ESTIMATION OF THE FOUNDATION CONDITION OF A FIXED PLATFORM BY MEASUREMENT OF DYNAMIC RESPONSE

Analyzes the recorded dynamic response of a Monopod platform in Cook Inlet and the simulated response with computer models in an attempt to discover the reason for observed changes in the fundamental frequency. A 3-dimensional linear dynamic structural analysis program modeled the recorded response to ice impacts and simulated model response to an assumed earthquake. A dynamic program and a non-linear finite-difference soil-pile analysis program were matched to model the soil-structure interaction. By varying model parameters it was found that for the Monopod, dynamic response was insensitive to changes in deck load mass or virtual water mass, but was strongly influenced by soil stiffness. By comparing numerical model output with recorded structural behavior, it was possible to estimate the condition of the soil and the pile foundation. This analysis revealed that the change in the fundamental vibration period was related to changes in the soil around the piles near the mudline. It was concluded that, for small deflections, the upper 20 feet of the soil does not contribute to the dynamic response of the soil-structure system. For the larger motions, associated with an assumed earthquake, this zone would contribute to dynamic response.

Media Info

  • Pagination: p. 65-74

Subject/Index Terms

Filing Info

  • Accession Number: 00138237
  • Record Type: Publication
  • Source Agency: Offshore Technology Conference
  • Report/Paper Numbers: V3, OTC 2625 Proceeding
  • Files: TRIS
  • Created Date: Sep 4 1976 12:00AM