Chapter 3 - Loads and Dynamic Response for Offshore Structures

Abstract

This chapter discusses loads and dynamic response for offshore structures. For the convenience of structural analysis, vibration frequency analysis is also briefly outlined. This chapter concludes that the design of offshore structures is highly dependent on wave conditions, wave spectral shapes have significant effects on the fatigue life, choosing the best suitable spectrum based on the associated fetch and duration is required, the bandwidth parameter of responses is only dependent on the spectral period. It also concludes that the long-term approach is preferred when predicting extreme responses, because it has less uncertainty; however, using the long-term approach is recommended along with the short-term approach for obtaining a conservative result, the short-term extreme approach depends on the long-term prediction of extreme wave spectra and proper application of the derived wave spectral family. One of the key issues in the design of offshore structures is to define the environmental conditions for the transportation route and installation site, and to determine the environmental loads acting on the structure for conditions such as transit, installation, operational extreme, and survival. The aim of this chapter is to give an overall picture of the environmental conditions and loads for offshore structural design, and to detail the recent developments in the prediction of extreme response. This chapter discusses the environmental conditions and criteria for the design of offshore structures. In this chapter ,both long- and short-term wave data approaches are detailed. The basics of vibration analysis are also covered in this chapter.