Fire damage assessment of reinforced concrete bunker with composite fire protection coating

Purpose This study investigates the thermo-mechanical behaviour of a reinforced concrete (RC) bunker subjected to fire and evaluates the effectiveness of a composite fire protection coating in mitigating fire-induced structural deterioration. Coating efficiency is characterised by its ability to reduce the temperature rise and restrain the development of concrete stress, reinforcement stress and lateral displacement to acceptable levels and to prevent compression damage in concrete within 30 min of fire exposure. The study also aims to establish the minimum coating thickness required to maintain structural safety and serviceability under fire exposure. Design/methodology/approach A three-dimensional finite element model of an RC cuboidal bunker with a trapezoidal hopper was developed in Abaqus. A transient coupled temperature-displacement analysis was carried out for a 30-min external fire curve as defined in Eurocode 1. Three analysis situations were considered, i.e. ambient conditions, one-sided heating and bottom heating. Seven coating thickness arrangements were studied for a composite fire protection system of heavy gypsum board and rockwool insulation. Structural performance was evaluated based on temperature distribution, stresses in concrete and reinforcement, lateral displacements and concrete damage. Findings The post-fire exposure concrete stresses, reinforcement stresses and lateral displacements show an increase, exceeding the ambient temperature limits prescribed by IS 456:2000. Different thicknesses of composite coating decreased the peak temperatures in the range of 93.31–96.50%. Minimum coating thicknesses of 4 cm and 6 cm were required for one-sided and bottom-fire exposure scenarios, respectively. Stresses, displacements and concrete damage remained within acceptable limits with such coating thicknesses. Originality/value The research is one of the first system-level fire assessments of a complete RC bunker and gives performance-based minimum thickness requirements for a gypsum–rockwool composite fire protection coating for different fire exposure scenarios.