ESTIMATION OF DYNAMIC CHARACTERISTICS OF DEEP OCEAN TOWER STRUCTURES

This report deals with the determination of structural dynamic parameters from field measurements of, say, platform motion. It is shown how actual response records can be used to estimate equivalent modal periods and equivalent total damping values. The proposed procedure is based on recent results which relate periods and dampings to the moments and the "partial" moments of the spectral density function of the structural response to wide-band excitation. Simultaneous records of the exciting forces (generated by ocean waves or by earthquake-induced motion of the ocean floor) need not be available. For cases in which only the first mode is activated, the proposed procedure calls for the computation of the first three moments (i.e., area, first and second moment) of the estimated response spectral density function in a frequency band which includes the fundamental frequency. The same method may also be used to estimate properties of higher modes in multi-degree-of-freedom systems by successively isolating portions of the power spectrum which contain higher mode peaks.

• Corporate Authors:

  Massachusetts Institute of Technology

  Department of Ocean Engineering, 77 Massachusetts Avenue
  Cambridge, MA  United States  02139
• Authors:
  • VANMARCKE, E H
  • Iascone, R N
• Publication Date: 0

Subject/Index Terms

• TRT Terms: Offshore platforms; Offshore structures; Reliability; Structural analysis; Vibration
• Uncontrolled Terms: Structural reliability
• Old TRIS Terms: Structural vibration
• Subject Areas: Bridges and other structures; Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00048379
• Record Type: Publication
• Source Agency: Massachusetts Institute of Technology
• Report/Paper Numbers: 72-12
• Files: TRIS
• Created Date: Nov 14 1973 12:00AM