Concrete on Metal Decking dead Load Question

[aswierski]

I'm working on a structural remediation of a library and have been supplied live loads and steel member sizes to determine my dead loads for temporary shoring. The client wants to remediate by reinforcing the underside of the second floor, so temporary shoring will be required. Now, the drawing that was supplied to me for reference calls out 2.5" OF CONCRETE OVER 1.5" METAL DECK; TOTAL DEPTH = 4". For now, I'm assuming the concrete to be 150 #/ft^3. What should I use for the metal decking weight? Does anyone have any good tips? Should I just calculate a 4" thick slab of concrete and go with that? All suggestions are appreciated, and sorry for my ignorance. I'm a new engineer without the benefit of a Civil or Structural P.E. in my office, so good advice has been hard to come by. (My employer has told me for the past year and a half that they have been trying to find one...)

 

[lkjh345]

A Vulcraft metal deck catalog has weights for various decks sizes and concrete fill combinations.

Assuming 1 1/2" composite metal deck with 2 1/2" normal weight concrete fill (4" total), the catalog gives a dead load of 39 psf.

 

[hungnguyen712]

If you don't have a PE there, give Vulcraft's PE a call to help you through designing their product. They were very helpful when I had to do my first metal decking.

 

[SlideRuleEra]

IMHO, there are too many unknowns to use precise numbers. For example:
1. Manufacturer of existing metal decking (actual dimensions used)?
2. Actual weight of concrete used?
3. The true thickness of the concrete, not the theoretical thickness?
4. Do you have "design drawings" or "as-built drawings"... there may have been changes?

Also consider ZTENG's advice about possible LL.

For the weight of the concrete / metal decking composite (by itself) I would assume the 4" of concrete (50 psf) that you have proposed.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[msquared48]

Another issue for you to think about here - with no PE in your office, if you are trying to accrue time in grace so to say so you can take your licensing test, the time spent here without the direct supervision of a licensed PE will not be countable time on your application.

This will delay your professional timetable.

Mike McCann
MMC Engineering

 

[paddingtongreen]

I'm interested in what remediation means in this case, and how you are going to do it.

I would use the 39#, it won't be much heavier if at all.


I usually put a 40# construction load on a new slab, but you will be underneath it, so I don't know.

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

 

[aswierski]

Thanks for all the great replies, gang. I'm in a crunch to get some design deliverables out today, but I'll be sure to post back tomorrow with some more explanations...

 

[MiketheEngineer]

I like the 50 psf...

 

[beton1]

What is your shoring bearing on. Maybe I am looking too 'far' into the question. (I would also go with 50 btw)

 

[nuche1973]

Does your shoring drawing need to be sealed? If this is the case I'd hire one of the national shoring/scaffolding companies like Aluma, EFCO, Patent and have their engineers figure out the weights. Also, another issue to be aware of is the "engineering with-out and engineering liscence" topic. If something happens you could be in alot of trouble, remember CYA.

 

[csd72]

A conservative estimate is to treat it as 4" solid concrete.