Unknown joist call out

[Runmdc]

I have run across some unknown open web steel joists and the call out on the original drawings is 18H192/80. They were built in the 1980s. I know that they are 18H joists but what I do not understand is the 192/80. Is this DL/LL or does it designate Total Load/LL? What confuses me more is that if I subtract the 20PSF for LL the remaining available load is under what is actually field verified. I have never seen joists called out this way. Can anyone help me with this? What do the numbers mean?
On a side note the joists were manufactured by Tex-Ark. They have been out of business for 20 years so I have hit a dead end there too.

Thanks

 

[sonofamsquared48]

You can contact SJI (steel joist institute) which holds an archive of old steel joist catalogs. They are quite helpfull and can even send you the cut sheets. It is hit and mis because they are not the library of congress, but it is a great resource. I typically specify steel joist this way: joist designation, total load, live load. Often the total load is amplified a little to accomodate for future mechanical allowance (usually at the roof). I am not sure what you mean relating to "field verified". can you be more specific, or word in another way.. Hope you the best, cheers.

 

[JAE]

It should be an 18" joist with
TL capacity = 192 plf
LL at L/360 deflection = 80 plf

 

[Runmdc]

I figure that the total load is 192 and live load is 80. The design roof live load is 20 psf and the joists are 4 ft. OC. At this spacing the design live load is 20X4=80plf. This means that the allowable dead load is 192-80 = 112plf. If the allowable dead load is 112 plf, that is only 28 psf. Even with a 3 inch topping slab that is lightweight concrete that makes up the entire 112 plf leaving no room for any other dead loads. Seems wrong to me, there has to be more capacity than that.

What i meant by field verified was that I know what the actual dead loads are. And they are greater than the 112 plf I describe above.

I tried contacting SJI and they say they need the member measurements. I am trying to avoid doing this because of cost to the client but I may have to do it anyway.

Thanks

 

[JAE]

I suppose the 192 could be dead load instead of total load but I'd need more info to guarantee that. Your initial calculations certainly suggest 192 dead (i.e. 48 psf).

 

[hawkaz]

JAE is correct- The standard callout is TL/LL

Are you sure that this is lightweight concrete and not lightweight insulating concrete? Big weight difference.

 

[msquared48]

I would have to agree with Hawkaz. It would seem odd to use normal weight concrete on a roof. Floor, yes.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[MiketheEngineer]

Having "reverse" engineered a number of these - it is most likely right on the "money" with little or no margin for error or "extras".

That is often why you will see weird on center spacing - like 5'-3.5'' or some other silly dimension. The joists are completely at their design max.

 

[Runmdc]

Is there a way of telling if the roof is lightweight insulating concrete or just lightweight concrete?