Mechano-sorptive creep, Glued Laminated Timber, Irish Grown Sitka Spruce, BFRP
The reinforcement of timber using fibre reinforced polymer (FRP) rods or plates is widely accepted as an effective method of increasing the strength and stiffness of members, while at the same time reducing the variability in properties. The short-term behaviour of these reinforced members is well understood. The long-term or creep behaviour has received less attention. Due to the hygroscopic nature of timber, creep is accelerated by moisture variations, the mechano-sorptive effect. In reinforced timber beams, the influence of the reinforcement and adhesive on the long-term response must be taken into account.
The objectives of the present work are to determine the durability of reinforced timber beams with respect to load duration (viscoelastic creep) and variable climate (mechano-sorptive creep) and to develop appropriate strength modification factors for design purposes. Sitka spruce is the most widely grown species in Ireland and is the timber used in this study. Glued Laminated (Glulam) beams are constructed from Sitka spruce and a proportion of the Glulam beams are reinforced with basalt-fibre reinforced polymer (BFRP) rods. The beams are loaded in bending and the effects of load duration and varying climate are being monitored. One sub-sample of the beams is being tested at constant temperature and relative humidity and a second sub-sample in a climate with varying temperature and relative humidity. This paper contains a description of the test set-up and presents the short-term MOE results for reinforced and unreinforced beams and the creep measurements from the first few months of testing.