Experimental and numerical investigations of fire resistance of hybrid steel, concrete and timber slab

Abstract

This paper presents the results of a comprehensive study investigating the fire resistance of a novel steel–timber–concrete (STC) hybrid slab system. The research combines both an experimental approach to evaluate the structural performance of the STC slab under realistic fire conditions and a numerical approach to evaluate the thermal temperature gradients based on natural fire temperatures obtained from the experiment, Eurocode parametric curve (ECPC) temperatures, ISO 834 (International Organization for Standardization, 1999) temperatures and ASTM E119 (American Society for Testing and Materials, 2020). Experimental and numerical model parameters and specifications were informed by a baseline study on building designers and contractors utilising STC slab systems in Uganda, ensuring relevance to practical applications. A 4 × 3 m slab model was constructed, featuring a 75-mm concrete topping cast on an expanded metal lathe fixed to 100 × 100 mm Eucalyptus grandis beams spaced 600 mm centre to centre. These timber beams were simply supported on I-beams, which in turn were supported by SHS 75 × 75 x 5 mm columns. A natural fire scenario, as per Eurocode specifications, was implemented in a contained structure with burnt clay brick walls. The experimental investigation demonstrated that the STC slab could withstand a natural fire for over one hour while maintaining its load-carrying capacity. A numerical simulation was conducted using ABAQUS-CAE, a Finite Element Model program, to analyse the slab's response under both the experimentally obtained natural fire temperatures and the Eurocode parametric curve. The numerical results showed strong consistency with the experimental observations. Based on these findings, the STC slab successfully meets the East African code recommendations for an R60 fire rating, highlighting its potential for safe and sustainable construction.