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ABSTRACT This paper offers robust analytical equations and design configuration for finned piles based on the results of an extensive three-dimensional finite element analysis considering geotechnical and structural calculations. The expressions presented in this paper consider the influence that different aspect ratio of the caisson, fin configuration and soil characteristics, have on the finned pile response then enabling faster and optimised design process for developments in very soft deep-water clays. INTRODUCTION Suction piles for deep-water developments present a staple foundation solution. Owing to their excellent holding capacity characteristics in the combined V-H space, suction piles are deployed for a variety of applications, including holdback or hold down anchors for in-line pipeline structures and risers, mitigations against pipeline walking, or indeed for pipeline initiation purposes. The load for the applications mentioned above is usually transferred to the piles through the top plate (top loaded). There are occasions where to maximise the efficiency of the suction piles, the load is transferred via a padeye located at the side of the skirt as typically adopted for mooring piles of Floating Production, Storage and Offloading (FPSO) vessels. Depending on the application, suction piles may experience large magnitude horizontal loads, either arising from environmental conditions, operational loading from hydrocarbon circulation or infrastructure installation. Universities of Newcastle (UK) and Hamburg (Germany) started to investigate in the early 2000s how the addition of fins to the skirt can enhance the lateral response of suction piles, having the focus on windfarm foundations. Grabe and Duhrkop (2007) found a potential increase in lateral capacity from 10% to 60% as compared to a monopile where the optimal fin location was not at mudline. In addition, Durhkop and Grabe (2008) showed that any pile with fins has a stiffer system response as compared to a monopile, regardless of the shape and position of the wings. Subsequently, Peng et al., (2010) presented that for a monopile to provide the same resistance as a fin-enhanced pile, then the diameter of the monopile must exceed the core diameter of the finenhanced pile. Further salient findings can be found in Irvine et al., (2003), Grabe and Duhrkop (2007), Bienen et al., (2012) Duhrkop and Grabe (2009), Rudolph and Grabe (2013).
Lea, Michelle (General Dynamics Electric Boat) | Thompson, Donald (General Dynamics Electric Boat) | Blarcom, BillVan (General Dynamics Electric Boat) | Eaton, Jon (Pennsylvania State University) | Friesch, Juergen (Hamburg Ship Model Basin) | Richards, John (Hamburg Ship Model Basin )
Podded propulsion is gaining more widespread use in the marine industry and is prevalent in newer cruise ships in particular. This propulsion system can provide many advantages to the ship owner that include increased propulsion efficiency, arrangement flexibility, payload, and harbor maneuverability. A new, unique podded propulsor concept is being developed that allows optimization of each element of the system. The concept comprises a ducted, multiple-blade row propulsor with a permanent magnet, radial field motor rotor mounted on the tips of the propulsor rotor blades, and the motor stator mounted within the duct of the propulsor. This concept, designated a commercial rim-driven propulsor pod (CRDP), when compared to a conventional hub-driven pod (HDP), offers improved performance in a number of areas, including equal or improved efficiency, cavitation, and hull unsteady pressures. The combination of these CRDP performance parameters allows the ship designer much greater flexibility to provide improved ship performance as compared to that of an HDP. A CRDP is being developed to power a panamax-size cruise vessel. The paper addresses the hydrodynamic performance of that CRDP design demonstrated at 1/25th scale as tested at the Hamburg Ship Model Basin, Hamburg Germany (HSVA).
ABSTRACT: As against conventional columns foundations, coated columns can be used as ground improvement in very soft soils. The radial support is guaranteed through the composite between the geo-textile coating and the surrounding soil, while the geo-textile is under ring tension forces. Therefore this foundation system will be employed widely to found buildings, especially embankments on very soft or organic soils like peat. Numerical and analytical models for calculation and design of the new foundation system will be reflected. INTRODUCTION By the foundation of buildings on soft soils often an improvement of the soft soil with the already known column foundations was carried out for example compacted sand columns or vibro displacement granular piles. In very soft soils like peat this columns normally cannot be used, because the horizontal support in this soils is not sufficient. These columns are coated with a geo-textile of polyster threads, which guarantees the filter effect and the horizontal support. By using this new developed system a safe and flexible foundation on very soft soils with low settlements, especially for dams or traffic roads embankments, can be achieved. CONSTRUCTION PROCEDURE Two constructions methods are developed by the Josef Möbius Baugesellschaft GmbH, Hamburg, Germany, which are called the excavation method and the displacement method. By the excavation method a casing with a diameter between 0,8 m and 1,5 m is vibrated into the ground and after that the soil in the casing is excavated. Opposite to that by the displacement method a steel tube with a much smaller diameter of about 0,6 m to 0,8 m is placed into the subsoil. According to the displacement principle, the two base flaps of the casing are closed and displaces the soft soil to the sides of the casing.
