Experimental behaviour and numerical modelling of timber-timber composite (TTC) joints

Push-out tests were conducted on 15 groups of symmetric timber-timber composite (TTC) joints with coach screw shear connectors. The push-out test results were used to characterise load-slip, peak load carrying capacity and failure mode of the composite shear connection between timber slab made of cross laminated timber (CLT) and timber beams/joists made of laminated veneer lumber (LVL) and/or glued laminated timber (GLT). Effect of coach screw size, type of engineered wood product (i.e. LVL-to-CLT and/or GLT-to-CLT), GLT grade, thickness of the CLT slab and orientation of load with respect to the outermost layer of CLT on the structural behaviour of the TTC joints were studied. In addition to the TTC connection tests, embedment strength of the LVL, CLT and GLT and bending yield strength of the screws were experimentally determined and the results were incorporated into a versatile nonlinear beam on inelastic foundation finite element (FE) model to capture the full range load-slip response of the TTC connection. The nonlinear FE models (including material and geometrical nonlinearities) were validated against the test data produced in this study and available in the literature and it was shown that the proposed nonlinear FE model can accurately predict the load-slip, stiffness and peak load carrying capacity of the TTC joints with screw shear connectors. The ultimate strength of the TTC joints were also estimated by modified European yield model (EYM) and comparison of the experimental peak load with EYM and FE predictions demonstrated the significant influence of the rope effect on the full range load-slip response and ultimate load carrying capacity of the TTC joints with dowel shear connectors. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study conducted push-out tests on symmetric timber-timber composite joints with coach screw shear connectors and developed a nonlinear finite element model to accurately predict the load-slip response. The results demonstrated the significant influence of the screw shear connectors on the ultimate load carrying capacity of the TTC joints.