FS-Offat-Spec is a series of program modules that interface with FS2000 for the spectral fatigue analysis of framed structures under cyclic loading due to the action of hydrodynamic waves.

Outline Procedure

• FS-Wave - WaveLoader steps a characteristic wave through the structure.
• The drag and inertia components of load are processed to obtain equivalent harmonic nodal loading
• FS2000's Dynamic Response Module is used to obtain the dynamic response to the harmonic loads
• SCF Evaluation - SCFs evaluated at up to 12 circumferential locations (stress points) on brace and chord side.
• Stress Range - Peak stress range evaluated at all stress points for the stepped wave (employs static improvement technique)
• Transfer Functions - Stress range tranfer fucntion created by using waves with different wave periods
• Wave amplitude spectrums used to describe a random seastate eg JONSWAP
• Spectral Stress Response Spectra obtained from transfer functions and seastate spectra
• Scatter Diagram- Directional wave exceedence data defines by user specified scatter diagram.
• SN Curves - Standard SN curves or user defined curves are used in conjunction with Miners Rule to evaluate damage ratios.

Simple Operation

All Modules run in batch mode. A control file utility program creates all load cases and control files used in the fatigue analysis.

• Joint Recognition - Automatic recognition of Chord and Brace members
• Classification - Automatic Joint Classification (T/Y, K, X etc) based on geometry. Gap evaluation for K joints.
• Non-Tubular Joints - Stress ranges at standard nodes using defined SCF.
• SCF Evaluation Utility - Automatic SCF evaluation based on program evaluated parameters and SCF category. Evaluation utility for sensitivity studies on SCF parameters.
• UEG · Kuang, Wordsworth/Smedley
• DEn Guidance Notes
• DNV/API/EC3/ISO 1434 Ethymiou Parametric Equations
• User Defined Re-Classification

All program evaluated parameters including SCFs may be re-defined using user defined classifications and parameters.

• SN Curves - Standard or user defined curves.

Selective Output

• Graphical - Damage Ratio Plots Selective plots - Show only low lives
• Sorted Summary - Sort by Life Rating
• Restricted Output- Limit Output to Defined Criticality Limit (Life threshold)