Abstract
To investigate the fire resistance of composite beams with restrained superposed slabs, three specimens were tested under uniformly distributed loads in a furnace. The effects of the thickness of the postcast top layer in superposed slabs and the spacing of shear studs on the structural behaviours of composite beams under fire were further examined. During the tests, the temperature distributions of the superposed slabs and steel beams as well as the displacements at their key positions were recorded and analysed. It was found that the temperature of the concrete superposed slabs decreased long their heights from the bottom. The most drastic change of the temperature along the slab cross section was found in the region with a distance of 40 mm to the slab bottom. The concrete superposed slabs could impose restraints to the steel beams due to their incompatible deformations. Cracks were developed on the top surfaces of the specimens and the superposing interfaces between the precast slabs and postcast top layers were not broken. Through the comparisons of different specimens, the spacing of shear studs could have a significant effect on the fire resistance of composite beams, especially for their deformation recovery capacities. In contrast, the effect of the thickness of the postcast top layers was negligible. ABAQUS was employed to simulate the temperature fields and deformation behaviours of composite beam specimens based on a sequenced thermomechanical coupling analysis. The numerical results agreed well with the experiment data, which validated the developed numerical model.
Highlights
Steel-concrete composite beams are composed of two main components including steel beams and concrete slabs
E British Cardington BRE Laboratory [1, 2] completed a series of fire tests on the composite beams with profiled steel sheet. e results showed that the catenary action could be developed if adequate horizontal restraints were provided for the composite beams
It was found that the shear connectors slightly affected the structural performance of the composite beams with profiled steel sheet, whereas the composite beams with flat slabs could fail due to the rupture of shear connectors
Summary
Steel-concrete composite beams are composed of two main components including steel beams and concrete slabs. Mirza and Uy [3] studied the influences of shear connectors on the fire resistance of composite beams through numerical studies using ABAQUS finite element software. E influence of different types of profiled steel sheet on the fire resistance of composite beams has been examined [9] and results showed that the contribution of the profiled steel sheet could be neglected for flexural strength calculation. Lyu et al [10,11,12,13] carried out fire tests on composite beams with flat slabs and found that the steel beam and the concrete slab could behave together with a better structural performance if a sufficient amount of shear connectors were arranged. The structural behaviours of three composite beams with restrained superposed slabs under fire are examined through experimental studies and numerical simulations
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