The design process for a beam can be summarised as follows:
a) Determination of all forces and moments on critical
section
b) Selection wood type and trial size
c) Classification of section (I, S, A)
d) Check shear strength; if unsatisfactory return to (b)
e) Check bending capacity; if unsatisfactory return to (b)
f) Check deflection; if unsatisfactory return to (b)
g) Check bearing at supports or concentrated load; if unsatisfactory provide incrased bearing
h) Check connection details
i) Summarise results
shear fv = VQ / Ib
bending Fb=Mc/I
Beam deflection for floor beams (with plaster clg) is limited by UBC and SBC as 1/360 of the span length for LL and 1/240 for DL+LL. Beams W/O plaster clg L/240 for DL and L/180 DL+LL