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#18939 - 06/28/08 02:46 AM How to consider Sea Transportation Load
faizol Offline
Member

Registered: 06/08/08
Posts: 33
Loc: Malaysia
Dear Members,

Specification from our client as below:
"Vessel and their support shall be designed to withstand module loadout forces. A horizontal force of 0.7 times the empty weight of the vessel, and a total vertical downward force is 1.3 times the empty weight.The horizontal & vertical force and wind are to be assumed to act simultaneously through the center of gravity of the vessel"

So, anyone explain to me hoe to consider this specification as transportation load or factor above (0.7 & 1.3)to be consider at Seismic load(g loading)?
_________________________
[MUHAMAD FAIZOL]
faizol@mset.com.my

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#18981 - 06/30/08 08:11 AM Re: How to consider Sea Transportation Load [Re: faizol]
Mandeep Singh Offline

Member

Registered: 12/15/99
Posts: 600
Loc: Houston, Tx, USA
Dear Faizol,

You can input this as g-loading under Seismic codes tab. In the PV Elite notation x, z are the two horizontal directions and the y is the vertical direction. You should also two gy cases, one with +ve gy and other with -ve gy.

Are these transportation only loads or they are present during the operation of the vessel?

For example, if this vessel is located on an off shore platform, then the wave loading (specified using g-loading) and wind loading acts simultaneously. In that case you have to specify in the program to combine wind and seismic loads, instead of the typical option of taking the maximum value.

_________________________
Best Regards,
Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM

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#19088 - 07/06/08 02:39 AM Re: How to consider Sea Transportation Load [Re: Mandeep Singh]
faizol Offline
Member

Registered: 06/08/08
Posts: 33
Loc: Malaysia
Dear Mandeep,

Sir, when i applied 0.7 as horizontal force (Gx & Gy) & 1.3 as vertical vessel to g-load under seismic codes tabes, then during analyze result shown crital error and warning which is unity check at saddle exceed 1.0.and baseplate thickness become higher.

Attached below error output for your kind perusal.

Please advise us how to solve this problem and your prompt respond are appreciated.

Thank you.


Attachments
356-G-load.pdf (1430 downloads)

_________________________
[MUHAMAD FAIZOL]
faizol@mset.com.my

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#19091 - 07/06/08 12:15 PM Re: How to consider Sea Transportation Load [Re: faizol]
Mandeep Singh Offline

Member

Registered: 12/15/99
Posts: 600
Loc: Houston, Tx, USA
Faizol,

Well, it is indicating that you need to re-design your saddle and its support structure. So, it is adequate.

There are some engineering handbooks that have some standard saddle dimensions. You can check it.

In PV Elite we have provided standard saddle dimensions from the Dennis Moss book. On the saddle dialog, you can choose the Select saddle option.

You should also check the calculation of the saddle Q load.
_________________________
Best Regards,
Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM

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#19092 - 07/06/08 07:08 PM Re: How to consider Sea Transportation Load [Re: Mandeep Singh]
faizol Offline
Member

Registered: 06/08/08
Posts: 33
Loc: Malaysia
Dear Mandeep,

Sir, than you for your advice, i already try to change the saddle width, baseplate width, but result still same. Could you guide me what parameter will be reduce the Unity value.

your cooperation will highly appreciated.

Thank you.
_________________________
[MUHAMAD FAIZOL]
faizol@mset.com.my

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#24970 - 02/19/09 07:35 AM Re: How to consider Sea Transportation Load [Re: faizol]
SK Tan Offline
Member

Registered: 01/15/09
Posts: 66
Loc: Malaysia
Dear Mandeep,

Interest with your statement :

In that case you have to specify in the program to combine wind and seismic loads, instead of the typical option of taking the maximum value.

Please advise how to get this combine wind/seismic done.

Thanks!

