Preliminary comparative study on the behaviour of highly-loaded glue laminated timber and wood-CFRP composite beams exposed to local fire

Abstract

The paper presents a complex solution for testing loaded structural-sized glue laminated timber and innovative wood-carbon fibre reinforced polymers (CFRP) composite beams exposed to local fire. It shows the entire procedure from predicting a static behaviour and a combustion time (from reaching 300 °C temperature of the element up to its fracture) of the tested elements, designing and building an experimental stand, through conducting preliminary tests and discussing the results. The research included combustion of three glue laminated timber (BSH) and three wood-CFRP composite (BSH-CFRP) structural-sized beams in the most loaded section (region of highest bending moment) under three-point bending. A furnace was set under the centre of the beam on one-third of its span. The dimensions of the basket are based on physical properties of firewood providing proper burning conditions of the elements. The self-designed and self-constructed experimental stand enabled applying high load and provided a stable loading during local fire exposure. The preliminary tests showed that using CFRP tapes inside the section may both increase or decrease fire resistance of wooden members depending on the width of wood material covering CFRP tape. CFRP tapes provide a different nature of beam failure, which is changing from sudden fracture (BSH) to plastic flow of the material (BSH-CFRP).