Simulation of Stochastic Ice Force Process of Vertical Offshore Structure Based on Spectral Model

摘要

The action of drifting ice floes may induce strong vibrations of offshore structures,and further reduce the structural safety and serviceability.The aim of this paper is to develop a method by considering ice crushing as a stochastic process.On the basis of ice force spectrum which considers the time and spatial correlation between the local ice forces,a simulation methodology to generate the stochastic ice forces process of vertical offshore structure is proposed.The crucial segment in the simulation is to accurately calculate the effective ice pressure,and it is accomplished by an empirical formula which can provide a high calculation accuracy.Considering the effect of incidence angle and tangential ice force,global ice force spectrum is established,and the synthesis of the local ice force is realized.The presented simulation methodology is conducted on the Norstr?msground lighthouse to verify its efficacy.The results show that the simulated maximum global ice forces are close to those measured data,and the frequency contents of the generations coincide well with the target.They directly proves the validity of the proposed simulation method.Compared with the traditional methods,such as field measurement and ice force identification,the present simulation method has advantages in the application range.It can be used to simulate the stochastic global ice force for an arbitrary width offshore structure.In addition,it can also be used for extreme ice force analysis and dynamic response analysis of offshore structures.