Does anyone know how to compute the structural factor (CsCd) for wind loads on pipe per EN 1991-1-4? The help document in Caesar II says it's in Annex D but I don't see anything for pipe. I see chimneys, maybe they are thinking you could use that for pipe. I'll just use CsCd = 1, if I can't find anything but I am curious to know. I'm in the US and this is my first foray into the Eurocode.
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Structural Factor CsCd on Pipes per EN 1991-1-4
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Cd is usually a notation reserved to mean a wind drag coefficient.
Wind direction Z=1 others = 0, I would suspect means wind is directly perpendicular to pipe.
I don't have the code, or the Caesar user maual.
What does EN-1991 say about those variables?
What does Caesar say about those variables?
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Wind direction Z=1 others = 0, I would suspect means wind is directly perpendicular to pipe.
I don't have the code, or the Caesar user maual.
What does EN-1991 say about those variables?
What does Caesar say about those variables?
Reaction to change doesn't stop it
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BigInch, Cf is the wind drag coefficient. It's also in the equation that I show in my screenshot. CsCd is what they call the structural factor. It takes into account the effect on wind actions from the non-simultaneous occurrence of peak wind pressures on the surface (Cs) together with the effect of the vibrations of the structure due to turbulence (Cd). Whew, that's clear enough, right?
The code then goes on to give some cases where you can take CsCd as 1. The closest thing to pipe is a chimney with a circular cross-section whose height it less than 60 m and 6.5 times the diameter. But that's a cantilevered "pipe" so I'm not sure you can use that to justify using a value of 1.
Next the code talks about the detailed procedure for calculating CsCD, but all the cases show members with a rectangular cross-section. That leaves Annexes B, C, and D. Like I said in my OP, CAESAR help says to use Annex D but I'm not seeing how that applies to pipe.
What does CAESAR say about those variables? Not much. Here it is:
"Structural Factor [CsCd] - Structural factor used to determine the force on the vessel. This value is defined in Section of the EN 1991-1-4:2005(E) Wind load specification in Annex D. This value normally ranges between 0.90 and 1.10. The greater the structural factor value, the higher the element load."
Notice after the word "Section" there is no section number. I think they meant to put one, or they just used bad grammar. Also, why do they refer to a vessel? Isn't this for pipe also? Instead of "help" this should be called "no help".
I thought this being a worldwide forum there would be lots of people that have already figured this out. I'm guessing the reality is that people just plug in 1.0 or maybe 1.1 to be safe and move on.
The code then goes on to give some cases where you can take CsCd as 1. The closest thing to pipe is a chimney with a circular cross-section whose height it less than 60 m and 6.5 times the diameter. But that's a cantilevered "pipe" so I'm not sure you can use that to justify using a value of 1.
Next the code talks about the detailed procedure for calculating CsCD, but all the cases show members with a rectangular cross-section. That leaves Annexes B, C, and D. Like I said in my OP, CAESAR help says to use Annex D but I'm not seeing how that applies to pipe.
What does CAESAR say about those variables? Not much. Here it is:
"Structural Factor [CsCd] - Structural factor used to determine the force on the vessel. This value is defined in Section of the EN 1991-1-4:2005(E) Wind load specification in Annex D. This value normally ranges between 0.90 and 1.10. The greater the structural factor value, the higher the element load."
Notice after the word "Section" there is no section number. I think they meant to put one, or they just used bad grammar. Also, why do they refer to a vessel? Isn't this for pipe also? Instead of "help" this should be called "no help".
I thought this being a worldwide forum there would be lots of people that have already figured this out. I'm guessing the reality is that people just plug in 1.0 or maybe 1.1 to be safe and move on.
Sorry, thought I might be able to help, but EN-1991 isn't used at all in the US and I have not used it anywhere myself. It seems to be modeling a dynamic response. Too bad it doesn't give enough detail to make it actualy useful. ASME and DNV are far more common.
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Chicopee, but it doesn't. When I was describing in my last post about how the code gives some cases where you can take CsCd as 1.0, that was from section 6. It seems to me that EN 1991-1-4 was written without a single thought of pipe. OK, I get that people writing a code primarily for buildings could forget about pipe that zigzags all over a process plant, but at the end of the day designers have to use something. If that something is just use CsCd=1 and move on, that's fine. I guess I would have thought there would be people from Europe who are familiar with this and could tell what the practice is.
Ha! Got me. I actually thought EN 1991 was an obscure pipe design code, because you said it was a Caesar option. Nobody I know uses structural design codes as a pipe design criteria. Maybe they do that in nuclear pipe design or something. Who told you to use EN 1991 for your pipe design and what piping code are you using?
