British Code vs IBC

[mrpid]

I work in the US and I am currently packaging a cost estimate for a structure in South America. According to the specifications supplied they will be using British Standards/Codes. At this moment I have zero familiarity with the British Codes and I am curious as to the differences between design criteria, specifically wind and seismic. Is there a difference in steel shapes/sizes? Where would I find a good single resource without purchaing serveral codes?

Thanks in advance.

 

[Ussuri]

A few starters:

1] Typically UK codes are Ultimate Limit State which is similar to US LRFD, one notable exception is timber which is still permissable stress.

2] Section sizes are completely different, as are designations. See:

thread507-215417

thread507-214884

3] UK wind codes are, strangely, UK specific. I doubt they will prove very useful to you in South America. I guess you will need to find out how they cover that locally.

4] Seismic design is not that common in the UK. Certainly run of the mill structures are not designed to resist earthquakes. We dont get many and they are pretty feeble.

The UK is moving towards the Eurocodes which does cover seismic specifically.

If you dont want to buy the codes you might think about a subscription to BSI Global. You can get access to the standards online.

http://www.bsi-global.com/

 

[Ussuri]

I suppose I should have added:

Steelwork - BS 5950
Concrete - BS 8110
Water Retaining - BS 8007
Masonry - BS 5628
Timber - BS 5268
Foundations - BS 8004
Loadings - BS 6399
Dead Weights - BS 648
Steel Grades - BS EN 10025

 

[mrpid]

Thanks Ussuri,

This will be steel and concrete, so I will not worry about the timber.

I had thought the shapes were different but I could not find the thread.

I typically use IBC, International Building Code, which is strangely US Specific (there are not any world maps for wind or seismic coefficients...should be called USBC) I have a couple of coworkers visiting the job site this week and the wind/seismic load was on my list of questions.

Again thanks for the link. And the list of specs will aid in my search.

 

[mrpid]

Another question: Are there different concrete reinforcemnet designations and grade? In the US we use #3,#4....#14 which typically has a yield strength of 60 ksi and the diameter for most bars is such that a #3 bar is 3/8" dia. and a #4 is 4/8" or so forth? (This does not hold for larger bars)?

 

[youngstructural]

The concrete grades and bars will be metric....

Concrete will be in MPa (N/mm2). Typical strengths are 25, 30, 40 & 50. The conversion is psi*6.894757MPa/1000psi

Thus for 4000psi ~ 27.5MPa

Rough equivalence (VERY rough, you can't just convert a design) is available on lots of sites. Wikipedia actually has a pretty good article on Rebar, if not very technical and not especially useful for seismic considerations. Check out

http://en.wikipedia.org/wiki/Rebar

Pretty sure that 300MPa & 500 MPa reinforcing is available on the international market. You'll definately want to see what's available locally before you start your design.

You will probably be expected to produce metric drawings. Being a Canadian engineer and having practiced in both systems of units I would strongly encourage you to make the change over at the very start and design everything in metric. It will save alot of headaches!

Good luck!

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[mrpid]

Thanks YS,

Currently I am putting together a proposal and quantity take-off, so I am doing a generic design using imperial units (Quick and easy). I appreciate the advise because my mind set tends to do the design imperically than convert to metric. The metric system is logically a better system; however,when all you use are English units it is hard to do otherwise. You are correct about the documents, everything shall be done in metric units. I am looking into what is available(both reinf and steel shapes).

Again, Thanks for advice and the luck!

 

[youngstructural]

Glad to help. I know how difficult the change over between systems can be; A good trick is to work out your "gut feel" loads in your more familiar system, then convert them. Work out your actual loads in the system of measure that is standard for the project, but use your "gut feel" cheat sheet as a check.

If you're not familiar with Metric, you might stumble. Producing your own cheat sheet makes it more likely that you'll catch the goofs. We're all human!

Hope you get the job, the project goes well and the metric change over doesn't get you down. *smiles*

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[rapt]

One thing not mentioned is that concrete strengths in BS codes are cube strength while US is Cylinder. Cylinder is about .8 * Cube.

I thought IBC stood for IntraNational Building Code as it is only written for USA and is not recognised by anyone else of any significance!!!

 

[youngstructural]

To their credit, the International Building Code is INTENDED to be without any specific jurisdictional limits... The only problem is it is by nature american, being both in Imperial measurements and with wind, seismic, etc provisions that only work in the US.

I'm Canadian, so I'm the opposite of biased towards the US, however this naming isn't a result of arrogance, it's the result of over-shooting the mark and underacheiving in order to ensure that US engineers would actually behave when their jurisdiction adopt the code.

