Research Status of Connection Joints of Laminated Bamboo Beams and Calculation Theory of Perpendicular-to-Grain Loading

Abstract

Laminated bamboo is an engineered bamboo material with broad application prospects in building structures; however, the connection joints of laminated bamboo beams are prone to brittle splitting failure under loads perpendicular to grain, which threatens structural safety. This paper systematically reviews the research status of laminated bamboo beam connection joints and the calculation theories for perpendicular-to-grain loading. The research status is summarized from two aspects: beam–column connection joints and beam–beam connection joints, covering the failure modes, influencing factors of the load-carrying capacity, and strengthening methods (self-tapping screws, carbon fiber sheets, steel hoops, prestressed steel straps, etc.) of steel side-plate and slotted-in steel plate bolted connections. The calculation theories are also reviewed in two categories: the yield capacity theory based on Johansen’s yield theory, including the capacity formulas of slotted-in steel plate and steel side-plate connections under the European yield modes, and the splitting capacity theory perpendicular to grain based on fracture mechanics, including the linear elastic fracture mechanics model of Van der Put, the non-linear fracture mechanics model of Jensen, and its modified model. The results show that current research mostly focuses on the mid-span joint load form, while the beam-end support joints (steel side-plate–dowel supports) that bear shear-dominated loads have been studied less; moreover, the existing models are mainly established for timber with the joint located at the beam mid-span, so their applicability to the support joints of laminated bamboo has not been systematically verified. Therefore, research on the applicability evaluation and modification of the splitting capacity calculation models perpendicular to grain is needed, so as to provide reliable calculation methods and a theoretical basis for the safe design of bamboo structure joints.