Structural Behavior Analysis of Rail-Mounted Portal Cranes Equipped with a 360° Rotatable Spreader Mechanism Using the Finite Element Method

Abstract

Rail-Mounted Gantry (RMG) cranes are complex lifting systems widely used in container terminals and industrial sites to ensure the safe handling of heavy loads in both horizontal and vertical planes. One of the main subsystems of these cranes is the trolley , which operates in conjunction with the spreader responsible for carrying and transferring the load. In recent years, designs incorporating 360° rotatable spreader mechanisms have provided significant flexibility in load positioning but have also introduced complex stress distributions in connection regions. In this study, the structural behavior of the spreader component of an RMG-type portal crane was analyzed using the Finite Element Method (FEM). The investigation covered static, buckling, and fatigue strength assessments, with all calculations performed in accordance with DIN EN 13001-3-1+A2 and EN 13001-3-8 standards. During the modeling phase, the steel framework of the spreader structure, along with its welded and bolted joints, was represented in detail. Separate loading scenarios were established for different spreader configurations (rotated positions of 0°, 45°, and 90°), and lifting loads, wheel reaction forces, and boundary conditions were applied in compliance with relevant standards. The analysis results showed that the maximum Von Mises stresses remained below the material yield limit, and the fatigue strength in critical connection areas (such as drum plates, connecting bolts, and weld seams) satisfied the S6 stress range class requirements. Furthermore, the deformations observed in the spreader were within allowable limits, confirming that the structure possessed adequate rigidity against buckling. In conclusion, the RMG portal crane design equipped with a 360° rotatable spreader system was found to be structurally safe in terms of both static and fatigue performance, demonstrating compliance with international standards. This study contributes to the engineering-level optimization of spreader–trolley interaction in next-generation RMG crane systems.