S K Tan

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#24984 - 02/19/09 10:55 AM Re: How to consider Sea Transportation Load [Re: SK Tan]
Mukesh Offline
Member

Registered: 11/12/06
Posts: 125
Loc: Ahmedabad, Gujarat, India
SK Tan,

In Load Cases-> Installation / Misc Options -> Saddle Calc Option Submenu-> Combine wind & earth loads check box is there.

Mukesh

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#25006 - 02/19/09 07:44 PM Re: How to consider Sea Transportation Load [Re: Mukesh]
SK Tan Offline
Member

Registered: 01/15/09
Posts: 66
Loc: Malaysia
Hello, Mukesh.

Thanks for your hint.

Yes, found it. This will save some productivity on our engineer team.

Appreciate for your sharing.

S K Tan

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#25274 - 02/27/09 01:03 AM Re: How to consider Sea Transportation Load [Re: SK Tan]
Mazaffar Hussain Offline
Member

Registered: 05/06/08
Posts: 11
Loc: New Plymouth, New Zealand
A very informative discussion. Thanks to all.

I’ll highly appreciate if anybody could tell me what other design factors should be considered (different to onshore) while designing offshore equipments. Please refer any literature regarding this.


Edited by Mazaffar Hussain (02/27/09 01:05 AM)
_________________________
Mazaffar Hussain
Senior Static Equipment Engineer
Shell Todd Oil Services Ltd
167 Devon St West, New Plymouth, New Zealand

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#25300 - 02/27/09 10:08 AM Re: How to consider Sea Transportation Load [Re: Mazaffar Hussain]
Mandeep Singh Offline

Member

Registered: 12/15/99
Posts: 600
Loc: Houston, Tx, USA

This is more of a question than an answer...

As there would be constant movement on platform, would you pay more attention to support welds. For example would you grind the welds smooth to reduce stress concentration.

what about corrosion allowance (external)

any thing else ?
_________________________
Best Regards,
Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM

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#36519 - 06/30/10 06:46 AM Re: How to consider Sea Transportation Load [Re: faizol]
kodzak81 Offline
Member

Registered: 05/19/10
Posts: 28
Loc: Europe
Is this thread still available?

I'm interesting in the following. What are those Gx, Gy and Gz accelerations under G Loading in pvelite? Is that G force? I'm asking because I have been given accelerations in m/s2 by client... And as I can see the G factors in pvelite are non dimensional. So I assume it is G force which is obtain as G=a/g

where,

a - given acceleration
g = 9.81m/s2

Is this correct?

Thanks in advance.


Edited by kodzak81 (06/30/10 06:50 AM)

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#36575 - 07/02/10 02:07 AM Re: How to consider Sea Transportation Load [Re: kodzak81]
SK Tan Offline
Member

Registered: 01/15/09
Posts: 66
Loc: Malaysia
Hi kodzak81,

Yes, you are right.

To Moderator,

PV Elite can compute support under both wind and seismic load simultaneously, on saddle, legs and lugs.

Any reason left out skirt? Will this be added in coming build?

Thanks!

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#36796 - 07/12/10 12:00 AM Re: How to consider Sea Transportation Load [Re: SK Tan]
SK Tan Offline
Member

Registered: 01/15/09
Posts: 66
Loc: Malaysia
Any reply from Moderators?

Vertical vessels with skirt installed on FPSO are exposed to wind and g-loadings simultaneously, thus the combine-load shall be analysed.

Thank you!


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#36831 - 07/13/10 03:54 AM Re: How to consider Sea Transportation Load [Re: SK Tan]
kodzak81 Offline
Member

Registered: 05/19/10
Posts: 28
Loc: Europe
Originally Posted By: SK Tan
Any reply from Moderators?

Vertical vessels with skirt installed on FPSO are exposed to wind and g-loadings simultaneously, thus the combine-load shall be analysed.

Thank you!



Yes, is there anyone who can reply to this? I'm also curious about this issue.

Cheers.

