Structural Analysis

[EricaB]

My company is looking at an existing steel structure to determine if it is capable of handling increased loading due to the heavier equipment being installed on the operating deck.

The steel structure was originally designed and constructed in the 70s using A36 steel, ASD design to the 7th edition steel manual. We have CMTRs for all of the steel used in the building.

We have run into a situation where we need to either reinforce certain beams under the new equipment per the analysis using fy=36ksi or sharpen the pencil in the analysis. When reviewing the CMTRs for the steel, the steel averaged > fy=42ksi. When using the CMTR reported yield strength of the steel we limited the number of modifications to the existing steel.

Any guidance on whether this is a code accepted practice? Do we need to do some form of destructive testing to verify the yield strength of the steel?

Thanks.

 

[dcarr82775]

I can't speak for the Nuclear world, but whenever I touch/modify a building component U use the latest Code (or at least the one adopted by the local Building Dept). I don't think it is proper to use the 7th Edition if you are actually changing the conditions in the Building.

 

[EricaB]

That's where nuclear is tricky, we have to go with the licensed code of record, which per our license is the 7th edition. Typically, for new design we always use the current code, but for the existing stuff we don't go back and reconcile the design to meet today's code requirements.

 

[rb1957]

'planes are the same ... when you modify a plane you (generally) use the requirements at the time of certification. the logic to having a "basis of certification" is so the manufacturer is trying to hit a stationary target on a project that lasts several years; you couldn't accomodate a rule change late in the design process. then for modifications the idea is "if the rest of the plane is designed for X, where's the increase in safety if this (small) change is designed to Y".

for this reason (like it or not) most of the 737s flying today are certified to 1960s rules (with some updates, like fuel sys, cabin sys, ...). Boeing might have updated the basis of certification for their latest model, but i'd be abit surprised if they did; not that they're doing anything Wrong.

 

[ToadJones]

thanks, I already hated flying.

 

[azcats]

@JAE Thank you for originally posting it. I've used that reference often in the last couple years.

And no worries AUCE98.

 

[DWHA]

EricaB,
I do not know of the top of my head where it is stated. I just know I had an action that was due today (2/17) to review all pending modifications for the use of CMTRs and create additional actions as req'd.

Have you tried an OPEX search for CMTRs? If I get some time, I will do some digging and see what I can find. Good Luck!!!

 

[paddingtongreen]

The nuclear business is strange. Much has been done, as EricaB says, to the original code, but when we were re-qualifying piping and cable tray supports years later, that work was done to the latest codes. Of course, the loads were different because of better software and updated earthquakes.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[EricaB]

We always have the option to reconcile the differences between the codes.. on a lot of stuff, like cranes we have, but on things like piping and steel, we do not... however, we do use the latest codes for new design on some things...

At least I don't glow in the dark.

 

[steellion]

"At least I don't glow in the dark."

...Yet.