Experimental investigation of precast composite slabs subjected to natural fires
A new paper on fire tests of composite slabs has been published on “Construction and Building Materials”. Abstract: Precast concrete slabs have been widely used in modern construction as it alleviates the formwork through the lower precast section and provides uncompromised load resistance along with the in-situ cast upper section. However, very limited studies have been conducted to investigate such type of slabs in fires, especially in realistic fire scenarios. This paper experimentally studied the behaviour of four full-scale precast slab specimens subjected to the often-adopted standard fire curve and a natural fire curve representing realistic compartment fires. The slab configurations are also varied to represent the different precast approaches, which include the reinforcement of steel fibres and the use of precast joint strip. The test results have shown that a residential room fire could cause faster growing and larger deflections in the precast composite slabs in the first 30 minutes. The central deflection rate under residential fire could be up to 7 mm/min while the rate induced by standard fire was within 4 mm/min. The peak deflections induced by the residential fire were around 110 mm, which are lower than that of 162 mm induced by a 120-minute standard fire. It has been observed that the cracking patterns of precast slabs are similar to the flat concrete slabs according to previous tests, except the interfacial cracks due to the different stages of casting. A simplified numerical model has been employed to simulate the behaviour of these precast slabs, which could largely capture the deflections in spite of the discrepancies due to ignoring the precast interface and the details of steel bar truss.
