Experimental and numerical study on motion instability of modular floating structures

The parametric resonance, found in a single floating body, discloses that the kinetic energy could be transferred from heave mode to roll mode and causes motion instability if there is an integer multiple relationship between the two mode natural frequencies. For multi-module floating structures, the event of parametric resonance has not been investigated, but important for the stability and safety design of the floating platforms. In this paper, an experimental test is carried out using five box-type floating modules in a wave flume and observes the existence of the parametric resonance between the heave mode and roll mode. A mathematical model, validated by the experiment data, is built up for the theoretical analysis of the influential factors of the parametric resonance. The effects on the motion instability of wave condition, connector stiffness and number of modules are analyzed. It reveals that an appropriate stiffness setting of the connectors could eliminate the parametric resonance of multi-module floating structures. This theoretical finding is confirmed in a further experiment test on a five-module floating structure in the wave flume.