Glued-in hardwood rods as reinforcements for compression perpendicular to the grain: Single fastener to global loading cases

The accumulation of self-mass and the resultant permanent deformation are critical in the design of high-rise timber buildings, especially in the case of compression perpendicular to the grain (CPG). Metal fasteners, e.g., self-tapping screws, are conventional and standardized reinforcements against CPG in timber members. As a comparison, wooden rods provide a more environmentally friendly and cost-efficient solution. This study utilizes glued-in wooden rods and laminated densified wooden (LDW) rods as CPG reinforcements. Test series are first planned to characterize the single-fastener behavior by applying direct loading on the single rod. Thereafter, the global behavior of reinforced glulam specimens, following the loading of Case A and Case B as defined by prEC5, is investigated. All possible associated failure modes are observed and classified. The capacity and stiffness data are utilized to validate the proposed analytical loading mechanism of Case A. The number of glued-in wooden rods varied with the specimen geometry to investigate whether the effective numbers apply. Digital image correlation measurements were also performed on featured Case B specimens to visualize the stress dispersion and the reinforcing effect of the rods. Stiffness-related parameters are also discussed for all investigated specimens.