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ABSTRACT This paper presents results of the technological development of a rapid, automated pile splicer to be used in support of the Navy Modular Elevated Causeway System (ELCAS(M)). The ELCAS(M) is deployed to transfer equipment and supplies from ships moored offshore to any unimproved beach staging area. Rapid erection of the ELCAS(M) is essential in delivering the emergent vital logistics supplies to the Marine fighting units ashore during an amphibious operation. The results of ELCAS(M) exercises indicated that the system installation did not meet the mission time requirement. Several technological deficiencies may have contributed to the mission delays. The innovative automated pile splicing technology can reduce splicing time from the current 3 to 4 hours to less than 40 minutes per splice. This time savings represents a significant improvement since the splicing process is on the critical path of the ELCAS(M) installation. INTRODUCTION The Naval Facilities Engineering Service Center (NFESC), Port Hueneme, California, was tasked to develop the innovative technologies to improve the performance of the Navy Modular Elevated Causeway System (ELCAS(M)). Pile splicing is one of several technologies being undertaken to improve its splicing time and efficiency. The ELCAS(M) is deployed to transfer equipment and supplies from ships moored offshore to any unimproved beach staging area. Figure 1 shows a top view of a short version of the ELCAS(M). The Navy ELCAS(M) has an additional, non-military application it can be used to deliver emergency relief to people living in an area stricken by an earthquake, flood, typhoon, or hurricane. The system can be deployed to transfer a large quantity of containerized cargo consisting of food, water, gas, medicine, shelters, and other vital relief supplies to the beach from supply ships moored offshore.
- North America > United States > California (0.24)
- North America > United States > Virginia > Norfolk City County > Norfolk (0.15)
ABSTRACT A test programme was carried out in the small geotechnical centrifuge of the University of Delft to investigate the horizontal bearing capacity of suction piles in sand and clay. Thanks to the small size of the samples the soil density could be accurately reproduced, so that slight differences in design could be made visible. The influence of several parameters was tested, such as height/diameter ratio, the attachment point of the cable and loading angle. In some typical cases the failure mechanism was visualized in a three-dimensional test. The test results were compared with the API standard and with three-dimensional finite element calculations. It appeared that the optimum bearing capacity was achieved if the attachment point of the cable is at 2/5 of the pile height. The AP| calculations yield rather conservative values for the horizontal loads. The finite element calculations appeared to be in good agreement with the measured tendencies of the test results. It is believed that a combination of numerical calculations and tests in a small centrifuge yield a powerful design tool. INTRODUCTION In recent years, suction piles have been applied increasingly often in offshore engineering (Wang et al., 1978; Senpere et al., 1982). Suction piles are attractive because of the convenient method of installation. A pile with a diameter of 9 m and a height of 10 m can be installed in a few hours, by using a pump only. In a previous test programme (Allersma et al., 1997) the installation process was investigated by means of a centrifuge test. There was found to be a linear relationship between the pressure and parameters such as height, diameter and wall thickness. In this test programme the attention is focused on the static horizontal bearing capacity. In practice suction piles are used for several different loading conditions.
ABSTRACT A reasonable prediction of the short term axial capacity of a pile driven into a clay soil has major benefits in offshore applications. Therefore, a data base that consisted of 25 pile load tests were assembled and test results pertaining to measured pile frictional capacities after different intervals from driving were extracted and compared to predictions using current methodologies for the prediction of set-up effects. The results of these comparisons indicated a reasonable agreement between the measurements and the predictions made using simple relationships. It is shown that reasonable predictions can be made with current methods, with the inescapable drawback that in some models considerable judgement is required in the parameter selection. INTRODUCTION It is generally accepted that the "ultimate" capacity of a pile installed in a clay is achieved only after a substantial period of time has elapsed after pile driving. For the relatively large pile sizes used on offshore platforms, this period may take up to 1 to 2 years. In the "short term", however, a pile may have a considerably lower capacity than the long term value. It is also known that the gain in capacity, so-called set-up, builds-up fairly quickly during short periods after driving and slowsdown considerably afterwards, and so a large gain in capacity occurs within a short period of time from driving of the pile. The pile short term capacity and the potential gain in capacity are of significant importance in several offshore applications such as in deciding on the length of time between installation of the foundation and placement of the platform topside (hence pile loading), and in design of so-called docking or underleg piles. These are used in indexing of a jacket against a pre-installed template and/or to reduce mudmat requirements in soft seabed.