ABSTRACT There are several chemical plants along the river Rhine that use river water as coolant in once through-systems. Microbially Influenced Corrosion (MIC) failures occur on stainless steel pipes and also in heat exchanger tubes coming in contact with this cooling water. This paper presents results of failure analysis of three case histories suspected to be caused by MIC. Afterwards several important corrosion engineering aspects are presented and discussed with respect to practical observations. Finally, a summary of the case histories and also some practical recommendations for MIC prevention in water handling units are given. INTRODUCTION Cooling of process equipment is one of the most important processes in the chemical industry. Usually natural waters like river or well water is used for this purpose. There are several chemical plants along the river Rhine in Germany (Figure 1) which use the water as coolant in once-through systems without any chemical treatment. The water distribution piping system for cold river water is commonly made of carbon steel. However, an increasing number of plants are using stainless steel (SS) for process equipment and piping systems. Figure 2 shows this trend comparing the annual demand of a variety of materials of construction used in the chemical industry. Looking at the results of a statistical investigation of failure analysis in a materials engineering department (Figure 3), one can see that stainless steel failures are over proportional to their use. A closer look at the cause of failures reveals that corrosion problems are the main contributor. MIC on stainless steel mostly leads to pitting and/or crevice corrosion, a type of failure which was observed in 200/0 of the failures. This value then defines the upper limit for MIC caused failures. Although the importance should not be underestimated a good estimate for the share of MIC related failures would be definitely less than 10YO. Based on three case histories, the paper represents an attempt to correlate observations made during failure analysis with basic corrosion aspects which have a mayor influence on the occurrence of pitting or crevice corrosion of stainless steels under abiotic and also biotic conditions. WATER SITUATION/SERVICE CONDITIONS In all our plants located along the river Rhine the mayor portion of water used is drawn off this river. However, each plant has different methods for taking and handling the water before implementation into their distribution net. In one plant, (Figure 4) the water is drawn off several wells after a natural filter process in the river bed and mixed with ground water taken from wells located at the plant area after a filtration process (e.g. removal of solids, Fe and Mn compounds). The average mixing ratio is nearly 90 0/0 Rhine river water and 10 0/0 groundwater. The chemical composition of the water used is presented in Table 1 with minimum and maximum values as well as average values for the different chemicals considered. The deposits on carbon steel pipes and the filtration units were chemical and microbiological analyzed. The results obtained are given in Table 2 through 4. In order to satisfy special interest for the microbiological methods used, see Table 5 and the description of the details elsewhere (1 to 11). The microbiological analysis were performed at the University of Hamburg, Germany (12). Determination of cell counts were done with the MPN- technique, dilution in 0.9?70 NaCl, incubation temperature 28 ?C, incubation time for tubes 3 weeks, for plates one week. The results can be interpreted that all species of bacteria are present, some with very high densities. As a summary it can be sta
SUMMARY EXACT studies of sediments are in many ways important for oil-mining. Prospecting for new deposits may be helped, as, in cases where index-fossils are scarce or wanting, key-beds may be defined by their petrographical character. In production, thorough knowledge of reservoir-rocks is. not only important in order to know what quantities of oil., are left in partly depleted fields to be recovered by new production methods, but also in starting new fields, well-spacing and production methods may be influenced. Also it may be hoped that such studies will contribute towards the solution of the questions of the origin of petroleum and the formation. of its actual deposits.' Porosity determinations alone are often not sufficient, as the size of the pores and the equal or different size of the sand grains too are important. During the past years, progress has been made in two directions-one by the mechanical analysis of the sands and the classification of their components by size, the other by mineralogical determination of specific heavy mineral components, extracted by means of heavy solutions. The author's opinion is that by mechanical analysis we get most familiar with the different conditions of the formation of sands and may best detect the influence of different mediums of suspension and deposition, highly responsible for the different character of sands. During the examination of drilling samples from' the Tertiary in the strata of Hamburg (Germany), the author could define and distinguish certain petrographical types of sands corresponding to different conditions of forma. tion, and also could show that the change of the mechanical composition in the subsequent samples and horizons along the profile obeys certain laws. Parallelisation of neighbouring hereholes is possible and is shown by profiles demonstrating the change of the average size of the grains in the formations. Diagrams are given demonstrating the different types of sands. In the same Tertiary beds others got interesting results by mineral examination. However, the author prefers mechanical analysis as a general start, as he expects by this work more information of practical value, especially also for production questions. In this connection it is cited that according to other publications it was possible, for instance, to separate and define three oil-sands of different geological age in Nienhagen (Hanover) by means of mechanical separation, while mineralogical tests in the same sands did not give dependable results. Zur Beantwortung vieler Fragen im Erdölbergbau vermögen genaue sedimentpetrographische Arbeiten wertvolle Beiträge zu liefern. Bei der Aufsuchung neuer Vorkommen, besonders innerhalb einer und derselben Lagerstättenprovinz, ist die genaue stratigraphische Einordnung eines einmal als Speichergestein angetroffenen Sediments und dessen sichere u