Explaining wind and seismic to nonstructural engrs 1

[dozer]

Does anyone know of a good article that explains how to properly specify wind and seismic loads to essentially a layperson?

Everytime I start a new project I go on this rant. Here's an excerpt from the spec I'm currently looking at.

Structural Design Basic Wind Speed (V): 30 m/s

That's it, nothing else on wind. No building code specified. No hint if this a 3 second gust or what, no nothing. Seismic is just as bad.

I should mention I work in the oil and gas process plant world. Anyway, I've tried to explain to our salesman over and over again what we need but they just don't get it. Maybe if I can hand them an article that explains this stuff on their level they will start asking our clients for this info up front.

 

[jike]

Why don't you just create a document that he can use with all the variables that are required for the particular site. For instance:

Basic Wind Speed = xx mph
Exposure
Importance
etc.

Ss = xx S1 = xx
Site Class xx
Seismic Use Group = xx
Seismic Design Catagory = xx
etc.

 

[msquared48]

If fulfilling their sales depend on your work, then tell them that THEIR job can't be started, let alone completed, until the information on the form is completed.

If their comissions are placed in jeopardy, then the information you need will suddenly become far more important.

Mike McCann
MMC Engineering

 

[MiketheEngineer]

Agree w/ Jike but you might add some definitions - like for exposure - just what is A, B, C or D

 

[Hanif08]

For a layman pictures are better than words. Try googling and chose something with pictures.

Here is one suggestion for wind:

http://umsis.miami.edu/~lpittack/cae614proj.html

 

[mrpid]

I do not know what the governing building code would be in your area. But if you look in the IBC, Section 1603 gives specific requirements as to what should be on the construction documents. I would imagine other building codes would have similar rqmts.

 

[UcfSE]

I don't think laypeople should be specifying these parameters. How likely is a client to know what S_s to use and whether it is correct? They might think wind speed is category 3 hurricane, which is no good to us.

I would try the approach of deciding what information you need that a client is likely to know that will help you determine what you need, and tell they salesperson to get that. They may not know the wind speed, but they should know the location, from which you should figure out the wind speed and seismic parameters, for instance.

 

[JStephen]

It sounds like this may be foreign work, in which case location doesn't help much if using the INTERNATIONAL Building Code.

 

[jike]

It would help if dozer would explain to us what exactly his role and others role are in his business. Is he a consultant or responsible for hiring consultants? Is he a manufacturer? National or international, etc.

This will helps us then give you better advice.

 

[swearingen]

Really, you just need to know where it is. The governing codes are based on your location. This is true for other countries as well. If they don't have one, offer an appropriate one and follow it.



If you "heard" it on the internet, it's guilty until proven innocent. - DCS

 

[dozer]

Jike, good suggestion I need to make a "cheat sheet" for each of the common building codes that outlines the information I need. I know I'm being unreasonable in expecting people to understand their job but I would like these guys to understand why a wind speed all by itself is not sufficient. I've tried explaining it for over twenty years and I'm tired of it. I was hoping to find an article that gave a succinct, easy to understand synopsis of why we structural engineers need this info so I could just hand it to people. I could write it myself but I don't want to reinvent the wheel if somebody has already done it.

What do I do? I do the structural analysis and design of various types of equipment, platforms, pipe racks, etc. in process plants (oil and gas). The way it usually works is a gas producer or someone like that will hire a consultant to design a plant or more often "shephard" the process. This guy will write specs that we will then use to design our portion of the plant. When I said laypeople, I just meant a layperson in the sense they are not a civil/structural engineer. Presumably they are an engineer thoguh. I surely don't expect an English major to be writing technical specs.

So anyway, these specs are multidiscipline in nature. Here's the part that kills me. If I told you the name of the company that wrote the latest spec that sent me to my soapbox you would very likely know it. They have literally thousands of engineers. Yet all they can muster for the wind load section of the spec is "Design wind speed: 30 m/s". Aaagh! If that isn't bad enough our people who review this crap before bidding never catch that that is not enough info, hence my desire to educate. Or rather, give them a tool to educate themselves because, did I mention, I'm tired of explaining it!

And yes, JStephen, this particular job is foreign (to the US). Which is doubly frustrating because I don't know the Russian SNiP code from a hole in the ground. But that's okay because evidently neither does the guy that wrote the specs.

I don't agree that we just need to know where it is. As I've stated we design projects all over the world. I would much rather you tell me what your wind exposure category is rather than me guessing because I've never seen (and probably will never see) the area. Same for soil type. I'm not Carnac the Magnificant. Throw me a bone here!

