Moment-rotation model for steel-timber composite connections with slab continuity steel rods

Abstract

Detailed 3D nonlinear finite element (FE) analyses of steel-timber composite (STC) cruciform subassemblies including material, geometrical and contact nonlinearities are carried out. In the STC subassemblies, the steel beams are connected to the column flange by fin plates and/or double web-cleats and the continuity of the cross laminated timber (CLT) slabs across the column is preserved by mechanically anchored rods. The FE models are verified against experimental data and it is shown the adopted constitutive law of materials (i.e. steel and timber) and proposed modelling strategies accurately predict the failure mode, local (load-strain) and global (bending moment-rotation) response of the STC connections. Variables influencing the bending moment-rotation response of the STC connections are identified and considered in a parametric study and a mathematical model for the moment-rotation of the STC joints is developed by non-linear regression of the data obtained from the parametric study. The calibrated mathematical model is employed for blind prediction of the moment-rotation of the STC connections and the accuracy of the model compared to the detailed 3D nonlinear FE models is demonstrated by a few examples. Lastly, nonlinear FE analysis of a multi-storey STC frame with nominally pinned connections is carried out and it is shown that the continuity steel rods (anchored in the CLT slabs) reduce the mid-span deflection of the STC beams by approximately one-third.