- North America > United States (1.00)
- Europe (1.00)
Abstract The Ursa Tension Leg Platform is located in the Gulf of Mexico in approximately 4,000 ft of water. The foundation design for the platform requires the installation of sixteen 96" diameter piles, each to be driven to a depth of 396 ft with an underwater hammer. The predicted hammer blow count necessary to achieve this design penetration resulted in driving fatigue damage becoming an important design issue. More than double the blow counts were expected for driving the Ursa piles than required for a previous deepwater project. This paper presents the methodology used in estimating the driving fatigue damages at the Ursa pile girth welds. First, pile driving stresses are generated by a pile driveability program. These records are then used in a simple one-cycle counting method to estimate fatigue damage based on Miner's rule. Second, the stress waves from the driveability program are used in a more comprehensive rainflow stress-cycle counting method based on Wirsching's algorithm. The selection of the design SN curve, along with the calculation of representative stress concentration factors, is discussed, and a revised thickness effect correction to the design SN curve is presented. The justifications for the selected design SN curve used in the fatigue damage ratio calculation and the allowable fatigue damage ratio, however, are not within the scope of this paper. 1.0 Introduction The Ursa Tension Leg Platform (TLP) is located, 130 miles southeast of New Orleans, in the Mississippi Canyon Block in the Gulf of Mexico in approximately 4,000 ff of water (Figure 1). The Ursa TLP foundation consists of sixteen 96" diameter piles with four piles at each corner of the TLP. Sixteen tendons (Figure 2) are to be directly connected to the tendon receptacles at the pile top, which is similar to the Mars and Ram/Powell TLP pile designs.
- North America > United States > Texas > East Texas Salt Basin > Shell Field (0.98)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Viosca Knoll > Block 957 > Ram Powell Field (0.89)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Viosca Knoll > Block 956 > Ram Powell Field (0.89)
- (9 more...)
ABSTRACT The New Pendulor test was proved to perform excellent survivability during 32 months sea test (1 st stage), but conversion efficiency was not high. The main cause was internal oil leakage of a vane pump developed for the Pendulor. In order to improve the efficiency, the Pendulor was studied again especially concerned with the vane pump, using the full-scale pump tested at sea besides using a model pump prepared for seal experiments. Applying the results obtained from the sea test (1 st stage) and the model experiment, the New Pendulor was re-designed and manufactured again. The Pendulor was installed in Aug. "98 at the same site where the former one was tested. In Oct. "98, the 2 nd stage sea test started. It was observed till end of Dec. "98 that the plant efficiency (motor output/incident wave power) was 40---60% around the rating power (output=5kW) condition. The pump efficiency was 60~80% that was 22–42% higher than the 1st stage. INTRODUCTION The authors invented a wave power converter New Pendulor. It consists of a pendulum and a large vane pump placed on the pendulum shat~ as a part of it as shown in Fig. 1. Incident waves become standing waves in the water chamber of which water flows reciprocally at the node. The pendulum is driven by the flow to be resonated with the significant water period "1"1/3. Pendular motion drives a generator via the pump and two oil motors combination. The profile of the New Pendulor has realized as a simple hardware of the system. The authors made a prototype one and tested it at sea for 32 months (Osanai et al 1996). The New Pendulor proved to have high survivability against so great storms, which have 10 times power of design rate.
