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Creating a complete code for offshore concrete structures
Despite the fact that a number of concrete platforms are still in operation, particularly in hostile marine environments worldwide, there has been little development activity since the s. This is now changing with the renewed interest in robust concrete structures for the Arctic environment and for liquefied natural gas LNG storage.
The area is well known for icebergs, which is why the operators have found concrete to be the most competitive solution. Concrete solutions are also being considered for projects north and east of Russia and north of Norway, amongst others.
In the polar extremes, concrete structures are durable and robust to resist collisions with icebergs and are resistant to abrasion from floating ice.
They can also support heavy topsides and be designed to store oil. With a low lifecycle cost, concrete can reduce maintenance expenditure compared to steel solutions. Fixed concrete structures can provide continuous production and fewer shutdowns as they can withstand harsher weather. Unlike steel structures, concrete structures are built locally and therefore also promote the local economy.
Historically, operators used the former Norwegian concrete standards for offshore structures. This changed in when Eurocodes were adopted throughout Europe, including in Norway. The purpose of the Eurocodes is to provide a harmonised set of design and construction rules that are applicable throughout Europe.
DNV GL on offshore concrete structures | Energy Global
However, the Eurocodes focus on onshore structures and this has to some extent resulted in djv offshore experience being excluded. No other standard currently available to the industry covers the c5002 lifecycle of a concrete offshore structure and provides detailed design guidance.
To address the current offshore concrete developments, DNV GL is now reviewing the Offshore Concrete Standard to provide updates and new guidance, particularly for harsh locations. When it comes to designing offshore concrete structures, important effects that need to be considered are, for example, the concrete fatigue performance under water, effects of water pressure in pores and cracks and principles for watertightness.
In particular, submerged concrete does not perform as well as above-water concrete under fatigue loading.
This is believed to be due to the concrete degradation caused by cyclic varying pore water pressure and the pumping effect of water ingressing and exiting opening and closing cracks. Another interesting and unique feature of the updated DNV-OS-C is the systematics it provides for the qualification of new and innovative materials intended for offshore use. One of these materials is high-strength grout.
The standard has been developed on the basis of the experience DNV GL has gained over the years through its involvement in many offshore grouting projects. The approach defined in C ensures quality by considering all the aspects, from production to application, which are critical to the final in-place material offshore. Laboratory tests conducted by the material producer at an independent laboratory and witnessed by DNV GL are used to determine the fresh and hardened grout properties.
In addition, an audit of the manufacturing facility is undertaken with a focus on the quality control procedures in place for the product. A review of the offshore grouting procedure and quality control documentation is undertaken and forms the basis for the full-scale mock-up test performed to replicate the intended offshore application.
DNV GL believes that this type of certification scheme will facilitate the adoption of these materials by operators. Ultimately, the review of DNV OS C aims to create a unified consistent standard, covering the full lifecycle of an offshore concrete structure, that can be adopted by the industry.
Edited by Katie Woodward.
DNV-OS-C502 – Detailed Design of Offshore Concrete Structures – Draft
Read the article online at: This content is available to members only. Please sign in or become a member for free. Home Downstream Special reports 27 October Creating a complete code for offshore concrete structures. Concrete advantages In the polar ps, concrete structures are durable and robust to resist collisions with icebergs and are resistant to abrasion from floating ice.
Updated concrete standard Historically, operators used the former Norwegian concrete standards for offshore ow. Edited by Katie Woodward Read the article online at: