Timber-Limecrete Composite Floors Using Timber Connectors Sloped toward or against Slip

Abstract

Building floors comprising timber joists connected to limecrete (lime concrete) slabs via timber headed studs have low carbon footprints. Such floors are not yet used owing to lack of underpinning research. This paper presents results from large-scale joint tests which show that by sloping the timber studs at 45° against the sense of slip so that the slab lifts off the joists during slip, not only does the joint exhibit good stiffness and strength, but also the joint fails in a highly ductile manner by double curvature hinging of each stud and by crushing of the adjacent limecrete and glulam near the slab-joist interface. With the studs sloped at 45° toward the sense of slip, joint ductility drops significantly while joint stiffness and strength rise dramatically. Test data are also given for a 4.6 m long timber joist-limecrete slab composite specimen with studs sloped at 45° against slip and loaded in four-point bending to failure. Nonlinear finite-element analysis (FEA) using the measured joint and material constitutive data is seen to reliably predict this specimen’s load response. The verified FEA is used to compare the effects of the two stud layouts on the specimen’s structural characteristics. An equivalent rectangular stress block is derived for the limecrete based on a polynomial fit of that material’s compressive stress-strain test data and assuming that the neutral axis of the timber-limecrete section lies in the slab. Finally, suggestions are made for future studies of this composite system.