ABSTRACT This work presents a methodology, based on computational simulation techniques, to predict the air-borne, structure-borne noise and mechanical vibration levels that will be imposed in Accommodation and Engine Room of FPSOs and Offshore Platforms. To predict the noise and vibration levels, information related to spectrum data noise and vibration of equipment, equipment arrangement, architecture, insulation and structure of the installation are used. The spectrum data noise and vibration of equipment were obtained from data bank or equipment manufacturers. The computational results allow identifying the areas where high noise and vibration levels will occur, by comparing these results with Technical Specifications. This procedure allows the identification of the most significant contributor to the final noise and vibration levels, the regions where limits are exceeded and what will be the most effective procedure to reduce them. Some practical recommendations to minimize the undesired noise and vibration levels are also presented at the end of the paper. OBJECTIVE Noise and vibration levels usually found in many FPSOs and Platforms, cause discomfort and health problems to their occupants. Correcting such problems of high noise and vibration in operating offshore plants are costly and production interfering. The objective of this paper is to show a methodology to calculate vibration, air-borne and structure-borne noise levels in Accommodation and Engine Room of offshore plants, during the project phase or in existing installations. The spectrum data noise and vibration of equipment are obtained from data bank or by information from equipment manufacturers. To predict noise and vibration levels some information are used, as equipment arrangement, architecture, insulation and structure of the plant. With the calculated results it is possible to identify the areas where high noise and vibration levels will occur and compare the results with the Technical Specifications.
ABSTRACT An assessment program for simulating the tidal flow and ecosystem in the sea around a very large floating structure or a Mega- Float, developed in the first phase of the Mega-Float project in Japan is presented. The model consists of two parts, a hydrodynamic model and a marine ecosystem. Tidal currents, water temperature, salinity and water density are calculated in a bay with/without a Mega-Float in the hydrodynamic model. A marine ecosystem model including nutrients, phytoplankton, zooplankton and organic matters has developed in detail. Simulation results with/without a Mega-Float of 4.75 km length, 1.5 km breadth and 1.2 m draft are presented in Tokyo Bay. Changes of marine environmental factors by the installation of the Mega- Float are studied for some configurations of a Mega-Float and breakwater. Lastly, some potential technologies for the environmental preservation and restoration are studied. 1 INTRODUCTION Predicting the marine environment changes caused by installation of a Very Large Floating Structure or a Meg.-Float is one of the technical challenges in introducing a Mega-Float into practical use. It has been known that the marine environment such as flow and ecosystem shows complicated changes due to a various natural conditions. So that on prediction of the environmental changes caused by installation of Mega-Float with precision, it is well recognized that the prediction of ecosystem changes including low-level planktons, organic matters and nutrients must be done after the prediction of 3-dimentioanl flow changes including wind driven current and density current due to thermal and salinity concentrations changes. In "An experimental Research of Very Large Floating Structure" by Technological Research Association of Mega-Float launched in 1995, researchers have been conducted studies taking these matters into account. It has been revealed through numeral calculations that the Mega-Float is expected to affect on the flow slightly 1)2).
ABSTRACT Suction caissons have emerged as an increasingly popular option for anchoring systems. To date, suction caissons have been limited to relatively low aspect ratios. However, as new offshore fields are developed in deeper water, higher aspect ratio caissons are needed in order to provide higher capacity, particularly in situations where a large upward component of load has to be withstood. Theory suggests that a limiting aspect ratio exists beyond which complete caisson installation cannot be achieved due to upheaval of the internal soil plug. This paper presents the data from a series of laboratory tests, aimed at establishing relationships between caisson penetration, installation pressures and volume of evacuated fluid and comparing results with the theoretical behaviour. Model caissons of various aspect ratios were installed in both normally consolidated and overconsolidated kaolin clay. The data exhibited excellent consistency but indicated limiting aspect ratios before plug failure that were somewhat lower than simple theory suggests. INTRODUCTION The exploration and development of offshore hydrocarbon resources in fields of increasing water depths has encouraged the evolution of a range of novel structures and associated anchoring systems. The focus of offshore foundation design has recently shifted towards the use of suction caissons due to their diverse application potential. Suction caissons have proved reliable under compressive and moment loading as a foundation for fixed jacket structures (Europipe and Sleipner, North Sea (Tjelta, 1994)), in pure tension to moor tension leg platforms (Snorre and Heidrun, North Sea (Fines et al, 1991)), and under the quasi-horizontal loads exerted by catenary anchored floating structures (N'kossa, Gulf of Guinea (Colliat et al, 1995)). The installation of suction caissons may be limited by structural and/or geotechnical mechanisms, the critical ones being lack of verticality, buckling of the thin walled caisson, or upward failure of the internal soil plug.
