HOUSE DECKStructural Analysis
12/31/2015
Don Blanchet
3B Associates
Assumptions
New construction to MA codes
No break out stress cracks
No insect damage
Model – 12 foot x 12 footfloorplan
Lumber
2x12 framing4x4 support posts8” dia footings6x1 planking2x4 railings2x2 spindles
Assumed Wood mechanical properties
Loading
Self weight gravity
Snow loading
Dense party static load
Dynamics dancing at natural frequency
Dancing loading approximation
Apply harmonic force wavelets to areas of the deck planking over the range of 40 to 200hz. Peak force of 500 lbs.
Mode 9 – 70hz deck surface springing
Dancing dynamic loading response ringing at 75 hz
Snow load maximum stress location
Results Summary: 12x12 deck
loadingMax
Deflectioninch
MaxStress
psi
Factor of safety
Gravity1G
.003 22.0 154
severeSnow(2 psi)
41,000 lbs
.188 1194.0 2.84
Party10 people(1800 lbs)
.010 70.0 49
Partydancing .060 400.0 8.5