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

Model

Model

FEA mesh

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.

Self weight

Dynamic analysis

Mode 1 - 29hz

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