- Oceania > Australia > Western Australia > Timor Sea > Bonaparte Basin > Sahul Platform Basin > JPDA 06-103 > Laminaria-Corallina Fields (0.99)
- Europe > United Kingdom > Atlantic Margin > West of Shetland > Faroe-Shetland Basin > Judd Basin > Block 204/25 > Greater Schiehallion Field > Schiehallion Field (0.99)
- Europe > United Kingdom > Atlantic Margin > West of Shetland > Faroe-Shetland Basin > Judd Basin > Block 204/20 > Greater Schiehallion Field > Schiehallion Field (0.99)
- (13 more...)
ABSTRACT A unique temporary foundation system, which combined skirted mudmats with an air lift system, was used during the installation of two fixed offshore platforms. The skirts on the mudmats allowed the use of active suction to penetrate the mats. To optimize simplicity, reliability, and cost, water removal from inside the mudmats was achieved through the careful design of an air lift system using oil well gas lift technology. This skirted mudmat system has numerous advantages: it improves on-bottom stability of the structure, allows for a controlled initial penetration of the mudmats and provides a means to quickly and accurately level jackets. INTRODUCTION The Amoco Trinidad Mahogany "A" and "B" platforms are conventional 4 leg jacket structures with 4 skirt piles and are currently in place in the Atlantic Ocean approximately 50 miles (31 km) off the East coast of the island of Trinidad in approximately 285 ft (86 m) of water (Fig. 1). A unique temporary foundation system was utilized during the installation of these structures. This system provided a relatively high level of jacket on-bottom stability and permitted jacket leveling operations to take place at any time between jacket set down and the start of pile to sleeve grouting operations. Jacket leveling operations were accomplished with minimal installation vessel critical time and without hook assistance from the installation vessel. This system and its performance are discussed below. Platform Description Figure 2 shows two elevation views of the Mahogany "B" platform. The lift-installed jacket has mudline plan dimensions of approximately 100 x 100 ft (30 m x 30 m) while the top of the jacket is 50 x 100 ft (15 m x 30 m). The four main jacket legs are approximately 60 in. (1.52 m) in diameter. The topsides lift weight was approximately 3000 short tons (2700 tonnes).
- North America > United States (0.29)
- North America > Trinidad and Tobago > Trinidad (0.24)
ABSTRACT In this paper, the discharge capacity and the consolidation efficiency of the cross shaped drain are experimentally examined and compared with those of the band shaped drain. The equivalent diameter of the tested drains is back-calculated from the laboratory experiment and compared with those calculated from the formula suggested in the literature. The efficiency of the cross shaped drain is evaluated using the 3-D flow program, MODFLOW, which was validated by the settlementtime test fill data of Yang-San. The results of laboratory test show that the both drains with the same discharge area have quite similar discharge capacity and the consolidation efficiency, while the equivalent radius of the cross shaped drain was 22% less than that of the PBD with the same discharge area. The effective radius calculated from the Rixner's formula(1986) can depict closely the settlement-time data of laboratory tests. INTRODUCTION Nowadays Plastic Board Drains(PBDs) are usually applied instead of sand drain to improve weak clay sites and dredged soils of large clay fractions. Increasing the width of the PBDs to improve the discharge capacity seems not to be effective because it is again able to increase the diameter of the mandrels as well as installation spacing among the PBDs. The cross shaped board drain which was introduced by Pradhan(1996) and Kim et al.(1997) may be an alternative drain to be used to the large depth because it can have large discharge capacity by increasing the cross-sectional area of the drain without increasing the diameter area of the mandrel. It may also be used efficiently to the clays of shallow depth because the use of a cross shaped drain with the same width as of PBD would increase the rate of consolidation without changing the mendrel and the installation spacing.