Experimental investigation on thermal and mechanical behaviour of composite floors exposed to standard fire |
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Affiliation: | 1. School of Computing, Engineering and Mathematics, Locked Bag 1797, Penrith 2175, New South Wales, Australia;2. School of Engineering, University of Bradford, Bradford, West Yorkshire BD7 1DP, UK;1. 600 University Street, Suite 720, Seattle, WA 98101, United States;2. Robert L. and Terry L. Bowen Laboratory, Lyles School of Civil Engineering, Purdue University, United States;1. State Key Laboratory for Geomechanics & Deep Underground Engineering, CUMT, Xuzhou 221116, China;2. Key Laboratory of Building Fire Protection Engineering and Technology of MPS, Tianjin, 300381, China;3. School of Civil Engineering, Southeast University, Nanjing 210096, China |
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Abstract: | This paper presents experimental investigations on the thermal and mechanical behavior of composite floors subjected to ISO standard fire. Four 5.2 m×3.7 m composite slabs are tested with different combinations of the presence of one unprotected secondary beam, direction of ribs, and location of the reinforcement. The experimental results show that the highest temperature in the reinforcements occurs during the cooling phase (30–50 °C increment after 10-min cooling). The temperature at the unexposed side of the slabs is below 100 °C up to 100-min heating, compared to the predicted fire resistance close to 90 mins from EC4. For the slabs without secondary beams, the cracks first occur around the boundaries of the slab, while for the slabs supported by one unprotected secondary beam, concrete cracks first occur on the top of the slab above the beam due to the negative bending moment, and later on develop around boundaries. Debonding is observed between the steel deck and concrete slab. The secondary beam significantly impacts the deformation shape of tested slabs. Although a large deflection, 1/20 of the span length, is reached in the tests, the composite slabs can still provide sufficient load-bearing capacity due to membrane action. The occurrence of tensile membrane action is confirmed by the measured tensile stress in the reinforcement and compressive stress in the concrete. A comparison between measured and predicted fire resistance of the slabs indicates that EC4 calculations might be used for the composite slabs beyond the specified geometry limit, and the prediction is conservative. |
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Keywords: | Fire resistance Experimental investigation Composite floor Unprotected secondary beam Direction of rib Location of reinforcement EC4 |
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