Stochastic Parameter Estimation of Non-Linear Systems

Many mechanical and structural systems respond dynamically to random environmental loads, such as wind, wave or earthquake forces. Examples include flexible buildings vibrating due to turbulent wind loading and offshore structures moving as a result of combining wave and wind loading. To assess the reliability of such structures it is important to predict their dynamic response, at the design stage. However, whilst mass and stiffness parameters in the governing equations of motion can usually be computed with some accuracy, damping parameters are normally not quantifiable by theoretical means. For example, in the case of ship rolling in waves the appropriate parametric form of damping is well established. However, the damping arises from a very complex fluid-structure interaction between the waves and the ship motion, involving three dimensional vortex shedding. Thus, a theoretical determination of the damping parameters by the use of computational fluid dynamics technique is impractical.