| 種別 | paper |
| 主題 | Concrete for Arctic Oil Production Platforms |
| 副題 | |
| 筆頭著者 | Mark MAWHINNEY （Penta-Ocean Construction） |
| 連名者1 | Hiroshi SAEKI （Hokkaido University） |
| 連名者2 | Toshiyuki ONO （Hokkaido University） |
| 連名者3 | |
| 連名者4 | |
| 連名者5 | |
| キーワード | |
| 巻 | 11 |
| 号 | 2 |
| 先頭ページ | 709 |
| 末尾ページ | 714 |
| 年度 | 1989 |
| 要旨 | INTRODUCT ION Offshore oil platforms,as envisaged in Arctic areas where oil exploration is continuing,will need excellent durability and load resistance. Present experience supports the use of both steel and concrete,although the movement of ice and the extreme temperatures will impose severe structural loads and create many restrictions to normal working practices. It seems likely that an offshore production platform will require storage facilities as part of its design,and oil is typically stored at temperatures of between +50℃ and +80℃.This will cause elevated temperatures within the structure while outside,in mid-winter, air temperatures may drop to -50℃, with consequent large thermal gradients through the external walls,particularly at the waterline. By using typical values of stiffness,Poisson's ratio and the thermal expansion coefficient,Mawhinney indicated that theoretical thermal stress can be similar in size to wave and ice loading in fairly rigid members. This hypothesis required experimental support. CONCLUSION Within the confines of a limited experimental programme,the results indicate the interesting nature of concrete when subject to sub-zero gradients. With the help of previous work in related fields and use of finite element analysis it is possible to explain the diverse results,particularly the three dimensional nature of the thermal expansion. Normal density mass concrete follows the behaviour previously explained by Planas et al. In the context of this study,it is of purely academic interest since such a wall would not be employed in severe Arctic environments. Normal density reinforced concrete acts as a uniform body with constant thermal expansion coefficient and is the best of the specimens tested. However,the slow change in experimental temperature and consequent reduction in response require further consideration. The results of the lightweight concrete specimens are of considerable interest since it has already been used for offshore Arctic applications. The mid-section expansion would undoubtedly be a major design problem unforeseen by simple elastic theory,although it confirms the results of freeze-thaw studies. The specimens exhibit properties characteristic of a body where the steel and concrete are straining at different rates and in different directions causing disruption to matrix and bond. The analysis has concentrated on elastic behaviour although it is quite obvious that creep effects play an important role. In particular,the analysis of the results after the 12 hour stage may provide important clues to freeze-thaw behaviour patterns. The effects of other experimental limitations have already been briefly discussed. The problem of oil storage facilities for Arctic oil platforms requires further research. The provision of facilities below the waterline or sub-sea pipelines have an increased ice loading risk,while such facilities above the waterline cause large through wall stresses. Outer insulating 'buffer' zones such as used in the Super CIDS design or using new materials or design concepts will involve additional cost. Future research will need to identify suitable alternatives in design and establishing new standards. |
| PDFファイル名 | 011-01-2119.pdf |