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#36927 - 07/19/10 02:36 AM Re: How to consider Sea Transportation Load [Re: kodzak81]
kodzak81 Offline
Member

Registered: 05/19/10
Posts: 28
Loc: Europe
I can't believe that there is nobody to say something on this issue. "It is not possible" would be enough. I just want to know is it possible or not.

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#37333 - 08/09/10 09:02 PM Re: How to consider Sea Transportation Load [Re: kodzak81]
SK Tan Offline
Member

Registered: 01/15/09
Posts: 66
Loc: Malaysia
Dear Mandeep and/or Scott,

Hi, can help to reply question about combining both wind & seismic (g-loadings) for skirt equipments?

Nowadays, we have many design jobs for FPSO project, really need to know how soon can PV Elite can implement it to suit industrial/clients' need.

Regards!

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#37681 - 08/26/10 03:24 AM Re: How to consider Sea Transportation Load [Re: kodzak81]
SK Tan Offline
Member

Registered: 01/15/09
Posts: 66
Loc: Malaysia
Dear Mandeep,

About 2 months, can help to reply when PV Elite will combine both wind and seismic loads on skirt support equipments?

We did not see this feature on August built yet. Still restricted to Saddle, leg and lug only.

Or there is any difficulty for PV Elite to do so?

Thank you!


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#37697 - 08/26/10 05:29 PM Re: How to consider Sea Transportation Load [Re: SK Tan]
Mandeep Singh Offline

Member

Registered: 12/15/99
Posts: 600
Loc: Houston, Tx, USA
Dear Friends,

Just a reminder that the discussion forum should not be considered a support tool. It is tool for discussions among engineers. Sometimes we get so busy that we cannot come and participate in the discussions even if we want to.

I will recommend that you send an email to the tech support in the future if you need immediate attention.

But, we should have replied sooner, specially this feature is already present in PV Elite.

Now, to answer your question, yes it is possible to do to so. In one of my previous posts I should how to combine wind and seismic for a horizontal vessel and vessel on legs or Lugs.

Here is the procedure to combine Wind and seismic for a vertical vessel on a skirt support.

Go to Load Cases tab.

Press the Button "Set Load Cases to show WI and EQ Scalars" so that any wind/seismic multipliers are shown in the load case description.

Now, check the box "Use and Allow Editing of Local Scalars in the load cases"

Now, you are ready to play with the load cases. There are descriptions for each loading condition which can be accessed from the help system. For example,

IP - Internal Pressure
WI - Wind load
EQ - Earthquake loads

...

You will see that the load cases by default have just wind or earthquake and not both. Typically this scenario, the worst earthquake (per your design) will rarely strike when the worst hurricane is coming. If that happens then God save us….

Now, if you have a vessel located on a floating platform or on a ship and you will model the wave motion probably as g-loading (from the seismic tab) and then you would want to combine wind and “seismic” to get a typical operating case.

Another situation where this is useful is that some specifications call for combining some percentage of wind with seismic or vice-versa.
Now, let’s see how we can edit a load case to combine the effect of wind/seismic.

For example, default load case 7 can be modified from

IP+OW+WI+FW+BW

to

IP+OW+WI+EQ+FW+BW

pay attention to the any applied forces and make sure that they are included in both wind or seismic condition. There is a limit on number of characters in the load case description. So, pay attention to the Load Case output report.

Now, you are ready to analyze your job. Setting the load cases will cause the longitudinal stress in the elements to be computed based on the load cases that you have set up.

Next the question is how to design the supports for this combined wind/seismic loading, as this for a skirt supported vessel, go to the Basering dialog and check the box “Determine the basering design bolt load accounting for the Load Case Factors”. This will actually get the bolt design load on the tensile side (windward) of the vessel and concrete design load from the compressive side (leeward).

Now you are done. Review the results to make sure that you understand the answers.
_________________________
Best Regards,
Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM

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