Experimental and Theoretical Investigation of Steel-Cross Laminated Timber Composite Beams with Grouted Shear Connectors

Abstract

Embedded crush of timber surrounding shear connectors and high accuracy of bolt installation are two critical issues for steel-cross laminated timber (CLT) composite (SCLTC) beams with bolted connections. This study proposes novel grouted shear stud (GSS) connectors to overcome the abovementioned drawbacks. The shear performance of the GSS connectors was evaluated via push-out tests first and then four-point bending tests were performed to assess the flexural behavior of the SCLTC beams with GSS connectors. The test results indicate the GSS connectors mainly failed by shear yielding of studs and slight block rotation. The load-slip curves of the connectors were typically characterized by an initially linear-elastic response followed by a nonlinear ascending branch and a post-peak descending branch. The SCLTC beams mainly failed by local crush of CLT in compression and yielding of steel beam, indicating a pseudo-ductile failure mode. The load-midspan deflection curves of the beams were generally characterized by a bilinear response with an obvious yielding plateau. The initial composite action coefficient ranging from 83.5% to 95.9% indicates relatively rigid shear connectors were developed. The transversal strain of CLT slab was distributed in the shape of a saddle with edge strain higher than middle strain and termed negative shear lag effect. The finite element (FE) model validated by experimental results was employed for parametric analysis. Finally, a calculation model considering interfacial slip effects was developed to predict the full-range nonlinear behavior of the SCLTC beams. Good agreement was observed between the calculated results and the experimental data.