The design model for inclined screwnails in timber-concrete composite beam interconnection

Abstract

Recently the methods of calculation of load-carrying capacity of dowel type connections are based on Johansen (1949) theory,which assumes the behavior of thematerial of connectedmembers and fastener as rigid-plastic. This assumption lets to determine the load carrying-capacity (yield load) very well for bolted or nailed connections, and only satisfactorily for screwnailed connections. This paper represents the model for screwnailed connections in timber-concrete composite beaminterconnection based on the theoreticalmodel of Kochenov (1953) by applying the additional equations for the embedding and withdrawal deformation of timber grain under the screwnail, as well, as the basic simplified equations for the design of such type connections. This model is based on more realistic behavior of element material, and on the limited value of embedding deformations of the timber under the fastener. The achieved theoretical results are verified in respect to performed experimental tests results obtained also by other researchers. Assuming the ultimate value for embedding deformation, the three basic possible failure modes are represented and the simplified model was developed. The developed design model allows calculating the load-carrying capacity as well as the corresponding deformation, and precisely evaluates the failure mode of connections.