Beam on beam Analysis

[LF97]

http://www.eng-tips.com/viewthread.cfm?qid=110626

Hi,
I was reading the above thread and was unsure about how to go about calculating the bending stresses in such a system where the beams are unconnected. When carrying a lateral load causing a sagging moment, is the bending moment in each beam equal and does the maximum bending stress occur in the weaker beam (assuming beams have different moments of inertia).

Thanks in advance

 

[KootK]

You split the moments to the two beams based on relative EI as discussed in the other thread. After that, you simply calculate the stresses in the usual way (Mc/I for each beam individually). The maximum bending stress will occur in the beam for which the distance from its own neutral axis to its own extreme fiber is the greatest. That will most often be the stiffer and stronger beam.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.