Experimental Evaluation of Steel‐Timber Hybrid Beams with Self‐Tapping Screws

Abstract

Mass timber has continued to gain popularity as a construction building material. One of the benefits of the material is its lower weight compared to conventional building materials. This lower weight results in smaller foundations and lower seismic demands. However, engineers designing mass timber floors add additional mass to the floors to meet stiffness requirements for serviceability limit states as well as seismic demands. As a result, many mass timber floors are being designed hybrid with steel construction such that steel members are used as horizontal gravity framing members and designed to be composite with mass timber floor panels. However, the connector used to create the composite action between the steel beams and girders and the mass timber panels has not been widely re‐searched at large‐scale. This paper summarizes a series of large‐scale direct shear tests using generic screws to develop composite action between the cross laminated timber deck and the steel girders. The goals of the experiment were to examine potential shear lag along the length of the beam that may develop under direct shear demands. The data from the experiment was analyzed for peak load carrying capacity of the connectors and slip modulus and compared with calculated design values from Eurocode 5. The results showed no evidence of shear lag effects. However, due to the highly nonlinear load slip behavior because of roping effects within the connectors, Eurocode 5 underestimated both the load carrying capacity and the slip modulus.