This paper discusses the numerical modelling and simulation of Ferro casting ductile (FCD) metal shear key, or connector, without epoxy used for joining segmental precast concrete girders. In contrast to other types of cast iron, FCD metals exhibit higher level of ductility. In an effort to identify an optimum shape of an FCD metal shear key the numerical study in this paper investigates the response of four different geometries of full scale FCD metal shear key to shearing force from the concrete members and prestressing force acting in the centreline of the connector. Nonlinear finite element analysis of the shear key and the adjoining concrete members are conducted using ANSYS academic package. The appropriate constitutive relations for the FCD metal and concrete materials are obtained from test results and published values in the literature. The study considers two different magnitudes of prestressing force and two different concrete compressive strengths. Numerical results indicate that introducing a taper onto the forward ring plate of the Male part of the shear key results in a significant increase in its load-bearing capacity.