Non-linear hybrid homogenization method for steel-reinforced resin

Injected bolted connections have been used in the Netherlands since the 1970s, initially to replace riveted connections of steel railway bridges. More recently, structural components with different geometrical tolerances have also been connected using injection bolts and oversize holes. The natural confinement of a bolted connection provides support to the injected epoxy resin so that it can withstand bearing stresses that are significantly higher than its uniaxial compressive strength. A recent innovation in the field of injected bolted connections is the development of steel-reinforced resin, which consists of a skeleton of steel particles and a conventional epoxy resin (polymer). In previous research, the steel-reinforced resin has shown to increase the connection stiffness and decrease creep deformation significantly. In this paper, a hybrid analytical-numerical homogenization method, which can consider the plasticity of steel and resin, is proposed to determine the stress-strain relationship of steel-reinforced resins. The results of the hybrid homogenization method are validated against experimental data of small-scale specimen, subjected to compression in unconfined and confined conditions. Proposed hybrid homogenization method is an alternative to complex multi-scaling methods and allows for quick but accurate determination of mechanical properties of steel-reinforced resins.