And DAMN good point re cube strength! It's actually common to use cylinder strength outside of the UK, as best as I know. Although Metric countries, Canada, New Zealand and Australia all use cylinder strength as standard practice. The South American country in question could very well do the same.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[Ussuri]

YS,

Cylinder strength is used in Europe, cubes are a UK thing.

mrpid

If you are speccifying concrete you should also look at BS EN 206 (specifying concrete) and BS 8500 (the complementary specification). Reinforcement is BS4449:2005.

http://www.ukcares.co.uk/

This website gives some free guides giving information on reinforcement. They are slightly out of date as they refer to BS 4449:1997.

http://www.cementindustry.co.uk/

http://www.cementindustry.co.uk/concrete/specifying_concrete.aspx

They have some publications for downloads

http://www.concrete.org.uk/default.asp?submenu=home

You may have to join to get anything from this one.

http://www.concretecentre.com/main.asp?page=0

They have some free stuff. You have to register though.

http://www.steelbiz.org/

This one is steel related.

 

[apsix]

Using British codes for design shouldn't have to mean that British codes for materials are used.
It would make sense to use what is available in the country, provided it can be shown to be of adequate quality.

 

[mrpid]

Thanks again for the advice. One advantage of the IBC is that has been adopted by many states/jurisdictions so it minimizes the need for multiple building codes within the US; Florida, however, seems to beat to their own drum. I am sure there are some other solo artists out there, but they do not come to mind!

 

[csd72]

One thing that may be an issue, the british code is set up for a cold weather country so the minimum reinforcement rations are based on frost cracking prevention.

These ratios may be a bit over the top for south america.

The UK codes are also based on a different wind return period if I remember correctly so this needs to be taken into account when analysing wind data.

Just remeber that local practices and material availability will dictate design, these will be very different from the US.

 

[rapt]

youngstructural

You are being nice to your neighbours today. National or Uniform might have been reasonable names. To call it International tends to mean what it says. And it will never be accepted internationally.

mrpid,

An easy solution would be to make control of and acceptance of such a code the responsibility of the Federal system rather than local counties. Then there is not a plethoria of codes and a building on one side of a line on a map would not fall down if the line was moved to the other side of it. Probably too logical to do!! And then George W would have control of it too!

If you are designing to BS code then you cannot ignore BS material specifications. Reinforcement specs and concrete properties must conform to the BS codes to be used in the formulae and design methods in BS code. Otherwise adjustments need to be made. eg, shrinkage of concrete could be completely different in the country you are designing in so span/depth ratios which are affected by shrinkage would be affected by different materials, unless you use more accurate design methods like Part 2 of BS8110 as RAPT software does.

RE minimum reinforcement rules mentioned by csd72, the British minimum reinforcement requirements are actually very low (.0013 for slabs) and should be increased unless very low strength concrete is being used. The code writers forgot to make this value dependent on concrete strength

 

[csd72]

rapt,

It has been a while since I used the BS, all I can remember it that it was very frustrating having a code that said 'minimim steel must be x' without any regard for restraint, exposure e.t.c.

I think they use the IBC in puerto rico too, does that make it international? I kind of think of it like the world series in baseball.

 

[youngstructural]

rapt: I always try to be nice to my neighbours. Particularly when they are generally well intentioned, generally well meaning, and generally a whole hell of a lot bigger than me. Also when they are specifically stunted in their outlook it doesn't help to point it out anyway so why bother?

In all seriousness, I know a great deal of very good Americans who are ashamed by what has gone wrong with what (I hope to think) was well intentioned actions. And I'm talking about people on both sides of the Red/Blue debate. I don't think we would do any better job running the world, and I think that mostly other counties did a WORSE job than the US. That said, I DO know what I DON'T like, and sadely I see a lot of it these days. Pity really.

csd72: Hahaha... Puerto Rico and the other US "dependant teritorries" always used to make me laugh... Now I think I prefered the smoke and mirror version of US imperialism to the reality we face today. And no, just like your sarcasm, Puerto Rico doesn't make it so. But it was the INTENT of the code committee. They must have forgotten that the rest of the world's engineers gave up measuring with body parts and bags of food a while ago.

I suppose this is the least productive and technical post I've made in a while... Oh well, we'll see if it survives. Hopefully we don't loose the whole tread for my sins!

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[apsix]

The idea that one country can call their code international has merit.
Think of all the money that would have been saved if the EU saw sense and just used the BS's as EuroNorms, rather than the endless meetings trying to get the Brits to agree with the Italians to agree with the Germans etc.

 

[rapt]

csd72,

You forgot Guam.

The BS8110 minimum reinforcement limits have nothing to do with restraint. They are simply to provide minimum ultimate capacity.

If you have restraint, you have to calculate the effects and the reinforcement required to control the cracking.

apsix,

Yes the Eurocode "model codes" concept has become a complete mess with about 20 different codes based on it all giving completely different results because noone could agree at all of those expensive meetings, though I would not have based it all on BS8110 as an alternative. It has major problems in some areas also.