Threaded rods grouted in beech laminated veneer lumber

Abstract

Glued-in rods are a class of adhesively bonded joints for timber engineering applications resulting in high-strength and stiffness connections. However, the use of polymeric adhesives may lead to issues related if the temperatures exceed their glass transition temperature, restricting their performance under quasi-static, or more critically, sustained loads. To overcome these, the substitution of polymeric adhesives by mineral high-performance grout was investigated. It was found that primers have neither a significant effect on strength nor on the failure mode; threated wood surfaces, however, resulted in a significant improvement of the latter. Based thereupon, grouted-in rods were manufactured. The best performance was achieved with a threaded wood surface, which achieved roughly 50% of the strength comparable adhesively bonded glued-in rod's strength. While the obtained strength may seem quite low, it is important to remind that the latter will largely remain unaffected by temperature; accordingly, made at room temperature, the comparison between grouted and glued rods is in favor of adhesive bonding, it may well be different at elevated ones.