This document discusses methods for assessing the residual strength of fire-damaged dimensional lumber through non-destructive in-situ testing. It outlines procedures for containing test fires to achieve varying degrees of degradation, quantifying the change in flexural properties through proof loading and mechanical testing, and developing models to predict elastic modulus and modulus of rupture based on measurements of char rate, cross-sectional area, and proof loading results. Statistically significant models were obtained for predicting elastic modulus and modulus of rupture from non-destructive proof loading tests, allowing direct quantification of changes in flexural properties for members remaining in service after a fire.

1. The Residual Strength of
Fire Damaged Dimensional
Lumber
Direct Non-Destructive In-Situ
Brian Kukay
Anthony Laslovich
Charles Todd

2. Background….
1. Practical Approach to
Assessing Fire Damage
2. Contained Fires, Varying
Degrees of Degradation
3. Quantify Change in Residual
Flexural Properties

3. Introduction….
In accordance with the N. A. H. B. :
1. Removal of small samples for mechanical
testing
2. Screw Withdrawal Tests
3. Chemical Analysis
4. Spectral Analysis
5. Proof Loading

4. Introduction….
In accordance with the N. A. H. B. :
1. Removal of small samples for mechanical
testing
2. Screw Withdrawal Tests
3. Chemical Analysis
4. Spectral Analysis
5. Proof Loading

5. Introduction….
In accordance with the N. A. H. B. :
1. Removal of small samples for mechanical
testing
2. Screw Withdrawal Tests
3. Chemical Analysis
4. Spectral Analysis
5. Proof Loading

6. Introduction….
In accordance with the N. A. H. B. :
1. Removal of small samples for mechanical
testing
2. Screw Withdrawal Tests
3. Chemical Analysis
4. Spectral Analysis
5. Proof Loading

7. Introduction….
“…Proof loading may be used,
which will permit the non-
destructive determination of
individual members without
testing the total sample to
destruction (ASTM D 4761-05).”

8. Materials….

9. Materials….
M.S.R.L.
2400 fb
2E6 E

10. Procedure….

11. Procedure….

12. Fire-Damage Designated Groups

13. Fire-Damage Designated Groups
Timber vs. Dimensional Lumber Behavior
Char Rate
Core Temp
Reduced Cross Section

14. Fire-Damage Designated Groups

15. Fire-Damage Designated Groups
1. Log
2. Fire-
Damage
3. Re-log
4. Test

16. Procedure….

17. Procedure….

18. Results….

19. Results….

20. Results….

21. Results predicting EfD….

22. Results predicting EfD….

23. Results predicting EfD….
EfD = – 3243439 + 655810 (A2) + 633237 (Ad) + 0.88672 (EfPLND)
P-values (0.0113) (0.0083) (<0.0001)
Example:
EfD = – 3243439 + 655810 (4.32 in2) + 633237 (0.38 in2) + 0.88672 (1,841912 psi) = 1,462,721 psi
Measured: 1,450,801 psi
Results Differ by 1%

24. Results predicting MORD….

25. Results predicting MORD….

26. Results predicting MORD….
MORD = – 2823.50 – 8031.57 (A2) + 10043 (I2) – 35056 (SGD)
P-values (0.1901) (0.0938) (0.0149)
– 599.43 (SOG) + 0.00417(EfPLND)
(0.1354) (0.0003)

27. Results predicting MORD….
Example:
MORD = – 2823.50 – 8031.57 (4.32 in.) + 10043 (3.80 in4) – 35056 (.08)
– 599.43 (1.19) + 0.00417 (1,841,912 psi)
= 4,806 psi
Measured = 4,448 psi
Results Differ by 7%

28. Conclusions….
Statistically significant results obtained for:
EfD via proof loading
MOR via proof loading
Cold strength/stiffness values approximate
fire damaged specimen w/ additional 7/16 in depth-
wise reduction beyond reduced dimension.
Post-fire investigators directly quantifying Δ flexural
properties of members expected to remain in service
The mean EfD and MOR from are 1,333,215 psi and 5,840 psi.

29. Thank You….
Special Thanks to:
National Forest Products Laboratory
National Committee on Timber Bridges