The Residual Strength ofFire Damaged Dimensional

Lumber

Direct Non-Destructive In-Situ

Brian KukayAnthony Laslovich

Charles Todd

BackgroundBackground……..

1.1. Practical Approach to Practical Approach to Assessing Fire Damage Assessing Fire Damage

2. Contained Fires, 2. Contained Fires, Varying Degrees of Degradation

3. Quantify Change in Residual Flexural Properties

In accordance with the N. A. H. B. :In accordance with the N. A. H. B. :1.1. Removal of small samples for mechanical Removal of small samples for mechanical

testingtesting2.2. Screw Withdrawal TestsScrew Withdrawal Tests3. Chemical Analysis4. Spectral Analysis5. Proof Loading

IntroductionIntroduction……. .

In accordance with the N. A. H. B. :In accordance with the N. A. H. B. :1.1. Removal of small samples for mechanical Removal of small samples for mechanical

testingtesting2.2. Screw Withdrawal TestsScrew Withdrawal Tests3. Chemical Analysis4. Spectral Analysis5. Proof Loading

IntroductionIntroduction……. .

In accordance with the N. A. H. B. :In accordance with the N. A. H. B. :1. Removal of small samples for mechanical

testing2. Screw Withdrawal Tests3. Chemical Analysis4. Spectral Analysis5. Proof Loading

IntroductionIntroduction……. .

In accordance with the N. A. H. B. :In accordance with the N. A. H. B. :1. Removal of small samples for mechanical

testing2. Screw Withdrawal Tests3. Chemical Analysis4. Spectral Analysis5. Proof Loading

IntroductionIntroduction……. .

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

Introduction……..

MaterialsMaterials……. .

MaterialsMaterials……. .

M.S.R.L.M.S.R.L.2400 fb2400 fb2E6 E2E6 E

ProcedureProcedure……. .

ProcedureProcedure……. .

FireFire--Damage Designated GroupsDamage Designated Groups

Timber vs. Dimensional Lumber BehaviorChar RateCore TempReduced Cross Section

FireFire--Damage Designated GroupsDamage Designated Groups

FireFire--Damage Designated GroupsDamage Designated Groups

1.1. LogLog2. Fire-

Damage3. Re-log4. Test

FireFire--Damage Designated GroupsDamage Designated Groups

ProcedureProcedure……. .

ProcedureProcedure……. .

ResultsResults……. .

ResultsResults……. .

Results….

Results predicting EResults predicting EfDfD……. .

Results predicting EResults predicting EfDfD……. .

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%

Results predicting EResults predicting EfDfD……. .

Results predicting MORResults predicting MORDD……. .

Results predicting MORResults predicting MORDD……. .

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)

Results predicting MORResults predicting MORDD……. .

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%

Results predicting MORResults predicting MORDD……. .

Conclusions….

The mean EfD and MOR from are 1,333,215 psi and 5,840 psi.

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

Thank You….Special Thanks to:Special Thanks to:

National Forest Products LaboratoryNational Forest Products LaboratoryNational Committee on Timber BridgesNational Committee on Timber Bridges