Experimental study on the effects of scale on the static and dynamic behaviour of Glulam and hybrid-Glulam beams

Abstract

The research and development of timber and timber-hybrid systems depends heavily on the testing of large or full-scale structural components, which is often limited by laboratory space and budget constraints. Testing of small-scale samples is an alternative approach which can avoid costly experimental campaigns; however, little is known about evaluation of serviceability performance measures, including natural frequency and stiffness, which typically govern the design of elements in timber and timber-hybrid long-span systems. Downscale testing of timber is known to be susceptible to changes in material properties with size, the so-called ‘size effect’, but existing research into the size effect in timber focuses on strength rather than serviceability parameters. This work explores the effect of scaling down Glulam and hybrid carbon fibre (CFRP) reinforced Glulam beams, by comparing the dynamic and static performance of beams tested at both full-scale and approximately half scale. Outcomes of this experimental study indicate that serviceability parameters present small variations with scale, whereas strength parameters are affected by size effect in being consistently smaller in the full-scale samples when compared to their small-scale versions. It was also observed that tension-only reinforcement in hybrid CFRP–timber beams appeared to reduce the size effect in both static and dynamic parameters.