Research on dynamic characteristics of a tension-leg modular floating structure system under tendon failure

Abstract

Tension-leg modular floating structures (MFS) offer a promising solution for scalable ocean space utilization. However, these platforms may face potential tendon failure during operation, which can lead to severe instability. In this paper, a numerical framework is established to investigate the dynamic characteristics of a tension-leg modular floating structure system under tendon failure, using the ANSYS-AQWA user_force subroutine written in Fortran. Based on this foundation, a systematic analysis was conducted to examine the effects of single tendon failure and progressive tendon failures on motion responses, residual tendon loads, and connector loads under still water, regular waves, and irregular waves. The results indicate that tendon failure leads to adjustments in the modules' attitude and oscillations around a new equilibrium position, while its impact on the overall motion response remains relatively limited. Following the tendon failure, the residual tendon loads of the affected module increase significantly, and the connector loads between the affected and adjacent tension-leg modules are also considerably amplified. Due to the mechanical coupling effect of the connectors, the effect of tendon failure gradually propagates to other modules, causing minor transient responses and redistribution of tendon loads throughout the system, though the overall impact remains relatively small. In addition, an active ballast tank control strategy is proposed, which injects ballast water at the failed tendon location to adjust the module attitude and effectively mitigate the adverse dynamic responses caused by tendon failure. The results of this work provide valuable references for the design, operation, and failure prevention of tension-leg modular floating structures.