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You must not know many people then.![[bigsmile]](/data/assets/smilies/bigsmile.gif "[bigsmile] [bigsmile]")
Here's an excerpt from ASME B31.3-2016
301.5.2 Wind. The effect of wind loading shall be taken into account in the design of exposed piping. The analysis considerations and loads may be as described in ASCE 7.
ASCE 7 is model building code. Not a pipe code per se. Just to be clear, I understand you don't do the actual design of pipes using structural codes but you do use structural codes to determine the wind and seismic loads on pipe.
As far as who told me, we were asked to help out a sister company in Europe who was overloaded (we're in the US) on a job in Norway. We were given very little info, so I started hunting around and from what I could find out it seemed we should follow the Eurocodes. I opened up CAESAR II to see what codes it supported for wind and the only European code it had was EN 1991-1-4. I should stop at this point and rub it in some more. It also listed ASCE 7, IBC, NBC, and UBC, all "structural codes". Anyway, I asked my counterparts if this was the right code to use and if so could they supply the wind speed, terrain category, etc. They supplied the relevant input except for the structural factor (CsCd), thus that brings us to where we are today.
Chicopee, I got very close to the same value as CAESAR II when I plugged in CsCd=1 and used the same in a hand calculation. Not sure what that proves other than I agree with CAESAR's number. Still doesn't tell me what CsCd should be.
Here's an excerpt from ASME B31.3-2016301.5.2 Wind. The effect of wind loading shall be taken into account in the design of exposed piping. The analysis considerations and loads may be as described in ASCE 7.
ASCE 7 is model building code. Not a pipe code per se. Just to be clear, I understand you don't do the actual design of pipes using structural codes but you do use structural codes to determine the wind and seismic loads on pipe.
As far as who told me, we were asked to help out a sister company in Europe who was overloaded (we're in the US) on a job in Norway. We were given very little info, so I started hunting around and from what I could find out it seemed we should follow the Eurocodes. I opened up CAESAR II to see what codes it supported for wind and the only European code it had was EN 1991-1-4. I should stop at this point and rub it in some more. It also listed ASCE 7, IBC, NBC, and UBC, all "structural codes". Anyway, I asked my counterparts if this was the right code to use and if so could they supply the wind speed, terrain category, etc. They supplied the relevant input except for the structural factor (CsCd), thus that brings us to where we are today.
Chicopee, I got very close to the same value as CAESAR II when I plugged in CsCd=1 and used the same in a hand calculation. Not sure what that proves other than I agree with CAESAR's number. Still doesn't tell me what CsCd should be.
Going conservative with 1.1 and done may be an easy out. I have found the following PowerPoint presentation that goes into detail on CsCd calculation that may be of help to you.
The analysis considerations and loads may be as described in ASCE 7. May = optional.
You can also use any wind load calculation method you deem is sufficient for your design.
[highlight #204A87]ASCE 7 ?[/highlight] What do you do when it is an offshore pipeline riser below water level, or an undersea pipeline exposed to currents. Check another box in Caesar?
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You can also use any wind load calculation method you deem is sufficient for your design.
[highlight #204A87]ASCE 7 ?[/highlight] What do you do when it is an offshore pipeline riser below water level, or an undersea pipeline exposed to currents. Check another box in Caesar?
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BigInch, I understand that "may" means. All I'm telling you is in my experience ASCE 7 is what is almost always used in the U.S. to determine the wind loads on pipe, at least in petrochem plants. Granted, it is an imperfect document for pipe. As such, ASCE wrote a report entitled "Wind Loads and Anchor Bolt Design for Petrochemical Facilities". It's purpose is to bring about a more uniform application of practices across the petrochemical energy industry. It uses ASCE 7 as the basis. It looks like this has been republished as "Wind Loads for Petrochemical and Other Industrial Facilities" but I don't have that particular publication.
I'm curious, if you design pipe sans building code, how do you arrive at a wind speed?
Regarding your wise a$$ question about using Caesar, I was merely using Caesar to get an idea of what codes are popular for wind load determination. I'm not a pipe stress engineer, and I don't have one here in house at the moment to ask, so I was using any means at my disposal to find out. Caesar has a long reputation a being the preeminent pipe stress software, (not saying I agree or disagree, just what I hear) so I figured it would point me in the right direction for a viable wind code.
I'm curious, if you design pipe sans building code, how do you arrive at a wind speed?
Regarding your wise a$$ question about using Caesar, I was merely using Caesar to get an idea of what codes are popular for wind load determination. I'm not a pipe stress engineer, and I don't have one here in house at the moment to ask, so I was using any means at my disposal to find out. Caesar has a long reputation a being the preeminent pipe stress software, (not saying I agree or disagree, just what I hear) so I figured it would point me in the right direction for a viable wind code.
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