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Thursday, August 20, 2009

Continue of Part 9 - On Bottom Stability Analysis


On Bottom Stability Using AGA


























Level 1


-Its calculate the static stability


-Airy waves theory and Morison force apply


- A cohesive soil retains its restraining force


Level 2


-Calculates value of design wave height spectral density function

-The peak frequency of the bottom velocity spectrum is determined

-Maximum and minimum in-line hydrodynamic forces for the largest 200 waves contained in an assumed 4-hours long build-up sea state are calculated.


-Maximum and minimum in-line forces for the largest 50 waves during a subsequent 3hours long design sea stated are as in step above.


-Hydrodynamic forces for a complete cycle are calculated for four level of bottom velocity which are expected in a 3hours long design sea state.


-The four bottom velocities are :


  • U1/3 = 1.0Us
  • U1/10 = 1.27Us
  • U1/100 = 1.66Us
  • U1/1000 = 1.86Us

Output example from my project before :



6 comments:

Hadi said...

Salam Bro,
Can you explain more detail on soil description?
For example in AGA input....
i just new in it..

asri bin rafie said...

Hi hadi,
When we talk about On bottom stability of pipeline, either AGA or DnV, soil is major factor to make sure pipeline stable on seabed or not other than wave, current velocity, and phase angle.

Soil description and characteristic will be divided into two test which are classification and engineering test.

Classification test is referred to know what type of soil, which are clay, silt or sand.

Engineering test is referred to strength of soil which is sand (soil angle), clay (Su) and silt (which have both Su and angle). These result will be used as a input to run the On bottom stability analysis.

First thing first, you need to understand on how to collect the correct soil data so that your result will be a realistic without no problem comes later.

OGA PIPELINE
THE BEST PLACE TO START

Hani nurul said...

salam Asri,
I just discovered your blog. Really interesting. Can you post more detail about using AGA level-3, when AGA level-3 use, and input consideration....
for level-2, how to takeout the result...i just got trained AGA last month...sorry for any inconvinience

asri bin rafie said...

Hi Hani Nurul,
Thanks for visiting my blog.

I'm promise soon I'll post more details about AGA level 3. For first basic understanding, AGA level 3 more concentrated on Dynamic analysis, which is you must understand the wave response and others related to that.

For level 2, on the output AGA, please look at note no. 3 which is explain on how to pick up the result from AGA.

Let join the OGA PIPELINE community for more info.

OGA PIPELINE
THE BEST PLACE TO START

Hani Nurul said...

hai Asri..
thanks for the feedback...
and this blog really open my point of view in pipeline especially for graduate engineer...
thanks again..will wait your next post

asri bin rafie said...

Hi Hani,
For more information about the OGA PIPELINE blog, please join our blog community.

OGA PIPELINE
BEST PLACE TO START