Geotechnical

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) to update the results of an earlier study (Project No. 105), on the feasibility and cost of transporting oil and gas from potential discoveries in the Chukchi Sea. The two modes of transport considered were pipelines and tankers, as well as combinations of the two. The update followed the methodology in the original study, but incorporated the results of the environmental and operating data collected in the past five years since the initial study.

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.

This was a Joint Industry Project (JIP) to evaluate methods to predict the capacity of drilled and grouted (D&G) piles. The use of underwater hammers in deep water is expensive and it may not be possible in water depths greater than 2,000 feet. This makes a driven pile foundation unattractive or not feasible. An alternative is to use drilled and grouted piles which can be placed by a drill ship. One problem associated with D&G piles is that their capacity can not be checked as easily as that of driven piles where the pile driving record is an indicator of pile capacity.

The objective was to study, by simulating realistic conditions in a centrifuge, earthquake ground motions and the effects on the soil-structure interaction phenomenon for offshore structures. Such studies will lead to better methods for: (1) developing site-specific seismic design motions, (2) determining liquefaction potential and permanent ground movement, and (3) predicting pile behavior for different earthquake ground motions.

The objective was to evaluate the current state-of-knowledge of multiple large-diameter piles (spuds) as an effective part of the foundation system for gravity structures in the Arctic. A literature survey was performed and analysis was conducted to investigate the sensitivity of critical design parameters for spud pile foundations. Analytical tools for spud pile design were evaluated and recommendations for design guidelines were made.

This was a Joint Industry Project (JIP), to extend the wave force simulation techniques developed under Project No. 2 to include directional wave spreading, shallow water effects, and a general analytical method for the time domain simulation of any specified wave spectrum. The new techniques will aid in determining the structural fatigue life of a structure and will improve the ability to predict their dynamic performance.