Load-bearing capacity of slender dowel-type fasteners of round ring-shank nails and U-shaped connectors (U-conn:s) of square cross-sectional nail thread used as connections in Timber-Concrete Composite structures have been studied, experimentally and with two different theoretical models. Tensile strength and withdrawal capacity of fasteners and embedment strength of timber were tested and evaluated. The parameters were used for calculation of the plastic hinge location in the fastener on the timber side and the load-bearing capacity of the connections. For this, both the European Yield Model known from the Eurocode 5, as well as a model where the load-bearing capacity is determined from mechanical equilibrium of fasteners in deformed state were used. Double shear push-out tests were carried out to determine the load-carrying capacity of the connections. The calculated values are compared to the experimental results. The models showed similar results for the U-conn:s regarding both plastic hinge location and load-bearing capacity. For the nails, all models show good correlation with experimental values, however, the model derived from the deformed state predicted both the plastic hinge location and the load-carrying capacity more accurately.