SLAB design

[serenade]

where should i start in designing a concrete slab? and what considerations should i note first? what method would be best to be used since i still dont have a prgram for that and this is my first time to design in actual. (i have just graduated last may and my uncle asked me to design the slab - i was applying and he gave it to me [3-storey], the baylength is 4X5, 3m-2m-4m-2m-5m on the longer side and 3m/bay on the shorter side).

thank you for any help you could give.

 

[Bbird]

Go and get yourself a copy of Reinforced concrete designer's handbook by CE Reynolds & JC Steedman. In the text there are tables of bending moments for slabs supported by different arrangements.

British code on RC design also gives tabulations and Roark's Formulas of stress and strain by WC Young has a full section on the bending of slabs.

Reading them together should give you a good feel about the problem.

Always think and reason it out like an enigneer. For example if slab is long in one direction then the moment at the support and midspan should approaching those of beams.

 

[tincan]

Another source is the CRSI Design Handbook (Concrete Reinforcing Steel Institute, Chicago, Ill.)

 

[cvg]

you will need some data on the foundation including:
type of soil, compressive strength, depth to water table etc. Look for a geotechnical (soils) report or consult with an engineer to do an investigation and report.

 

[chicopee]

Designing the slab is found in any text book on foundation and soil. The biggest challenge is to determine the loads on the slab which will impact the concrete. For example do you have wheeled machinery operated or parked on the slab. Such equipment will cause concentrated loads whereas if you have stored stock you will have evenly distributed loads.
Above responders have it right w/ references and the geotechnical report of location.
If it is just a slab with no reactions from water table, foundation walls and footing, frost heave and knowing the loads from equipment and stored material, you can make a first estimate by using the architectural standard section on slab showing total loads vs. loaded areas for thicknesses from 5" thru 8".
Good luck.