Chapter 20 - Spectral Fatigue Analysis and Design

Abstract

This chapter discusses spectral fatigue analysis and design. In the simplified fatigue assessment, the fatigue damage is estimated assuming that the stress follows a Weibull distribution for the long-term response. The fatigue analysis and design include several steps of analysis including fatigue screening, detailed structural analysis, reanalysis of welding improvements, reanalysis of design improvements, and reanalysis of design and welding improvements, etc. This chapter describes a fatigue analysis of floating structures, such as spectral fatigue analysis, including computer modeling, load conditions, structural analysis and validation, loading combinations, and fatigue damage assessment; time-domain fatigue analysis; and fatigue design of local structural details. This chapter explains that some terms applied in fatigue analysis have specific meanings. This chapter also discusses spectral fatigue analysis, including fatigue damage acceptance criteria and fatigue damage calculated using frequency-domain solution. Time-domain fatigue assessment is also made in this chapter. This section presents aspects of modeling, load evaluation, and structural analysis applicable to the overall structural analysis. These loading conditions include hydrodynamic loads due to waves, including dynamic pressure; inertial loads due to motions, etc. Symmetrical or asymmetrical load conditions are checked to confirm symmetrical or asymmetrical analysis results. This chapter also discusses fatigue analysis and design very effectively.