DNV GLs Offshore Technical Seminar

Prediction of Air Gap and Horizontal Wave Impact Loads for Column Stabilised Units

Technical Seminar

Training Information

  • Date:

    February 1, 2017

  • Time:

    9:00 am to 3:00 pm

  • Location:

    DNV GL Office, 1400 Ravello Drive, Katy TX 77449

  • Cost:


On December 30th, 2015 while operating on the Troll Field in the Norwegian North Sea, a column stabilised drilling unit was hit by a steep wave with direct impact on the forward port side of the deck box.  The incident resulted in one causality and four injured with 17 broken windows and permanent deformations to the front bulkhead of the unit.  The accident has revealed that horizontal wave loads to the deck box structure can occur from large steep waves lower than the maximum design seastates (e.g. seastate with 100-year return period).  These loads have not been adequately considered in current industry standards, analytical tools and practices or model tests.

In response, DNV GL has published new technical guidelines DNVGL-OTG-13 and DNVGL-OTG-14 to deliver a consistent and updated approach for calculating air gap and horizontal wave impact loads for column stabilised Units.  Although the current OTGs are more relevant for harsh environment, some of the challenges and lessons learned from the incident and the OTG development can also be relevant for other regions, e.g. Gulf of Mexico. 

Overview of DNVGL-OTG-13 and DNVGL-OTG-14:
The air gap of a column-stabilised unit is defined as the vertical distance between the underside of the deckbox and the wave elevation. Negative air gap will occur if the wave elevation is higher than the underside of the deckbox. In case of negative air gap, possible slamming loads needs to be accounted for to the bottom plating and/or vertical bulkheads of the deckbox structure. The objective of DNVGL-OTG-13 guideline is to define a recommended procedure for estimating air gap for column-stabilised units in compliance with DNVGL-OS-C103.  The object of DNVGL-OTG-14 is to provide a guideline for the loads to be used to document structural and floating integrity of MOUs that are subject to horizontal wave impact with the deck for the design conditions in compliance with DNVGL-OS-C103.

 Please join DNV GL’s Offshore Technical Seminar – Prediction of Air Gap and Horizontal Wave Impact Loads for Column Stabilised Units.  This seminar will provide insight into the newly issued DNVGL-OTG-13 – Prediction of Air Gap for Column Stabilised Units and DNVGL-OTG-14 – Horizontal Wave Impact Loads for Column Stabilised Units.  Participants will learn the background for the new guidance, the changes to current practice and the impact to operating units.

For technical questions, please contact the following:
Jenny Lu 63
Jenny Lu
Head of Section
Hull & Structures
+1 (281) 396-1866

Heather Davis
Heather Davis
Approval Engineer
  +1 (281) 396-1710

For registration questions, please contact the following:
Cynthia Ervin - 63 px
Cynthia Ervin
Regional Marketing & Academy Support Manager
(281) 396-1720


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