Experimental Investigation of the Dynamic Behavior of Welded-Plate Lifting Lugs for Hoisting Large-Span Steel Cap Beams

This paper systematically investigated the mechanical behavior of welded-plate lifting lugs subjected to dynamic and eccentric loadings in steel structure hoisting applications. By integrating on-site stress monitoring throughout the hoisting process with finite element numerical simulations, the dynamic response characteristics of the lugs were comprehensively analyzed. The results indicated that the stress response followed a three-stage evolution comprising elastic growth stage, peak fluctuation stage, and gradual decay stage. Non-uniform loading significantly intensified stress concentrations at the edges of the lifting holes and in the lug–stiffener transition region, with local impact parameters ranging from 1.02 to 1.12 and exhibiting a distinctly non-uniform spatial distribution. A refined finite element model was established, and comparisons with experimental data confirmed that static and dynamic prediction errors were controlled within 5 MPa and 5%, respectively. The optimal lifting angle of 75° was identified, resulting in a significant reduction in dynamic amplification. Furthermore, a small-sample Bootstrap method was introduced to probabilistically correct the dynamic parameter, enhancing design reliability by approximately 10%. Overall, this research provided a more rigorous theoretical foundation and practical design tool for evaluating the safety of lifting lugs subjected to dynamic loading.