Bending behavior and bond analysis on adhesively bonded glulam-concrete panels fabricated with wet bonding technique

In this paper, we report on the effect of adhesive type on the bending behavior of adhesively bonded glulam-concrete composite panels. Steel-reinforced and unreinforced concrete were bonded to glued-laminated timber (GL-24 h) panels with polyurethane (PUR) and epoxy adhesives using the wet bonding technique. The PUR and epoxy adhesives (both were two-component adhesives) were selected to represent brittle and ductile adhesive behaviors. Four-point bending load was applied to glulam-concrete composite panels to investigate their bending behavior. The bending behavior measured includes bending load vs. mid-span deflection, strain distribution at the mid-span of the panel, and strain distribution between the loading point and its adjacent support. These were determined by linear variable differential transformers (LVDTs), strain gauges, and digital image correlation (DIC) technique. The experimental results showed that polyurethane-bonded glulam-unreinforced concrete panels showed similar load vs. mid-span deflection curves to epoxy-bonded glulam-unreinforced concrete panels and epoxy-bonded glulam-reinforced concrete panels. The shear stress, shear deformation, and peel strain analyses at the adhesive bond line showed that debonding at the glulam-concrete interface was more likely to occur for panels bonded with the ductile polyurethane.