Author Topic: Expressing Fault Tree Analysis in BBN  (Read 278 times)

Offline uppglassmel

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Expressing Fault Tree Analysis in BBN
« on: April 06, 2018, 17:01:10 »
Hello,

I am interested in using BBN to modify probabilities that are being fed into a Fault Tree event node. Hence, I would like to also incorporate the Fault Tree Analysis as part of the BBN node.

I have seen some researchers (J.E. Vinnem et al "Risk Modelling of maintenance work on major process equipment on offshore petroleum installations") where they have configured Fault Tree gates in HUGIN by having inputs as "1" or "0" according to the states of the child node such they it resemble a AND-gate or OR-gate.

I have done the same, but my outcome node's results are only "1" or "0" because the values in the conditional probability tables(meant to describe the node as AND or OR gates) are propagated as the actual probabilities.

Do you have any advice what I can do ( my model is attached).

I mean to model C1 as a outcome node, with C2 (0.7 False, 0.3 True) and C3 (0.7 False, 0.3 True) as the input nodes. Based on C1 having the nature of an AND-gate, if I feed evidence that C2 and C3 is true, then I would like to see C1 being reflected as (0.3 X 0.3 = 0.09 that True will occur).

Thank you in advance, I hope I have been clear

Mel

Offline Anders L Madsen

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Re: Expressing Fault Tree Analysis in BBN
« Reply #1 on: April 07, 2018, 20:53:23 »
Hello,

If you want P(C1=true|P2=true,P3=true)=0.3*0.3=0.09, then you can achieve this using a "noisy-add" gate as demonstrated in the attached model. You set P2_input=true and P3_input=true to get the desire result.

Hope this helps.
HUGIN EXPERT A/S

Offline uppglassmel

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Re: Expressing Fault Tree Analysis in BBN
« Reply #2 on: April 10, 2018, 16:49:47 »
Hej Anders,

Thank you for showing me the 'noisy-add' gate, it worked for an OR-gate as well.

Attached it here in case someone else might be interested in it

Very appreciative of your time!

Mel