Hanif08, thanks for the link. I'm looking for something a little less verbose though. If anyone else has a suggestion let us know. Sorry for the rant, but y'all asked. Thanks for the replies thus far.

 

[jike]

I haven't work in foreign countries in recent years so I am not sure what tools you have available. For the US, I often go into mapquest, terracon or other similar programs to see what the situation is with surrounding buildings and obstructions to help develop an exposure catagory.

 

[swearingen]

I'm dismayed at your statement that you don't know the local code. You need to get to know it or find someone who does. You dismissed my suggestion and said that you'd much rather them tell you what the exposure category is.

If it is in another country, how would you expect a non-civil engineer to know what an exposure coefficient is? What's more, how could you expect a local civil engineer to know what that is? He probably has never heard of the term. His local code may not use them.

You have two choices:

1. If there is a local code - learn it and use it.
2. If there isn't a local code, find out what you can use and suggest using one you know.





If you "heard" it on the internet, it's guilty until proven innocent. - DCS

 

[hokie66]

dozer,

Your frustration is well justified, but unfortunately that is the nature of doing work in different countries. I don't think making a fill-in-the-blanks form will do much good, as the terminology varies. To do it right, and assuming the country you are doing business in has a comprehensive code or standard for loading, you really need an engineer conversant with that country's practices to develop the loading information for you. If it is a developing nation without its own statement of requirements, the usual rule is to try to gain acceptance to use your preferred standards. You would still need to make a logical assessment of the exposure conditions.

 

[dozer]

Swearingen, I didn't dismiss your suggestion, I disagreed with it. There's a difference. Let me try and explain my position again. The company I work for is usually one of many working on a large facility. The owner has hired a consulting engineer to write specifications for the work we all do. My only point is it seems silly for each subcontractor to guess at things like exposure category (assuming the building code has such a thing) when the consultant could just put in the spec.

There are two reasons this makes sense to me. First, during the bid phase the tighter you write your spec, the more even the playing field will be and the fewer surprises you will get down the road. When the shoe is on the other foot and I'm writing my part of the spec for say the air coolers, I don't want this stuff to be left to chance and I spell it all out. I know plenty of vendors who will assume category B figuring their cost, win the job, say "Oh, why didn't you say category C? That will cost more." Why not just shut that door from the get-go and avoid the headaches?

The second, is really the same reason, but from the other perspective. Say I, in good conscience, use cat. C. I submit my calcs and the consultant, for some crazy reason, says "Resubmit with cat. D". Now you're in a pissing contest. Again, if he would have just been complete, it would have avoided the whole mess.

As far as me "not knowing the local code", in the example I used, I was asked to comment on a spec we got for a job in Russia. I've never worked on a job in Russia, so at the time I was asked I wasn't familiar with the SNiP code. Why this "dismays" you is beyond me. I bet most of the people reading this don't even know the Russian building code is called SNiP.

I have since read the part applicable to us and I have a passing knowlege of it. Though I must say the English translation is terrible, but that's neither here nor there.

Hokie, yeah, I just think the "cheat sheet" would work for U.S. codes. To try and cover all the codes beyond our shores would be too much.

 

[csd72]

dozer, try to use a number of terms on your 'cheat sheet' so that the type of information required is clear.

Also on the cheat sheet the first item probably should be design code - let the consultant specify it.

I understand your frustration with sales people, this is part of the reason why I no longer work with companies big enough to have one.

swearingen,

Your comments clearly indicate that you have no experience in the type of work that dozer does. When designing small components of a project, it is not your role to determine wind criteria - only to confirm compliance with the given criteria.

 

[swearingen]

As a matter of fact, csd72, I've done work coast to coast and in other countries in petroleum, chemical and bulk handling facilities. I do understand what's involved.

I think there's two issues here, only one of which the OP is complaining about:

1. Loose specs that do not define variable terms that show up in the codes.

2. Requesting and using the code appropriate for the country/region that you are designing for.

Addressing Item 1., I smell what he's stepping in. It is common and often happens within U.S. borders, let alone other countries.

It is item 2. that dismayed me in the OP's second post. It just appeared that he's expecting everything to conform to codes he's used to, which may not be the case when doing work in another country. I'm comforted to know that he has a translated copy and is getting up to speed.



If you "heard" it on the internet, it's guilty until proven innocent. - DCS