Evaluation of fatigue strength of high-strength grouted connections subjected to unidirectionally reversible cyclic loading

Grouted connections have been widely used in offshore construction to connect two different-sized cylindrical steel tubes; these connections include pile-to-sleeve grouted connections for mono-piles of wind turbine towers and pile-to-jacket-leg grouted connections for jacket structures. Because the grouted connections in seawater are mainly subjected to environmental loadings induced by waves and wind loading, high-strength grouted connections have been widely applied in offshore structures to enhance the structural performance and to prevent fatigue failure generated by the cyclic environmental loading. In this study, the fatigue performance of high-strength grouted connections with shear keys subjected to unidirectional reversible cyclic loadings in dry conditions was evaluated based on experimental tests, numerical evaluations, and comparative analysis based on a test database established using prior studies. It was revealed that the grout strength, shear-key density, and stress ratio have a significant influence on fatigue performance. Finally, general aspects of effects of grout strength, shear-key density, and stress ratio that influence the fatigue capacity of high-strength grouted connections were discussed, and a design equation for the unidirectional cyclic loading condition in dry conditions was presented.