Engineered wood products such as glued laminated timber (GLT) have been increasinglyused in high-rise buildings and long-span structures. GLT is more homogeneous and versatilethan solid timber, but it is still orthotropic, meaning its properties vary dependingon the direction of analysis. A drawback of this orthotropic structure is the relativelylow strength perpendicular to the grain direction, which, for high rise buildings and largespan structures, could lead to undesirable deformations of GLT members subjected tocompression perpendicular to the grain (CPG). In the working draft of the upcomingEurocode 5 (prEN 1995), a calculation model has been suggested when using self-tappingscrews to reinforce GLT beams against CPG. However, to reduce the carbon footprint,and to avoid collisions with embedded steel screws, an alternative method would be toreinforce CPG by means of adhesively bonded birch timber products, i.e., birch plywoodor birch rods.

The experimental studies in this thesis include uniaxial compression tests and indirectloading tests for both unreinforced GLT and GLT reinforced against CPG with birchplywood and birch rods. In total, 53 GLT members were tested in uniaxial compressionand 9 GLT members were tested in the indirect loading case.

Experimental results showed a significant improvement in compression strength perpendicularto the grain when using birch rods or birch plywood as reinforcement in GLT,compared to unreinforced GLT members. In uniaxial compression, the strength increaseranged from 120 % to 310 % for birch plywood and from 100 % to 470 % for birch rods,depending on the reinforcement method and amount of reinforcement. Moreover, testresults showed that birch rods had great consistency regarding the mechanical propertiesover the test series. Additionally, one 19 mm ∅ and 250 mm long birch rod achievessimilar strength capacity compared to a 9 mm ∅ steel screw of the same length. Thedifferent plywood methods showed varied results regarding ductility and consistency overthe test series. Assembling procedure and the contact surface of the loaded area provedto be important factors.

A capacity prediction model for reinforced GLT with birch rods and birch plywood isproposed in this thesis work. By taking the observed failure mode, i.e., compressionfailure of birch rods or plywood, into account, the predictions are in good agreement withthe experimental results. Other possible failure modes, e.g., buckling failure of the birchproducts, are not considered in the proposed model due to the face that they were notobserved during the tests. But they are of interest to be investigated in the future. Basedon the results in this thesis work, it can be concluded that both birch rods and birchplywood have great potential to become alternative methods for reinforcing GLT againstCPG.