Experiment and design approach of steel-to-laminated bamboo lumber screwed connections under load parallel to grain

As a new type of green building material, laminated bamboo lumber (LBL) has attracted more and more attention in the field of civil engineering. Dowel connections is one of the most significant connection methods for LBL, in which screw has the advantages of low cost and simple installation. This paper experimentally investigates screwed connections with LBL as main members and steel plate as side members, in which the effects of screw diameter, anchorage depth, end distance, center-to-center distance and row distance are studied. 45 single-screwed connection specimens were tested by symmetrically configured lateral resistance tests and 2 failure modes of screw pull-out and screw cut-off were observed, corresponding to 2 yield modes of screws. 18 double-screwed connection specimens were tested to propose design recommendations to avoid brittle failure between screw holes in LBL. Then the test results were compared with the predicted values calculated by NDS-2018, Eurocode 5 and GB/T 50005-2017. Based on the assumption of ideal elastoplastic model, a theoretical formula was derived and verified by test results. Besides, experimental load-slip curves were compared with those of Foschi model, which showed that Foschi model can be used to predict load-slip curves under the appropriate relative stiffness between fasteners and members. This research provides a scientific basis and favorable information for the engineering design and applications of LBL structures with screwed connections.