Abstract
When multi-span RC elements are exposed to fire one usually observes a yielding of span cross-sections while a safety reserve of support cross-sections is still significant. Due to this phenomenon a redistribution of bending moments occurs and the values of sagging moment in span cross-sections decrease while the values of hogging moment in support cross-sections increase. This paper shows the results of tests conducted on two-span RC beams in a situation when only one span has been exposed to high temperature from the bottom. The beams were 12×16 cm in their cross-section. The length of the span was 165 cm. The load has been applied by two forces put on each span. The beams were made of C25/30 concrete with siliceous aggregate. As a result of significant stiffness decrease of the heated span, redistribution of shear forces and bending moment occurs. Due to this redistribution the tested beams were prematurely damaged due to exhaust of the shear load bearing capacity in the middle part of the beam span where there was no transverse reinforcement.
Highlights
Exposed to fire, reinforced concrete (RC) elements exhibit a significant reduction in load capacity and stiffness
In multi-span elements this phenomenon leads to redistribution of internal forces resulting in a reduction of sagging moments and an increase of hogging moments (EN 1992-1-2 2004; fib Bulletin 46 2008; Kordina 2010; Kowalski, Urbański 2013; Scott, Whittle 2005; Bednarek 2003; El-Fitiany, Youssef 2014; Dwaikat, Kodur 2008)
The main goal of this paper is to present an experimental study of the redistribution of shear forces and bending moments in two-span loaded RC beams, in case when, only one span is exposed to high temperature from the bottom face
Summary
Exposed to fire, reinforced concrete (RC) elements exhibit a significant reduction in load capacity and stiffness. This is caused by a decrease in the mechanical properties of concrete and reinforcing steel due to high temperature (EN 1992-1-2 2004; fib Bulletin 38 2007; fib Bulletin 46 2008; Colina et al 2004; Abramowicz, Kowalski 2005; Bednarek, Kamocka 2006; Hertz 2004; Kodur 2014). During fire the slabs or beams are usually heated only from the bottom face In this case only the tensile zone of the element (reinforcement) in the span region and the compressed zone in the support are heated. In multi-span elements this phenomenon leads to redistribution of internal forces resulting in a reduction of sagging moments and an increase of hogging moments (EN 1992-1-2 2004; fib Bulletin 46 2008; Kordina 2010; Kowalski, Urbański 2013; Scott, Whittle 2005; Bednarek 2003; El-Fitiany, Youssef 2014; Dwaikat, Kodur 2008)
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