Deformation diagram and slip modulus of timber-concrete nailed connection

The common type of ties in hybrid timber-concrete structures are nails (bolts, screws, etc.). In the design of structure the connection work is taken into account through the composite action coefficient, which in its turn depends on the slip modulus. According to the current standards [2], the calculation is based on the assumption of linear elastic behaviour of the connection, while experimental studies have shown that the deformation diagram has a clearly expressed nonlinear character. Besides, the calculated slip modulus differs significantly from the one obtained from test results. Thus, taking into account the actual nature of the operation of the compounds makes it possible to obtain more accurate calculation methods. The purpose of the article is to develop the theoretical relationship for determining the slip modulus of the nailed connection of hybrid wood-concrete structures. Conclusion. Based on the analysis of existing data on the features of the deformation of the nailed connections of hybrid timber-concrete structures, an equation is proposed for the dependence of the slip modulus of the connection on the displacement. It was revealed that the application of linear-elastic behaviour models in the calculation of timber-concrete connections leads to overestimated values of the bearing capacity.The theoretical deformation diagrams obtained correspond to the experimental ones and more accurately reflect the beaviour of the connection under load in comparison with the current design standards. The theoretical values of the slip modulus are 30-35% less than the experimental ones, which is satisfactory taking into account the heterogeneity of the physical and mechanical properties of timber and to ensure the reserve of bearing capacity. The proposed dependence for determining the slip modulus allows taking into account its change during connection operation under load.