is 56 ft span slab can be designed w/o using pre/prestress option? 1

[yjung]

Hi all, again,

I have 56 ft span one-way slab with 10 ft soil cover including 2 ft LL surcharge, a lot of dead loads on top of the slab. i have only 30 inch thick for slab design. The slab is supported by drilled shaft. (Acting like frame) No column in middle of the slab.

I have tried everyway to design the slab. it never worked. All kind of option i used did not work. (kind pissed me off) The slab moment was about 300 k-ft/ft. Using high strength concrete never helped for moment design, but increased allowable stress only. Doublely reinforced steel never help, it even reduced the "d". Using stiff column with reduced slab thickness never worked. I wanted to distribute the dead load to column more. It never worked that way. and so on, and so forth.

Is it possible to design this slab without using prestress option?

Or slab can use bundled bars?
The minimum distance between the bars can be reduced to 1 inch?

Please advice me.

 

[wiktor]

yjung:
instead of using regular rebars use T or H or W embedded in the concrete. The best could be to use closely spaced inverted T's, with drilled holes in the webs, to accomodate transverse rebars. The design procedure is somehow similar to the RC concrete design. Calculate the DL deflection and camber the slab accordingly.