Reinforcement for earthquake-damaged glued-laminated timber knee-braced frames with self-tapping screws and CFRP fabric

Abstract

Glued-laminated Timber Post and Beam Structure (GTPBS) is favored in timber engineering, primarily due to its commendable seismic resistance. Nonetheless, under severe earthquakes, these structures are susceptible to damage. This study aims to understand the impact of diverse reinforcement techniques on the lateral resistance of earthquake-damaged GTPBS. For this purpose, two full-scale frames were reinforced using self-tapping screws and Carbon Fiber Reinforced Polymer (CFRP) fabric before being subjected to horizontal low-cycle reversed loading tests. An in-depth comparison was made considering failure modes, hysteresis curves, and other pertinent parameters of the specimens both before and after reinforcement. Evidently, the employment of both self-tapping screws and CFRP fabric reinforcements curtailed the initiation and progression of joints cracks, averting premature structural failures. In addition, the better ductility of knee brace makes it more suitable for reinforcing earthquake-damaged GTPBS. These reinforcement techniques managed to recover over 90% of the bearing capacity of earthquake-damaged GTPBS, with a notable boost in their stiffness and ductility. The study culminates with an energy analysis that delves into the transformation and relative contributions of hysteresis energy and elastic strain energy during loading. From this analysis, it emerged that reinforcements using self-tapping screws and CFRP fabric not only ensure structural robustness but also maintain consistent energy dissipation.