Calling out old, existing steel

[mtu1972]

We are working on a retrofit to a 1969 era industrial plant.

The existing steel is being called out with their original designations, i.e. 12B19, 14WF34, 15I42.9, etc. I think we should use the current section calls - W12x19, W14x34, S15x42.9 etc., but am in a very small minority.

It was pointed out that this way they (Contractor and detailers) will know it is old steel. I feel one additional note could convey that same information regarding any "existing" steel. The line weights will deliniate new vs. existing.

Please let me know if you have run into this and how you (or your companies) have handled it.

Thanks.

gjc

 

[BadgerPE]

If you have verified the properties of the new designation are exactly the same as the new ones, then I would tend to agree with you. However, maybe so it is clear to everyone, you could maybe say "Existing 12B19 (W12x19)".

Just my 0.02

 

[BadgerPE]

If you have verified the properties of the new designation are exactly the same as the old shape properties, then I would tend to agree with you. However, maybe so it is clear to everyone, you could say "Existing 12B19 (W12x19)".

Just my 0.02

 

[EngineeringEric]

In the past i have always called them out as existing 12B19 and did not convert it to W12x19. I typically add a note that states the existing beams were not verified and should be field verified....

I don't think it is right to convert the size without confirming... and i do believe some one the parameters are different than modern sections of equivalent weights. But we are talking about slight variations so use your judgment.

 

[msquared48]

By all means, always call it out by the old designation - there are steel books existing that show all the properties. Plus, the grade of steel for the older sections was different than present day sections.

Mike McCann
MMC Engineering

 

[SlideRuleEra]

I agree with msquared48, also, there are other reasons to call out the old steel by only the old designations:

1. Not all old sizes have identical (or even similar) equivalent new designations. Perhaps they do on this project but that is not always the case.

2. If you do label the old sizes with new designations, the Contractors and Detailers may assume that sometime between 1969 and now the old size members were replaced with a newer members. This may not cause a problem, but why risk it?

3. Why should you assume the responsibility for "translating", with complete accuracy, the old size designations into new designations? AISC Design Guide 15 is a good reference for the old member's properties.

I recommend calling out the existing members by the designations that they had at the time of installation. Having a note explaining this is a good idea, but stop with that.

http://www.SlideRuleEra.net

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[paddingtongreen]

Use the designation on the original drawings, why would you want the extra work and the extra risks if you get it wrong?

There was a huge shape change made, I think in the very late seventies. Designations and dimensions were changed, some were big changes, some were small, some were only in name.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[JAE]

Use the old shape names.

You are not correct that a 12B19 is the same as a W12x19. They many times have different properties and geometry.

 

[mtu1972]

OK - I was wrong. But, there was already extra work as the old shapes were not in the CAD database - so they recreated them for the 3D model.

I still fully expect RFI's from the Contractor asking "What exactly is a 'B' section?"; etc.

Thanks for all of your help.

gjc

 

[NITTANYRAY]

The shape sizes changed in the 7th Edition (1970)
The web thickness of a 12B19 is 1.2% thicker than a W12x19 and Rx is 1% smaller than the same values for a W12x19. In other beam sizes the weight increased or decreased from previous sections.
The changes were made to standardize how sections were rolled and make production more efficient. The inside distance between flanges of groups of sections are all the same and beam weight & strength is increased by moving the rollers on the top and bottom of the flanges outward. Notice the "T" value in the dimension and properties tables. A lot of the old B and M shapes did not have the same "T" within the same groups.
The 12B19 had a "T" of 10 3/4". The W12x19 changed to 10 3/8" in the 7th Edition. For some reason it is shown as 10 1/2" in the 9th Edition manual but is now shown as 10 3/8" in the 14th Edition.