Semi - Submersible (3 Pictures) 

Semi-Submersible Platform Houston, TX - December 2000 THANK TO  'E'  EXMAR ..// ===================   Contributed by: Otto DaSilva Exmar Offshore Company Stress Model: Exmar-2500 Semi-Submersible Deep Water Drilling Platform View the 7-second AVI movie (6.88 MB) This animated plot represents Exmar's design of the semi-submersible platform "Exmar-2500" for deep water drilling. The Original model used the SACS finite element package by Engineering Dynamics, Inc. (EDI.) The animation shows simultaneously three effects on the platform: Rigid body motion due to an extreme wave (wave height = 56 ft) coming from a 45 degree angle. Linear deformation on the model (amplified 75 times) resulting from the wave and inertial loading. Principal stress color contour due to the same wave and inertial loading. Using the Tecplot macro capability, the animation uses real and imaginary components of the wave and inertial loading to generate the deformation on the model and stress fields for the color contours as the wave passes through the semi -submersible. The animation helps to visualize the relationship between the deformation and stress distribution during the wave passage. These results are combined to other wave headings and frequencies to assess the structure integrity on extreme events and on fatigue failure modes.   ---==========---------------===============------------------  The sinking of the Sleipner A offshore platform Excerpted from SINTEF, Civil and Environmental Engineering: The Sleipner A platform produces oil and gas in the North Sea and is supported on the seabed at a water depth of 82 m. It is a Condeep type platform with a concrete gravity base structure consisting of 24 cells  and with a total base area of 16 000 m2. Four cells are elongated to shafts supporting the platform deck. The first concrete base structure for Sleipner A sprang a leak and sank under a controlled ballasting operation during  preparation for deck mating in Gandsfjorden outside Stavanger, Norway on 23 August 1991. Immediately after the accident, the owner of the platform, Statoil, a Norwegian oil company appointed an investigation  group, and SINTEF was contracted to be the technical advisor for this group. The investigation into the accident is described in 16 reports... The conclusion of the investigation was that the loss was  caused by a failure in a cell wall, resulting in a serious crack and a leakage that the pumps were not able to cope with. The wall failed as a result of a combination of a serious error in the finite element analysis and insufficient anchorage of the  reinforcement in a critical zone. A better idea of what was involved can be obtained from this photo and sketch of the platform. The top deck weighs 57,000  tons, and provides accommodation for about  200 people and support for  drilling equipment weighing  about 40,000 tons. When the first model sank in August 1991, the crash caused a seismic event registering 3.0 on the Richter scale, and left nothing but a pile of debris at  220m of depth. The failure involved a total economic loss of about $700 million. The 24 cells and 4 shafts referred to above are shown to the left  while at the sea surface. The cells are 12m in diameter. The cell wall failure was traced to a tricell, a triangular concrete frame placed where the cells meet. At right  one is pictured undergoing failure testing. The post accident investigation traced the error to inaccurate finite element approximation of the linear elastic model of the tricell (using the popular  finite element program NASTRAN). The shear stresses were underestimated by 47%, leading to insufficient design. In particular, certain concrete walls were not thick enough. More careful finite element analysis, made after the accident, predicted that failure would occur with this design at a depth of 62m, which matches well with the actual occurrence at 65m. Further information can be found in the series of reports available for purchase from SINTEF and in an article from Concrete International, August 1997, available online in an abridged version from Engineers Australia.                       ========================================================   Oil platform  From Wikipedia, the free encyclopedia   Jump to: navigation, search ExxonMobil's Beryl Alpha, located in the North Sea. An oil platform is a large structure used to house workers and machinery needed to drill and then produce oil and natural gas wells in the ocean. Depending on the circumstances, the platform may be attached to the ocean floor, consist of an artificial island, or be floating. Generally, oil platforms are located on the continental shelf, though as technology improves, drilling and production in deeper waters becomes both feasible and profitable. A typical platform may have around thirty wellheads located on the platform and directional drilling allows reservoirs to be accessed at both different depths and at remote positions up to 5 miles (8 kilometres) from the platform. Many platforms also have remote wellheads attached by umbilical connections, these may be single wells or a manifold centre for multiple wells. Contents [hide] 1 History 2 Types 3 Especially large examples 4 Maintenance and supply 5 Crew 5.1 Essential personnel 5.2 Incidental personnel 6 Drawbacks 6.1 Risks 6.2 Ecological effects 7 Tallest oil platforms 8 See also 9 References 10 External links ==-=-=-=-=-=-=-=-=--=-=-=-----=---   THE DEADLIEST ..WTACH THE....Hurricanes....     http://home.versatel.nl/the_sims/rig/i-hurricane.htmt   The deadliest.. http://home.versatel.nl/the_sims/rig/i-fatal.htm     click for rig incedents lists http://home.versatel.nl/the_sims/rig/losses.htm   The Most Expensive http://home.versatel.nl/the_sims/rig/i-expense.htm   First Blowout Desasters   http://home.versatel.nl/the_sims/rig/i-blowout.htm   Worst Colapse   http://home.versatel.nl/the_sims/rig/i-collapse.htm   Worst Sunk Rigs   http://home.versatel.nl/the_sims/rig/i-sunk.htm   Oorst Hurricane   Rigs Lost   http://home.versatel.nl/the_sims/rig/losses.htm   Links..   http://berkelyboatsales.com http://marinesource.com/bbs http://brisbaneboatsales.com   ALL ADDS  by GOOGLES...   THE DEADLIEST ..WTACH THE....Hurricanes....     http://home.versatel.nl/the_sims/rig/i-hurricane.htmt   The deadliest.. http://home.versatel.nl/the_sims/rig/i-fatal.htm     click for rig incedents lists http://home.versatel.nl/the_sims/rig/losses.htm   The Most Expensive http://home.versatel.nl/the_sims/rig/i-expense.htm   First Blowout Desasters   http://home.versatel.nl/the_sims/rig/i-blowout.htm   Worst Colapse   http://home.versatel.nl/the_sims/rig/i-collapse.htm   Worst Sunk Rigs   http://home.versatel.nl/the_sims/rig/i-sunk.htm   Oorst Hurricane   Rigs Lost   http://home.versatel.nl/the_sims/rig/losses.htm   Links..   http://berkelyboatsales.com http://marinesource.com/bbs http://brisbaneboatsales.com   ALL ADDS  by GOOGLES...