Hollow‐core concrete slabs exposed to fire

Abstract

SUMMARYThe aim of this paper is to provide recommendations to designers and to propose a simple method for designers to model the structural behaviour of hollow-core concrete (HC) floor slabs in fire. The proposed finite element model incorporates a grillage system using beam elements to capture the thermal expansion of the precast units in both directions, with the topping concrete over several precast units modelled by shell elements. The research reported herein compares the proposed model with various fire test results of HC slabs. The simulation outcomes show good agreement with the experimental results.Several HC slab flooring systems tested previously at the University of Canterbury for seismic purposes were simulated using this modelling scheme. Various supporting schemes have been considered, and the results show that different arrangements of axial and rotational restraint at the supports can significantly influence the fire performance of the concrete slab floors.

Effect of Aspect Ratio on Fire Resistance of Hollow Core Concrete Floors

“…Nevertheless, the model considers the prestressing effect, the thermal strains as well as the mechanical stresses induced by incompatible thermal strains in both lateral and longitudinal directions, and the continuity between the hollowcore units which subsequently allows the model to take account of the effects of the end and side supports. Most importantly, the results from this modelling method showed good agreement with experimental results available in literature 4 . The model developed in the previous study worked well for small subassemblies.…”

“…Chang et al 4 have showed that SAFIR can successfully predict the performance of hollowcore floor systems in fire by using a grillage of 3D beam elements to simulate the hollowcore units and a layer of shell elements to represent the topping concrete slab which covers the hollowcore units and connects the hollowcore units to each other and to the surrounding structural members.…”

“…Structural behaviour of hollowcore concrete floors is dominated by action parallel to the units and their prestressing strands. Two-way action can sometimes occur in such slab systems, resulting from transverse structural behaviour of the topping concrete, depending on the vertical supports parallel to the hollowcore units [1][2][3][4] . The fire resistance of hollowcore concrete slab has not been outlined specifically in Eurocode 2 5 .…”

“…Since conducting experiments to study the effect of aspect ratio of hollowcore floors is very expensive, and also because previous study 4 has successfully predicted the fire performance of hollowcore concrete floor systems with different end and side connections using the non-linear finite element program SAFIR 6 , numerical modelling of hollowcore concrete floor systems is carried out to study the effect of aspect ratio on the fire performance of hollowcore concrete slabs.…”

Modelling the Fire Resistance of Prestressed Concrete Floors using Multi-Spring Connection Elements

“…Previous studies [11] have modelled the floor slabs with beam or shell elements whose end nodes share the nodes of the beam elements representing the supporting beams. This is acceptable for cast-in-situ or precast flooring system without prestressing, but leads to a major problem for precast prestressed flooring systems where the steel tendons terminate at the end of the flooring units, because the approach of sharing nodes of the supporting beam and floor assumes that these tendons are anchored into the supporting beams.…”