Maximum deflection in a timber beam

nick.w

1. The problem statement, all variables and given/known data
Particle board flooring (dead load 8 kg/m2 including joist self-weight) is supported by a series
of Radiata pine VSG8, of call size 150 x 50, timber joists running parallel to one other at 450
mm centers and spanning L=3.8 m between supports. The floor supports an imposed load
of 3.5 kPa.


Assuming strength requirements are OK (they may or may not be), what would be the
maximum deflection (in mm) of the joist?
Assume allowable deflection for the joist is L/350. Is the calculated deflection
acceptable?
NOTE: for this calculation use w = 1.0 * Dead + 1.0 * Live
(use gauged, kiln dried section size for timber section)


2. Relevant equations

Max Deflection = 5wL4 / (384EI)


For the above formulae:
L is the length of the beam,
E is Young’s Modulus (Units Pa, MPa, GPa)
I is the Second Moment of Area of the cross-sectional shape of the beam (units m4 or mm4)


3. The attempt at a solution

I think this is the correct formula but need to be certain. Also how do I find "I" if this is the correct forumla.

I also get thrown off by. "use w = 1.0 * Dead + 1.0 * Live" as I have already calculated the UDL in an earlier part of the question using w= 1.2*dead + 1.5*live.

If you guy could point me in the right pirection of which formula to use I would appreciate it.

Regards,
Nick

nick.w

edit: Just been having a flick through the forums and wondering if I might of put this in the wrong place. Please move if so. Cheers

nick.w

bump? More info needed?