Research on Applicability of New Materials to Marine Structures in Tropical Climates: Exposure Test Project in Consideration of Actual State of Structural Members

The application of lightweight and durable new structural materials to structural members of marine constructions in harsh environments, such as marine oil production facilities, is expected to reduce their running/maintenance cost, thereby reducing their life-cycle cost. The subject of the present project of serial studies is to elucidate the applicability of new materials that are expected to be applicable to structural materials for marine constructions by focusing on their durability. To this end, exposure tests of these new materials are conducted in Okino-tori-shima and Miyako-shima, which are prominently fierce marine environments in Japan. The specific purpose of this study is to accumulate basic date that will contribute to the durability design of structures using these materials. In the previous series of studies conducted from 1998 to 2005, 22 types of new materials were classified into five corrosion grades based on exposure test results to assess their applicability as structural materials. The present study is conducted with more emphasis on their practical uses. In consideration of economic efficiency and practical utility, one each was selected as specimens from the five grades of structural materials: an aluminum alloy, stainless steel, 9% nickel steel, common steel, and CFRP (Carbon Fiber Reinforced Plastic). Structural members of actual marine structures are exposed to a corrosive environment while being subjected to the loads of their own weight and external forces. However, few studies have investigated the durability of materials under stress. The authors conducted literature searching in regard to the selected five materials but scarcely found study results or data publicly available that can be utilized for durability design. The authors therefore planned exposure tests in which test pieces were to be exposed to marine environments while being subjected to axial forces. The ongoing study began in 2006 and is planned to last for five years. This paper reports on the outline of testing and the results of preliminary investigation.