Structural behaviour of steel-timber versus steel-concrete composite joints with flush end plate

Abstract

An innovative structural floor comprising of steel frames and cross-laminated timber slabs (i.e. steel-timber composite) has been introduced recently as a sustainable alternative to conventional composite floors with reinforced concrete slabs. To assess the structural performance of the steel-timber and compare it to steel-concrete composite and bare steel, push-down tests were performed on geometrically identical full-scale cruciform subassemblies with flush end plate connections. The width of slab and type of connections between the CLT slabs and the size of bolts connecting the flush end plate to the column were the variables in the testing program. The size of bolts and width of CLT slabs had minor (or no) influence on the hogging bending moment resistance. However, increasing the bolt size and CLT slab width increased the stiffness of the STC beam-to-column connections. Furthermore, the CLT-to-CLT connection type had significant influence on the stiffness and flexural capacity of the STC subassemblies under hogging bending moment. The results of the laboratory tests showed that the rotational stiffness and hogging flexural resistance of the semi-rigid STC joints with flush end plates are comparable to those of SCC joints. The ductility of the STC joints with a flush end plate is also comparable to identical SCC joints, providing that tensile failure in timber slabs can be avoided.