Combining Building Codes: Is it necessary or even possible/rational? 2

[jochav5280]

Dear All:

I am working on a project where our client is using ASCE 7-10 as the governing building code for a site in the Peruvian mountains.

Would someone advise if this is okay, or if we need to use the building code associated with where the project is actually located, (i.e. Peruvian building code?) Our office has attempted to adjust our load combinations to cover the combinations called for in Peru as well as adjust our seismic load effects to at least meet theirs, however, I don't think this is the correct approach since the (2) codes are clearly not compatible. For instance, a Steel Ordinary Concentrically Braced Frame per ASCE 7-10 requires a R-Factor of 1.5, while the Peruvian code would require an R-Value of 6. Both codes calculate the lateral and vertical seismic load effects with different equations, so it doesn't make sense to me to try to adjust ASCE 7-10 requirements to meet the Peruvian code. In our case, we choose to utilize structural systems for our structures with lower R-values, which yields higher seismic loads, which allows us to design per the regular AISC 360-10 detailing requirements as opposed to having to consider the ductile AISC 341-10 detailing requirements. The relatively high Peruvian R-values imply to me that they too are based on a more ductile design similar to AISC 341-10; therefore, we are designing our structures to remain theoretically elastic, while it appears the Peruvian code designs them to be relatively more ductile to dissipate seismic energy. In short, I'm concerned that our attempt to compare apples to apples is actually producing apples and oranges and producing overly conservative/expensive structures. Is it not possible to just design per ASCE 7-10 as we've received the ASCE 7-10 seismic design parameters for the region from the client. Are there any liability issues if our client gave us approval to design per ASCE 7-10 only?

I'd greatly appreciate help understanding the correct approach; many thanks in advance!

Best regards,

jochav5280

 

[KootK]

I feel as though it is the local building department that should decide the governing code rather than your client. From an ethical perspective, I think that you're duty bound to either design to the locally accepted code or at least notify the local building department of the situation.

Once upon a time I wanted to design an extended shear tab connection. Unfortunately, there's no such thing in the Canadian steel code. I called CISC and asked what they thought of my using the AISC provisions. They told me to go ahead but directed me to use all of the AISC provisions rather than proceedings buffet style. Apples and oranges, just like you said.

If you go all ASCE, I'm no sure how you'll get your hands on statistically compatible environmental data.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Brad805]

Koot, thanks for mentioning the AISC conversation.

 

[jfmann]

As for liability issues.......that is quite a swamp these days.........since not only must you satisfy laws of Peru (which may be even more "fluid" that US laws), but cases seem to cross national boundaries quite easily. Better have good legal backup........and consult with them now!

As for design approach........as first reaction, I see no big problem using one code primarily along with more conservative requirements of the other code as deemed appropriate. However, as you note, using one code is preferable if at all possible within legal constraints.

Most important though is whether any client has the legal right to simply waive the Peru code in favor of a more liberal code.......which I doubt. Even if they claim such right......get your legal team to be very sure, or do not accept such claim.

John F Mann, PE

http://www.structural101.com

 

[jochav5280]

Dear Kootk:

Thank you for your input!

The ethics are definitely a concern; some of my colleagues making these decisions are being reckless in my opinion and I see them just make judgments that they should really follow-up with to confirm that they are correct.

In looking at the Peruvian steel specification, their limit state equations all appear to be identical to AISC 360, so I'm not sure why they didn't just direct designers to follow AISC/ASCE as opposed to creating yet another set of codes to follow. There load combinations appear to be nearly identical as well, with ASCE being on the more conservative side.

Thanks again,

jochav5280

 

[jochav5280]

Dear jfmann:

Thank you for your input. I'll utilize my in-house South American collegues to help get asnwers from the Peruvian building authority.

Overall, I'm hearing what I was expecting; it's irresponsible and possibly illegal to just make the assumption that the client's approval to use an alternate building code is okay.

Thanks again,

jochav5280

 

[KootK]

It's hard to imagine that the ethics will be a serious issue here. Surely the owner will want to do the right thing regarding the code as the liability associated with doing otherwise would be enormous.

In the steel connection situation that I mentioned, I actually went a little bit rogue. I used AISC provisions for the capacity checks but Canadian codes for the loads. I see this as being more rational and one of the benefits of LRFD design: loads and resistances are separated from a reliability and statistical standpoint. That concept is admittedly a little murkier with seismic however.

Were I to employ this same method to your situation, I think that it would be rational to do this:

1) Calculate elastic level seismic loads using the ASCE.
2) Modify the seismic loads using Peruvian R-Values.
3) Design your members using the Peruvian steel code.

Or vice versa. As you intimated, I feel that it is important for the force reduction factor to be consistent with the ductility expectations embodied in the material design specification. Still, my preference would be to not mix codes if possible.

@Brad: I did some work with a glass specialist who claimed that, because of NAFTA, he could use any North American code in any North American jurisdiction. And he actually did this on numerous occasions for some pretty high profile work, seemingly without repercussion. I never got around to verifying that this was legit. He also claimed that he didn’t actually have to follow any code, he just had to be able to defend himself in court. Glass guys: mavericks by nature, clearly. Or at least translucently.


I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jochav5280]

Thank you KootK:

I appreciate your response and we are in agreement.

Best regards,

jochav5280

 

[Brad805]

This is an interesting discussion. Canadians and other less populated countries do as well. The reality of the internet is many people do not want to pay for information so many of governing bodies are limited. In the US you have large associations like the ASCE, ACI, and the AISC that are very aggressive at marketing. While it can be annoying to be constantly bombarded with new literature to buy the upside is that is the reason they can continue to research and produce more data for us. We do have the same associations in Canada, but they are small and simply do not have the funding to do as much as their US counterparts.

Koot, your comment about extended shear tabs was very timely. I was reviewing a paper on the weekend for a project on extended shear tabs that cited the US code. The load factor decision is the primary problem I have had in the past.

 

[sponton]

I always thought that at the end of the day engineering judgement prevailed in cases where code really isn't applicable/compatible or methods approved by code aren't really clear on the topic. I mean at the end of the day you cannot set the whole range of cases engineering project runs into in a single code/method. So if the design works applying rational analysis, anything should be allowed, assuming this is on the safe side of course.

 

[KootK]

I pretty much agree Sponton. If my jurisdiction has a code provision, I use it. If it doesn't, I'll turn to external codes. Failing that, I'll start making stuff up.

One upon another time I first principle designed a lifting lug before I knew that there were standards for such things. I was out by a factor of two with no math errors. I revel in the fact that most of what I do has been done before. Precedent is a big part or structural engineering.[pre][/pre]

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.