Abstract: In this paper, starting from the existing problems in the pile holding system of monopile holding equipment, the small stroke problem of the thrust cylinder is successfully solved through the design of the first generation step-by-step retractable beam system. Through the design of the second generation step-by-step retractable beam system, the composition of the first generation system is simplified, and the problem of thrust cylinder direct contact with the monopile is solved, which fundamentally solves the problem of possible damage of the thrust cylinder, and greatly improves the reliability of the system. Finally, the successful application of the step-by-step retractable beam system in practical engineering further verifies the reliability of the design.

Key words: step-by-step, retractable beam system, monopile, pile holding system, WTG foundation, thrust cylinder