Any body can explain :
1. what is modal participation factor
2. how is it used
3. how to calculate it
4. good/simple book that detailed modal participation factor.
the modal participation measures the coupling between the exciting force and the given mode shape.
for example, if you have a uniformly distributed excitation force and you want a quantifiable measure of the coupling to each of you modes then modal participation is proportional to the integral of (force) x (mode shape). normalization insures that the maximum value is unity.