CAPACITY OF GROUTED CONNECTIONS IN OFFSHORE
Monopile support structures have been used for many offshore wind-farms in typical water depths up to approximately 25 metres. The diameter of a typical monopile is in the range 4.0 to 5.5 metres. During recent years, the offshore wind industry experienced that the existing design methods for monopile to transition piece grouted connections did not result in an acceptable safety level, as evidenced by the unacceptable settlement of upper structures onto lower structures.
Two joint industry projects on capacity of grouted connections have been performed by DNV since autumn 2009.
In the first project it was shown that cylindrical shaped grouted connections without shear keys can no longer be recommended due to the low long-term axial capacity of such connections. A design methodology using conical shaped connections was developed to account for large dynamic bending moments on monopile structures. A second joint industry project on the capacity of cylindrical shaped grouted connections with shear keys subjected to alternating dynamic loading has been performed in 2011-2012.
This presentation will be a review of the industry practice relating to the design of grouted connections in offshore structures. The physical behaviour of the connections is explained and some of the most critical issues related to the design of large diameter grouted connections are presented. This includes results from laboratory tests and analytical work.
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Organizer - Society of Naval Architects and Marine Engineers Singapore, Centre of Innovation – Marine and Offshore Technology, Ngee Ann Polytechnic & The Joint Branch of the RINA and the IMarEST (Singapore)