects as a result of fire exposure. Since restraint has a significant effect on fire resistance of reinforced concrete beams, the comparison is carried out for four cases of reinforced concrete beams with different boundary conditions. The first case represents a simply supported beam, while the other three cases represent axially restrained, rotationally restrained, and axially and rotationally restrained beams, respectively. Through the results of the case studies, it is shown that there is a large variation in the fire resistance predictions from the three codes, with Eurocode 2 being the most conservative and ACI 216.1 being the least conservative. It is also shown that the degree of axial restraint, rotational restraint, and type of failure criteria have significant influence on the fire resistance of reinforced concrete beams.