Fire performance, including the cooling phase, of structural glued laminated timber beams

Abstract

Purpose Based on heating tests and load-bearing fire tests, this paper aims to discuss the charring rate, the temperature distribution in the section and the load-bearing capacity of structural glued laminated timber beams not only during the heating phase during a 1-h standard fire in accordance with ISO 834-1 but also during the cooling phase. Design/methodology/approach Heating tests were carried out to confirm the charring rate and the temperature distribution in the cross-section of the beams. Loading tests under fire conditions were carried out to obtain the load-deformation behavior (i.e. the stiffness, maximum load and ductility) of the beam. Findings The temperature at the centroid reached approximately 30°C after 1 h and then increased gradually until reaching 110-200°C after 4 h, during the cooling phase. The maximum load of the specimen exposed to a 1-h standard fire was reduced to approximately 30 per cent of that of the specimen at ambient temperature. The maximum load of the specimen exposed to a 1-h standard fire and 3 h of natural cooling in the furnace was reduced to approximately 14 per cent. In case of taking into consideration of the strength reduction at elevated temperature, the reduction ratio of the calculated bending resistance agreed with that of the test results during not only heating phase but also cooling phase. Originality/value The results of this study state that it is possible to study on strength reduction in cooling phase for end of heating, timber structural which has not been clarified. It is believed that it is possible to appropriately evaluate the fire performance, including the cooling phase of the timber structural.