Seismic

The objective was to conduct an international workshop on the design and requalification of offshore platforms. The workshop assessed the current state-of- the-practice and determined future research needs to close gaps in technology. The workshop discussed: methods used to make an assessment of the site seismicity and other characteristics of potential seismic sources;
methods used to predict strong ground motions, including the effects of basin geometry;
methods used to estimate the dynamic response of the structure/foundation/soil system to account for nonlinear effects; and

The objective was to assess the dynamic response of the operational areas (topside) of offshore structures subject to earthquake loadings. The study consists of three parts:

(1) an evaluation of the response characteristics of topside equipment under the combination of both seismic and operational loading,

(2) development of approximate methods to obtain the floor response spectra based on measured seabed motions, and

(3) development of a single approximate procedure for the seismic analysis of multi-degree of freedom and multiple-supported secondary systems.

This was a Joint Industry Project (JIP) consisting of the MMS and four industry participants. The objective of this study was to develop engineering guidelines to verify the holding capacity of a pile foundation for an offshore structure subject to a strong earthquake ground motions. The project simulated the response of axially-loaded piles in a specially designed test pit that allows actual data from recorded earthquakes to be used as forcing functions. The concern is if the seismic motion produces loss of capacity of the pile foundation during or after a period of strung-ground shaking.

This was a Joint Industry Project (JIP) with Tokai University in Japan to exchange information on soil/pile interaction models. The objective was to assess the reliability of current state-of-the-art soil/pile interaction models and their ability to predict the dynamic response of an offshore platform to actual earthquake loadings. The study will be used the seismic data collected from the Subsea Earthquake Measurement System (SEMS) being deployed in Project No. 68.

The objective was to obtain and analyze vibration data from selected offshore platforms using a system identification technique. This data will be used to develop an analytical model of the platform for a study of the dynamic motion of the structure subjected to earthquake loading. This project is being conducted concurrently with Project Nos. 68 and 125.