1. Influence of Creep on the Stability of
Pultruded E-Glass / Polyester Composite
Columns at Elevated Service Temperatures
By: Evan A. Bennett
Advisor: David W. Scott, Ph. D.

2. FRP in Civil Engineering
FRP Components in Civil Engineering
No Reliable Design Criteria
Long-Term Behavior
Elevated Temperatures
Goals of the Current Work
Expand on Previous Creep Studies on FRP
Components
Develop Semi-empirical Predictive Equations for
Lateral Creep Displacement
Better Understanding of Long-Term Behavior
Examine Impact of Elevated Temperatures

3. Short-Term Properties
Test Specimens 4
Pultruded 4 x 4 x ¼”
Square Tubes
6 ft Length
4
Extren Series 500 1/4
Isophthalic Polyester
Resin
E-Glass Rovings and
CSM

4. Buckling Loads
π 2 EL I
C
PE
PE = Pe =
1 + (ns PE Ag GLT )
2
(1) (2)
Leff
Short-Term Critical Load Approximations
Approximation
Current Study Butz Euler Modified Euler
(Experimental) (Experimental) (Equation 1) (Equation 2)
Pcr
50.5 46.6 53.5 49.9
(kips)

5. Testing Apparatus
Top Plate
Knife Edge
Typical Creep Frame
(Room Temp. Tests)
L eff = 75 in
1-1/2" Threaded Rod
1-1/2" Hexagonal Nut
Middle Plate
20 x 20 x 1" Steel Spring
Plate
Bottom Plate
Hydraulic Jack
Load Cell
FRONT VIEW

6. Testing Apparatus

7. Elevated Temperature Chambers

8. Manufacturers Recommendations
From Strongwell Corporation Extren Design Manual (2002)
F.O.S. = 3

9. Long-Term Testing
Creep Test Matrix
Temperature Duration
Specimen l (P/Pcr)
(°F) (hours)
PG-33-R 0.33 73 1000
PG-33-E 0.33 150 1000
PG-67-R 0.67 73 1000
PG-67-E 0.67 150 1000
PG-90-R 0.90 73 1000
PG-90-E 0.90 150 1000

10. Long-Term Results
Midheight Lateral Deflection of All Specimens
0.14
PG-33-R
PG-33-E
PG-67-R 0.12
3
PG-67-E
PG-90-R
PG-90-E
0.10
2 0.08
d (mm)
d (in)
0.06
1 0.04
0.02
0 0.00
0 200 400 600 800 1000 1200
Time (hours)

11. Quasielastic Method
Schapery (1965)
Vinogradov (1987)
Kang (2001)
Remove Eccentricity from Kang’s Analysis
λ tn
δ = Ai (3) ψ (t ) = (4)
1− λ β
λ [1 +ψ (t )]
δ (t ) = Ai (5)
1 − λ [1 +ψ (t )]

12. Determination of Quasielastic Parameters
3.0 Room Temperature 0.12
Specimens
2.5 0.10
PG-33-R
PG-67-R
PG-90-R
2.0 0.08
PG-33-R Prediction
PG-67-R Prediction
d (mm)
d (in)
PG-90-R Prediction
1.5 0.06
1.0 0.04
0.5 0.02
0.0 0.00
0 200 400 600 800 1000 1200
Time (hours)

13. Determination of Quasielastic Parameters
0.14
Elevated Temperature
Specimens 0.12
3
0.10
2 0.08
d (mm)
PG-33-E
d (in)
PG-67-E
PG-90-E
PG-33-E Prediction 0.06
PG-67-E Prediction
PG-90-E Prediction
1 0.04
0.02
0 0.00
0 200 400 600 800 1000 1200
Time (hours)

14. Findley’s Power Law
1
10 PG-90-R
ε (t ) = ε 0 + mt n (6)
0.1
1
d (mm)
m
d (in)
0.01
n
δ (t ) = δ 0 + mt n
0.1
(7)
0.001
0.01
0.0001
1 10 100 1000 10000
Time (hours)
log[δ (t ) − δ 0 ] = log(m ) + n log(t ) (8)

15. Inclusion of Temperature Effects in Predictive Model
Findley et al. (1956)
⎛σ ⎞ ⎛σ ⎞
ε (t ) = ε '0 sinh⎜
⎜σ ⎟ + m' t n sinh⎜
⎟ ⎜σ ⎟
⎟ (9)
⎝ ε ⎠ ⎝ m⎠
Applied to Lateral Deflection
⎛ λ ⎞
δ (t ) − δ 0 = m' t sinh⎜ ⎟
n
⎜λ ⎟
(10)
⎝ m⎠
Including Temperature
⎛ λ ⎞
δ (t ,τ ) − δ 0 = τm' t sinh⎜ ⎟ (11)
T
n
⎜λ ⎟ τ = (12)
⎝ m⎠ TR

16. Findley Predictions of Lateral Creep
0.14
Room Temperature
Specimens
3 0.12
PG-33-R
PG-67-R 0.10
PG-90-R
PG-33-R Prediction
PG-67-R Prediction
d (mm)
d (in)
2 0.08
PG-90-R Prediction
0.06
1 0.04
0.02
0 0.00
0 200 400 600 800 1000 1200
Time (hours)

17. Findley Predictions of Lateral Creep
0.14
Elevated Temperature
Specimens 0.12
3
0.10
PG-33-E
PG-67-E
PG-90-E
2 PG-33-E Prediction 0.08
d (mm)
d (in)
PG-67-E Prediction
PG-90-E Prediction
0.06
1 0.04
0.02
0 0.00
0 200 400 600 800 1000 1200
Time (hours)

18. Extended Predictions of Lateral Creep
Deflection
Predicted Lateral Deflection (in)
Specimen 1000
1 Year 5 Years 10 Years 25 Years
Hours
PG-33-R 0.004 0.007 0.010 0.012 0.015
PG-33-E 0.008 0.014 0.021 0.025 0.031
PG-67-R 0.013 0.022 0.032 0.038 0.048
PG-67-E 0.026 0.045 0.066 0.078 0.098
PG-90-R 0.027 0.046 0.068 0.080 0.100
*PG-90-E 0.127 -7.694 -0.288 -0.219 -0.174
*Predicted using Quasielastic Creep Parameters

19. Post-Creep Buckling Tests
d (in)
Recovery 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
60
1 Week (168 Hours) 250 PG-33-E
Permanent Modulus 50
Reduction 200
π 2 EL I
C 40
PE =
Load (kips)
50
Load (kN)
2 150
Leff 40 30
d (mm)
30
100
Specimen Failure 20 Slope = 227 kN (50.9 kips) 20
10
50
0 10
0.00 0.05 0.10 0.15 0.20 0.25
d/P (mm/kN)
0 0
0 10 20 30 40
d (mm)

20. Specimen Failure

21. Post-Creep Buckling Test Results
Experimental Buckling Loads
Pexp Pexp /PE Pexp /PST
Specimen
(kips) (%) (%)
PG-33-R 50.5 94.4 99.9
PG-33-E 50.9 95.3 100.8
PG-67-R 50.5 94.4 99.9
PG-67-E 34.1 63.7 67.5
PG-90-R 59.2 110.7 117.2
PG-90-E 32.5 60.7 64.4
PE (kips) 53.5 PST (kips) 50.5

22. Conclusions
Quasielastic Method Effective with Bending
Power Law Model Effective without Bending
Transition Point Between l = 0.67 and l = 0.90
Sustained Loads and Elevated Temperatures
Reduce Modulus
F.S. = 3 Appears Reasonable