A mechanism-based framework for predicting the horizontal capacity of multi-foundation systems under symmetric loading

Wind turbine installation vessels equipped with four spudcans are widely used in wind energy industry. While previous studies have predominantly focused on the combined bearing behavior of single spudcans, their response fundamentally differs from that of multi-foundation systems. In this study, centrifuge tests for wind turbine installation vessels under symmetric loading were conducted on both sand and clay. The results indicate that there are three failure modes of the wind turbine installation vessels under symmetric horizontal loading and highlighted significant load redistribution among the spudcans during the pushover phase. This redistribution led to the classification of spudcans into “loading” and “unloading” types. Based on this observed mechanism, the concept of a load transition state was formulated, serving as a key indicator for determining the ultimate horizontal capacity. Prior to the load transition state, the horizontal load was uniformly distributed among all spudcans. Furthermore, the ultimate horizontal capacity of wind turbine installation vessels can be predicted by analyzing the load paths of characteristic spudcans in relation to the failure envelope of a single spudcan.