Nature vs. Nurture – Defining the
Character of Deconstruction Lumber
Paul Crovella
Deconstruction Summit – March 24, 2011
What am I
doing here?
Basic Research Question
• Variability in fresh sawn
lumber comes from
forces of nature and
genetic diversity.
• Variability in
deconstruction lumber
comes from the above as
well as the load history
• How much greater is the
variability in
deconstruction lumber
than fresh sawn lumber?
Wood Handbook - FPL-GTR-190
Non-destructive testing
• What are common techniques to determine
material properties non-destructively?
•
•
•
•
Visual Evaluation
Measured density
Measured dynamic stiffness
Measured static stiffness
Visual Evaluation
History of Lumber Sizes and
Grading
• Construction lumber size
standards were first
published in 1924 and
revised in 1926, 1928,
1939,1953, 1964 and finally
1970.
• In 1924 the ALSC produced
the first national standard
for lumber grades, uniform
strength values were applied
in 1944
Demographics of Syracuse Housing
1980 to
1999
1960 to
1979
1940 to
1959
1939 or
earlier
Modern Visual Grading
• Typically separated by
Species and Region
• Species are mixed if
they have similar
strength properties
• Surfaced material is
inspected with by a
trained inspector under
controlled conditions.
Image from Buffalo Re-Use
MOR Testing – Modified ASTM D198
(single point)
Stress vs. Strain - Board 18
14000
Stress σ (psi)
12000
10000
8000
6000
4000
y = 608390x - 241.78
R² = 0.9998
2000
0
0
0.005
0.01
0.015
Strain ε (in/in)
0.02
0.025
Density to Strength?
MOR vs. Specific Gravity
Specific
Width Depth Length Weight Gravity
(in)
(in)
(in)
(lb)
G
1
2.000
3.750 98.750
11.11
0.415
2
1.500
3.688 80.000
6.55
0.410
3
1.500
3.500 93.250
10.51
0.595
4
1.625
3.813 92.125
11.60
0.563
5
1.500
3.500 87.750
8.76
0.527
6
1.500
3.500 82.000
8.27
0.532
7
1.750
3.625 85.000
11.75
8
1.750
3.750 96.000
11.92
9
1.500
3.375 80.000
7.78
10
1.750
3.750 86.750
9.29
14000.00
12000.00
Modulus of Rupture (psi)
Label
16000.00
y = 25899x - 3970.5
R² = 0.2289
10000.00
8000.00
6000.00
4000.00
2000.00
0.524
0.00
0.000
0.100
0.200
0.300
0.400
Specific Gravity
0.452
0.500
0.600
0.700
Vibration to Strength?
MOR vs. Dynamic MOE
16000.00
14000.00
y = 0.0093x - 6374
R² = 0.2303
12000.00
10000.00
8000.00
6000.00
4000.00
2000.00
0.00
0
500000
1000000
1500000
2000000
2500000
Stiffness to Strength?
MOR vs. Static MOE
16000.00
14000.00
y = 0.024x - 5597.4
R² = 0.8444
12000.00
Modulus of Rupture (psi)
Fresh sawn
MSR lumber
MOR vs MOE
R2 = 0.79 flat
R2 = 0.69 edge
10000.00
8000.00
5% Exclusion Limit
6000.00
4000.00
2000.00
•
Reference: Bodig
and Jayne
0.00
0
100000 200000 300000 400000 500000 600000 700000 800000 900000 1000000
Static MOE (psi)
Conclusions
• Warning - Sample size small and not necessarily
representative
• Static MOE vs. MOR gave best results for NDT
methods sampled
• Variability in sample of deconstruction lumber no
worse than variability in machine stress rated
fresh sawn lumber
• This does not mean that the deconstruction
lumber is stronger or weaker than fresh sawn
(modern) lumber!