Structural dynamics

Abstract

This chapter presents the basics of structural dynamics theory that is especially relevant to dynamics of flexible ocean structures. The primary focus herein is on linear structural dynamics, but the extension to nonlinear systems is also discussed. Section 37.1 introduces the singledegree- of-freedom, spring-mass-damper system. The equations of motion in the time and frequency domains are given, viscous and hysteretic damping models are discussed, and general solutions are provided. Topics of particular interest to ocean structures are discussed, followed by a discussion of numerical schemes for time-domain response. The generalization of these concepts to multi-degree-of-freedom systems is covered in Sect. 37.2. Hydroelasticity involves coupling the multi-degree-of-freedom, flexible structural model with the fluid model, such as used in Chap. 35, to obtain the coupled fluid-structure response. This is discussed in Sect. 37.3, in which the concepts of added mass and hydrodynamic damping are extended to the flexible structural model. Section 37.3.6 discusses the linear response to regular waves, and Sect. 37.4 extends this to random seas. Nonlinear hydroelasticity, viz. fluid-structure interaction, and corresponding solution strategies are discussed briefly in Sect. 37.5.