huangyhg

concrete slab design
i am a relatively new civil engineering technologist, and i was ust wondering what the best way to design a concrete roof slab supported by walls, with 3 feet of soil on top.
thanks
1. factor the loads.
2. draw the shear and moment diagrams.
3. check shear and moment.
4. check deflection (usually doesn't control with concrete).
5. check bar development lengths.
6. check cracking (bars spaced 12" oc should satisfy this).
daveatkins
the first step i would do is to go to the aci code chapter 9, table 9.5 (a, b, and c) and get a minimum thickness so that you don't have to worry about deflections. that gives you a starting point for figuring dead loads. then follow daveatkins procedure and you should be fine.
if you can avoid it, don't rely on the concrete as the waterproofing (if you require waterproofing).
i suggest that you hire a competent structural engineer to do the design for you. roof slabs carrying loads is not a simple task and there are many other issues that you need to worry about besides structural such as corrosion, moisture/water intrusion etc.
regards,
lutfi
lutfi is exactly right.....with all due respect, drf9984, i doubt you are qualified to perform such an analysis and design. if you are seeking such so as to be better prepared in dealing with engineers in your firm, then i applaud your efforts. if you are working in a firm where you are expected to put forth such a design, then that firm should re-think its mode of operation.
depending on the slab geometry, you could have a one way slab, a two way slab, or consider it as a plate. the slab to roof connection will influnece the design, simple support or integral.
check with the grey-beards in the office, see if they any "coldies", prior designs to follow.
best, tincan

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