Hello everyone,

I am new to this business so please bear with me. I am doing modeling of trap skid piping which is going to be on topside. I have following confusions . questions:

1. When I select B31.3 and occ load case, do I have to define the occ load factor or the software will take care of it automatically knowing the factor from the code.

2. Per B31.3 no wind loads shall be considered with the seismic, since the offshore does not have the seismic but have deck motions, should I combine g-loads with the wind or treat them separately.

3. I have been given blast overpressure (1.5barg) and blast wind pressure (.3barg), I assume that I can combine them by converting Pdyn (.3 barg) to static pressure i.e. Pdyn x Cd x DAF = 0.3 x 1.2 x 1.5 = 0.54 barg and add it to the overpressure of 1.5 barg. Then, the total pressure for user defined wind profile will be 2.04 barg.

4. For the user defined wind profile (pressure vs elevation), why does the software asks for shape factor and even when I select user defined pressure vs elevation the right hand side of the wind load case window still asks some parameters based on ASCE-07, why?

5. For NMD-22 27 degrees tilt, should I combine this with the blast loading also? The specs says that no environmental loads (i.e. wind) shall be combined with blast or NMD-22, however, I am not sure if I should combine these two together since both of them are worst case scenarios and may generate very high loads.

6. I have to apply wind from all directions and have to evaluate wind for 200 year, 10,000 year, 17 degrees tilt with 5 year wind, and 10 year wind with tow accelerations. As you can see I have four different wind cases and Caesar-II have only four wind input options. How can I apply wind from the transverse direction of skid.

I believe I have asked too many questions and I will stop here. I will probably ask more later:)

Any help on any of the above questions will be highly appreciated.

Thanks a lot.

1) The Codes allow different occasional factors based on the duration and frequency of the load. Yes there is a default, but I wouldn't rely on this, it may not be correct for your particular situation.

6) Use direction cosines to apply the wind in non-orthogonal directions.

2-5) You should discuss these questions with your project lead.

Thanks Richard,

Can you please help me out on no. 4 above.

4. For the user defined wind profile (pressure vs elevation), why does the software asks for shape factor and even when I select user defined pressure vs elevation the right hand side of the wind load case window still asks some parameters based on ASCE-07, why?

I assume that the shape factor is to convert velocity to pressure and most of the time its value is 0.65 for cylindrical shapes. However, if I have already converted my values to pressure why do I have to define it in the software? I might be missing here something and just wanted to confirm with you.

Thanks again.