where can I get idea about stresses in beams?

Answer 1

It depends on what you want to know and how you intend to use the beam. The calculations for stresses in beams are pretty mind numbing, but all you probably want to know is "will it do the job?" For home construction you can get information on beam sizes and spans for particular applications from your local uniform construction codes, timber framing codes etc. Look them up on Google. For steel beams you can usually get a span table for different beam types from the manufacturer's website. In both cases they give you maximum spans (between points of support) for particular sizes and shapes of beams - for particular applications. They're really based on what is known to work in most common situations. Remember, these codes are based on typical building practices that ensure uniform distribution of loads, proper restraint (and correct stress grades for timber). Use the codes to get your thoughts together and then talk to someone in the building game before you start. If you are into lifting engines out of vehicles or building bridges etc then these codes won't be much help. You will need to get an engineer to work it out. Beam restraint and load dynamics become very important and any mistakes can lead to a sudden failure, particularly with light C sections.

Answer 2

Look up bending and shear stresses.

Answer 3

Refer to a book "Strenght of materials".