Imposed Displacement for uneven seabed (Inclination)

Good day to you Afiif, 

I need to fully understand your modeling approach. 

1. Mudmat is installed flush with the seabed floor, or the mudmat is not installed flushed with the seabed floor

Modeling Approach - Need to create 2 models that has the correct piping layout 

or 

2. Mudmat is installed flush with the seabed floor and then under some circumstances moves to a new location

Modeling Approach - Model center-line of pipe as installed, Model Mudmat as multiple nodes with v-stop supports (gap down = 0, gap up = 100) as you have already done above. Again, as you know, using Insert Support Displacement command assign it to a load case with the correct amount of displacement per that load case. 

Recall from AutoPIPE help, Impose support displacement is applied to the base of the support. If the support stiffness is Rigid, than 100% of the displacement will be transmitted to the piping. Otherwise, as the support stiffness changes, so does the amount of displacement transmitted to the piping. 

Regards,

Mike Dattilio
Bentley Systems Design Analyst
Design Engineering Analysis group
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Dear
Mr. Mike Dattilio

Thank you for your kindly reply.

1. Top of Mudmat is installed flush with the seabed floor (same elevation). However, I have to perform sensitivity analysis to make inclination of 2-5 deg due to uneven seabed (along the mudmat)

2. I've input the imposed data value as linear function from end to end point of mudmat. (Please see attached table above). As conversatism, v-stop support stiffness set as rigid to represent the mudmat rigidity. 

May your kindly advise for this.

Thanks and regards
Afiif

Good day Afiif, 

The most important piece of information is "make inclination of 2-5 deg due to uneven seabed (along the mudmat)". Thus meaning that the mudmat is not installed level and then moves during operating conditions. The Mudmat is installed at some angle. 

With that information, I would suggest not using Imposed support displacement, as it assumes that the pipe has already been installed and during operating load cases the pipe supports moves from the initial location. 

A good example when to use impose support displacement,  Nozzle connection to a vessel, where the vessel is modeled as an anchor. During operating conditions, the vessel physically grows in some direction(s). Thus the anchor (representing the vessel), needs to be displaced some distance to replicate the equipment movement. 

In your case, create a new model with the correct installed pipe routing and analyze the system. Again, suggest not to use Impose Support displacement in evaluating this scenario. 

 Regards,

Mike Dattilio
Bentley Systems Design Analyst
Design Engineering Analysis group
===================================================

Dear
Mr. Mike Dattilio

Thank you for your kindly advise. Regarding to your reply, I agree with your advice. In this case, the support (mudmat) is an actual route for the pipe and already been installed during operational case. It is mean that I have to sketch pipeline drawing in autocad to represent the natural bend, instead of using imposed displacement. I draw the conclusion that imposed displacements are more represent as load. Thank you for your advice sir, it is helpful for us.

Thanks and regards