Read the text. Comment on the advantages and disadvantages of the floating welded mega-structures.

The idea of creating floating offshore structures of super-large dimensions, so-called floating mega-structures (FMS) originated and found its practical application in Japan. This is exactly where the greatest experience of construction of large floating structures has been accumulated, namely: ocean ships, offshore platforms, piers etc. Some of the largest floating structures are “Sea Giant” tanker - 440 m long, 58.8 m wide with 28.8 m draft and sea oil storage facility “Hiroshima” - 397 m long, 82 m wide with 25.5 m draft. Such huge facilities were mainly manufactured in shipbuilding yards in the docks or berths. Their dimensions were limited just by the capabilities of a specific fabrication. The idea of FMS was based on developing a structure of a much larger scale– up to several kilometer length. Such a task had no precedent in the world practice. In order to implement it (build the FMS and conduct full-scale testing of the proposed engineering and design solutions) 17 steel-making and ship-building companies of Japan formed in April, 1995 a Technological Research Association MEGA-FLOAT (TRAMF) that carries out the entire package of scientific, design, engineering and production developments.

Over the period of three years an experimental sample of FMS of 2x60x300m size was designed and built, which was followed by making in 1998 a three-year program, including investigations of various aspects of the problem of FMS development, in particular the possibility of their practical use. Investigation led to construction of a full-scale model of a floating airport. It was 1 km long, 120 m wide and 3 m high. The full-scale model was fitted with systems of instrument landing, landing beacons, glide-path system and other modern equipment.

A designed and manufactured full-scale model of 9500t weight and area of 8.4x10⁴ m² in the form of a box-shaped pontoon consisted of six modules, the largest of which was 383m long and 60m wide. The modules were primarily made of blocks, having longitudinal and transverse partitions, as well as a set of stiffeners covered with steel plates on all sides.

When modules were joined on the water surface, specific problems arose: ability to apply welding is limited by the level of modules; structures afloat develop higher deformation than on the ground; need to perform underwater welding; inability to provide setting in open sea. Therefore, the monitoring of the dimensions of a structure continuously is very important.

Computer application allowed determination of the optimal welding modes providing minimal linear error when extended welds are made, namely 30mm per 1000m of the weld. In addition, welding was performed at night to lower the level of deformations induced by temperature difference between the module underbody and upperworks heated by the sun. Depending on the depth the portable semi-automatic machines (“dry” welding near the waterline) or automatic machines (welding with local drying) of a special design were used.

As the anticipated life of FMS should not be less than 100 years, it was necessary to envisage all the measures to provide its reliability in service. Therefore, these following problems were addressed during the project: development of a system of optimal protection from corrosion; studying the ability to apply advanced materials; development of the technology of long-term monitoring; development of the technology for underbody repair.

5. Choose the topic and prepare your mini-presentation:

1. “Kinds and types of corrosion.”

2. “Application of electric welding in surgery.”

3. “The key-role of aluminium in welding.”

APPENDIX

1. Improving phonetic skills.

Read, translate, and learn:

Limericks.

There once was a student named Bessor Whose knowledge grew lesser and lesser It at last grew so small He knew nothing at all And today he’s a college professor.	There was a young cannibal called Ned Who used to eat onions in bed His mother said “ Sonny It’s not very funny. Why don’t you eat people instead?”
There was a young lady of Niger Who smiles as she rode on a tiger They return from the ride With the lady inside And the smile on a face of a tiger.	There was a young lady from Gloucester Whose parents thought they had lost her And at last she was found From the fridge came a sound The trouble was how to defrost her.
There was a young girl from New York Whose body was lighter than cork She had to be fed For six weeks upon lead Before she went out for a walk.	There was a young lady called Perkins Who was awfully fond of small gherkins One day for her tea She devoured forty three And pickled her internal workings.
A gentleman dining at Crewe Found quite a large mouse in his stew Said the waiter: Don’t shout, Or wave it about, Or the rest will be wanting one too!	There was a young man called Paul Who grew so exceedingly tall When he got into bed He could stretch out his leg And turn off the light in the hall.
There was an old woman from Kent Whose nose was remarkably bent One day they suppose She followed her nose And nobody knows where she went.

Дата добавления: 2015-11-16