The Structural Engineer > Archive > Volume 90 (2012) > Issues > Issue 11 > Performance based seismic design of an offshore platform in the Caspian Sea
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Performance based seismic design of an offshore platform in the Caspian Sea

The development of gas fields in a highly seismic zone in the Caspian Sea required an innovative offshore platform. Arup were the detailed designers of a self-installing gravity based structure (GBS) to meet this demand – the first such platform to be commissioned in the region. Arup became involved after an elastic analysis based prescriptive design approach predicted the platform to have inadequate capacity to withstand signifiant seismic events. The Arup team adopted a performance based approach, in combination with advanced non-linear analyses, to demonstrate the suitability of the design for use in this location. Non-linear time history soil-structure interaction finie element analyses were used to demonstrate that the GBS platform satisfied the peformance requirements of ISO 19901-21. In addition, the performance based approach provided the client with an improved understanding of the likely response of the structure to a real earthquake and a greater ability to manage the risks associated with the facility.

Author(s): Rupert Gibson BEng, MSc, CEng, MIMechE Tom R Wilcock MEng, CEng, MICE Damian N Grant PhD, PE David A Gration BEng, CEng, MIMechE (All authors are with Arup, London)

Keywords: offshore platforms, gravity based structures, self installing, seismic design, iso 19901, finite element analysis, modelling, soil-structure interaction