However, a circular cross-section with a relatively small diameter was not the optimal solution for the transition to the square topside. That reduces wave forces acting on the platform and thereby allows its base section to be reduced, as well as securing a more efficient design. The conical shaft in the Draugen GBS has its narrowest diameter at the sea surface, where it measures just over 15 metres compared with more than 22 metres down at the storage cells. The jacks are constantly adjusted to adapt the formwork to the desired shape of the concrete wall and to correct possible variations without exceeding tolerances specified in the chosen building standard.Ĭareful control of shaft geometry is exercised with the aid of laser measurements to ensure that all dimensions meet the tolerances throughout. Adjusted to the curing time of the concrete, the speed of the glide will vary with complexity and volume and is normally 1.5 to four metres per day. Illustration: Norwegian ContractorsĪs concrete is cast, the whole formwork get raised by activating the jacks simultaneously. sirkelens kvadratur, engelsk Sketch showing the principle of "slipforming". If the design requires changes in diameter, the formwork radius can be adjusted with a horizontal jacking system. Other tasks here include pouring concrete into the forms, applying epoxy, inspecting the finished result and repairing possible surface blemishes.įormwork and gangways are attached to frames hung from hydraulic jacks, which move up as the structure rises. Gangways are installed on both sides of the wall around the whole circumference to provide a work space and access for such jobs as installing reinforcement bars (rebars) and cutouts. The actual formwork comprises a vertical sheet installed to ensure that wall thickness and shape meet the design specifications. Slipforming was the best approach for the big concrete GBSs because it permitted continuous construction with few joints and cost-efficient working.įigure 2 shows how this is typically built up. The method is advantageous where many cutouts – such as windows – are involved. Such cases involve a limited number of disassembly/reassembly operations. That approach is preferred when constructing vertical sections of limited height, such as in residential properties or foundations. It can then be reinstalled to cast the next section. This was a special form of a “climbing formwork”, where a form is constructed and then disassembled once casting has been completed. A technique known as “gliding formwork” or “slipforming” was used to construct the vertical sections of the concrete gravity base structures (GBSs) built in Stavanger and elsewhere.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |