Concrete Between Steel Beams 1

[VBI]

I am investigating a 1-story structure that has 3 bays with (3) W12x22 beams runing 250" long 6'O.C.. 12" thick concrete is located BETWEEN the beams. When I analyze the steel, it is insufficient to support the concrete as a dead load + live loads and I believe that the concrete is actually working as a beam (self sufficient) in the long direction.

Can anybody offer any advice as to how I would make this determination? I am trying to show that additional dead load could be hung from the underside of the steel beams but it is not possible if the beams are supporting the dead load of the concrete placed between them.

THANK YOU for any help that could be provided...

 

[DRC1]

Why not jack the three beams and measure response to a knowmn load? that way the actual beam stiffness could be determined to decide the capacity of the components. Measurement of existing deflections do not help unless you know the actual pre pour camber.

 

[msquared48]

DRCI:

This is probably an obvious observation to all, but I thought I'd better mention it anyway...

If you do jack the beam, I would suggest jacking, or loading the beam in the upward direction, not down. The beam Will have more capacity in this direction, and be less likely to be distressed by the test.

Mike McCann
McCann Engineering

 

[haynewp]

DRC

I thought about that after I posted, and even if it were cambered for the slab weight and settled down to horizontal currently, then the ultimate strength of the floor is the same but the total deflection would be different. I think he needs to find out if there is any reinforcing in the concrete and look into the strains of the system to make a decision on capacity. Shored or unshored, I think you have the same ultimate capacity if the strains permit.

Serviceability issues need a look into current deflection.

 

[haynewp]

Regarding slab jacking, I was thinking about this and the shored/unshored question I believe would make the determination of capacity from jacking the floor upwards unclear. The reason I say it is unclear is that if the slab has reinforcing it will be in the bottom of the slab, so the upwards response of the originally unshored floor would be different than the downwards response going past the self weight deflected position.

I also am not sure how I feel about forcing new deflection in the downwards direction without first knowing more about what is going on.

 

[wbmartin3]

Ok, I may be just a little bored out of my mind and as the son of an aerospace engineer, I'm wondering if I should change directions. I just a bit of a geek ... maybe a lot of a geek ... a Realtor after 20 years working in the medical and pharmaceutical sciences (BS Biology, UC Irvine) and MBA (East TN State U). Any suggestions? Is it worth the time (I'm just 50).

 

[msquared48]

On the average, it would take you a minimum of four years in school, four years experience before you could take your PE (Civil), and another one or two years before you could qualify to take the Structural test - 9 to ten years.

How long have you planned to live past 59? Then again, if you are bored and single, maybe the college life... Let's not go there.

Mike McCann
McCann Engineering