Hi All,

I've searched the forum and I've found that several people have asked this question but never got a resolution.

My question is how to input both the seismic loads and snow loads into CAESAR II.

I'm accustomed to input my seismic loads as Gx in vector 1, Gy in vector 2 and Gz in vector 3 as it makes the load case creation and segregation much easier (typical scenario)

But if we now want to add snow load, I don't see a logical way of doing so. I'm aware that I can input all of my seismic loads (Gx, Gy, Gz) in vector 1 and then add my -Fy for snow in vector 2, but then how do I create/segregate my load cases?? If I understand it correctly, in the latter scenario my vector 1 would be a resultant vector of all seismic loads acting in X, Y, Z. If that understanding is not correct then how do I create the load cases? (meaning my +U1 to OPE or SUS or -U1...)

Thank you in advance for your help

If you really want to use a g load to model snow, specify 1G for your Y (vertical) load and then include a multiplier in your load case definition. For example, if I want a .3 G load to simulate snow and 0.2 G to represent the vertical seismic component, I would use:
...+0.3U2+... for the snow case (U2 represents vertical) and
...+0.2U2+... for the seismic case

Dave,

I don't HAVE to use a G load for snow, I just thought it would be the cleanest approach. My specified snow load is 9 lbs per foot so 9/12 or -0.75 for the uniform load input. But if I'm going to do as you suggest (which a like the suggestion) then what is "G" in order to get the required 9 lbs? is it 0.75U2? That doesn't seem right.

The help menu says the following:"Your entries of X = 0.0, Y = -1.0, Z = 0.0 represent a 1.0g load in the minus Y direction, and is exactly equal to the pipe weight load in Y-up coordinate system"..."exactly equal to the pipe weight load" which seems that I would somehow need to add 9 lbs per foot to the load case?

I think I'm more confuse now...

I would not use G-loads for snow. You have the ability in CAESAR II to mix seismic in Gs with snow load in lb/in. Typically, I would use U1 and U2 for the horizontal seismic g-loads and U3 for your snow load (U3 = -0.75 lb/in). The only problem is if you also have a vertical seismic component. In that case, you may have to add the vertical component into your U1 and U2 vectors and consider the vector addition of vertical and horizontal components in your seismic portion of the evaluation.

Loren Brown
Intergraph

Thank you Loren

how do "consider the vector addition of vertical and horizontal components in your seismic portion of the evaluation"...that has been the problem from the start. How do I do that in CAESAR load cases? or otherwise.

The problem is that I do have a vertical seismic load but it's very small (0.039 in G's) and could easily be negligible (same for horizontal...0.089 in G's) but I feel obligated to include them since I don't have a good reason to "disregard" them. I know that a lot of time the vertical component of seismic is not included but I've never heard a good reason as to why...if anyone has a "standard practice" reason I would love to hear it please.

We're crossing messages. I am responding to the questions directed to me.
Uniform load in CAESAR II is pure load per unit length or acceleration in g. If you have a snow load given in load per unit length, then use it but remember that this linear load will change with pipe size and insulation thickness.
If you wish to use g load, then you will be responsible for defining that g multiplier. For example, if the total load per foot of pipe is 36 lbf/ft (that's pipe, insulation, refractory and fluid weight) and you want a 9 lbf/ft snow load, specify 0.25 g as your snow load in g (9/36).

You also have a conversation, here, with Loren. You question the difference between:
1) U1=X load & U2=Y load with a load case containing ...+U1+U2+...
2) U1=X and Y loads together with a load case containing ...+U1+...

These results will be the same. CAESAR II runs a single load vector - with all its components. So if you have a g load in X and Y you can parse it however you wish.

Thank you Dave, that clears up both questions. I should be good now.

Hi,

I have a similar problem, but with a uniform load due a metalurgical dust, my project criteria state that the load could reach up to 5% of accumulation inside the ducts. Can I put this load as Cladding (calculating the density and and thikness of this dust)?

The result will be accurate?

As a suggestion, could you include more vectors U (U1, U2, U3, U5, U5, etc) in order to make easier those kind of loads?

Thanks and best regards

related to the vertical g load, instead to use U vector it may be possible to use weight multiplier (e.g. instead +0.2 g U2, use 1.2W or for -0.2 g use 0.8W) in the load cases that involve the vertical g load. In this way one U vector become available for distributed load.

Regards,

Hi, thansk for your answer.

If I use the U vector for Seismic and Uniform load from the metalurgical dust, how can I discriminate the efect due the extra weight (present all time) and the efect due a seismic acceleration?.