5 frp composites busel
TRANSCRIPT
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Introduction of Fiber Reinforced Polymer
(FRP) Materials
John BuselAmerican Composites Manufacturers Association
January 9, 2007Orlando
Towers, Poles & Conductors Meeting
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• What is FRP ?
• FRP benefits
• Current Status of FRP Utility Structures
• Installations
• FRP performance
• Changes to 2007 NESC code
Outline
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Compared to other
engineering materials
composites have
different properties
What is FRP ?
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Metals - Homogeneous &Isotropic
Composites -Inhomogeneous & Anisotropic
What is FRP ?The Difference Between Composites and Other Materials
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Definition:
Composites are a combination of a reinforcement fiber in a polymer resin matrix, where the reinforcement has an aspect ratio that enables the transfer of loads between fibers, and the fibers are chemically bonded to the resin matrix.
Creates a material with attributes superior to either component alone!
What is FRP ? Fiber Reinforced Polymer (FRP) Composites
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Products made for utility structures are manufactured several ways
• Pultrusion
• Filament Winding
What is FRP ?
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Pultrusion Process
Resin
Heated DieCuredProfile
Bridge decks, rebar, structural profiles, concrete & masonry structural strengthening, sheet piling, dowel bars, utility poles, grating
What is FRP ?
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Filament Winding
Resin
Utility poles, columns, bridge girders, pipe, missiles, aircraft fuselage
What is FRP ?
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• Lightweight – easy to handle and transport
• High Strength to weight ratio
• Corrosion resistant – will not rot or corrode
• Non-conductive (essentially a large hot stick)
• Non-magnetic
• Impervious to pests and woodpecker attack
• Design – Tailor material properties, some systems are modular
• Compatible – use standard hardware
• Environmentally safe – no leaching of toxic chemicals into soil
FRP Benefits
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• FRP utility structures include poles, crossarms, stand-offs and now conductor reinforcement
• Composite, or “fiberglass” poles, were installed in West Oahu in 1962 and were only recently taken out of service
• Composite lighting poles have an extensive history of use dating back more than 40 years
• The use of FRP utility structures throughout the U.S. is widespread and still growing
• The use of FRP utility structures in Canada is growing• Some larger installations...
• 8,000+ FRP poles at large California utilities starting 1995• 1,500+ FRP poles at Rural Coops since 2000• 300+ FRP poles at Northwest Territories since 2003• 100,000+ FRP crossarms across virtually every state
Current Status of FRP Utility Structures
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Installations
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Residential Backyard Installations
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Remote Installations
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Deadend Crossarms
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Joint Use with Transformers
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Claim by Manufacturers…”Since FRP structures are engineered like steel and prestressed concrete, and manufactured, they result in good initial strength consistency” Question: Is this true?
FRP Performance
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Answer: Yes EDM has performed numerous proprietary bending strength tests on FRP utility poles and crossarms for several manufacturers.
Conclusion: the poles and crossarms yielded very consistent (low COV) as manufactured strength properties
FRP Performance
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3,100
3,5003,300
3,0003,150
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
Pole 1 Pole 2 Pole 3 Pole 4 Pole 5
Lo
ad a
t F
ailu
re (
lb)
3,100
3,5003,300
3,0003,150
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
Pole 1 Pole 2 Pole 3 Pole 4 Pole 5
Lo
ad a
t F
ailu
re (
lb)
COV = 6.1 %
Actual 40' Filament Wound Pole Bending Strengths (Tested by EDM)
FRP Performance
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Actual 40' Pultruded Pole Bending Strengths(Tested by Manufacturer)
COV = 3.4%
Load-Deflection very nearly linear
FRP Performance
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The first FRP poles for overhead line application were designed using a net overload factor (“Application Safety Factor”) of 4.0, the same as required for (Grade B) wood construction
Question: What factors are now being employed for FRP Utility Poles and Crossarms?
FRP Performance
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The use of overload factors as applied to FRP utility poles is all over the map
• Some utilities using a factor of 2.5
• Some using 3.0
• Some using 3.85
• Some still using 4.0
FRP Performance
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The use of overload factors as applied to FRP crossarms is more consistent
• Most utilities use a factor of 2.5
FRP Performance
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Cantilever Loading
• Load-deflection curve very nearly linear
• Typical break is due to local stress rupture on the compression face and is most often associated with local buckling
• Kinematics of pole deflection cause loss of cross-section inertia as the pole begins to oval which means EI decreases
• Failure in area where applied stress first exceeds allowable stress
• Typical allowable stresses in the range of 25,000 psi to 45,000 psi
FRP Performance Failure Mechanisms of FRP Poles
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Tangent and Deadend Loading• Load-deflection curve very nearly linear
• Typical break is due to local stress rupture on the compression face and typically propagates from the attachment to the pole
• Crossarm breaks can also be snap breaks, or crushing breaks if crossarm mounted directly to pole without a bracket
• Failure in area where applied stress first exceeds allowable stress
• Typical allowable stresses in the range of 25,000 psi to 45,000 psi.
• FRP crossarms are typically pultruded and perform like pultruded poles
FRP Performance Failure Mechanisms of FRP Crossarms
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• Subcommittee 5: Strength & Loading• Sections 24, 25, 26, 27
• Taskforce 5.1.7: FRP Structures• Change Proposal accepted in 2005
• Reduced Application Safety Factor
• Material Strength Factors same as STEEL provided that FRP pole and crossarm strengths are published as 5% LEL values (5th percentile strength)
Changes to 2007 NESC
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• Added NOTE References
• ASCE-104, Recommended Practice For Fiber-Reinforced Polymer Products For Overhead Utility Line Structures
• ASCE-111, Reliability-Based Design of Utility Pole Structures ….. (provides 5% LEL)
• ASCE/SEI Task Committee – develop FRP Manual of Practice
Changes to 2007 NESC
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Table 253-1 -- Load factors for structures,1 crossarms, support hardware, guys, foundations, and anchors to be used with the strength factors of Table 261-1A
Load Factors
Grade C
Grade B At crossings 6 Elsewhere
Rule 250B Loads Vertical Loads 3
1.50
1.90 5
1.90 5
Transverse Loads Wind Wire Tension
2.50
1.65 2
2.20
1.30 4
1.75
1.30 4
Longitudinal Loads In general At dead-ends
1.10
1.65 2
No requirement
1.30 4
No requirement
1.30 4
Rule 250C Loads 1.00 0.87 7 0.87 7
Rule 250D Loads 1.00 1.00 1.00
........................................... 5 For metal prestressed concrete, or fiber-reinforced polymer portions of structures and crossarms, guys, foundations and anchors, use a value of 1.50.
Changes to 2007 NESC
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Table 261-1AStrength Factors for Structures
Grade B Grade C
Strength factors for use with loads of Rule 250B
Metal and Prestressed-Concrete Structures 6 1.0 1.0
Wood and Reinforced-Concrete Structures 2,4 0.65 0.85
Fiber-Reinforced Polymer Structures 6 1.0 1.0Support Hardware 1.0 1.0
Guy Wire 5,6 0.9 0.9
Guy Anchor and Foundation 6 1.0 1.0
Strength factors for use with loads of Rule 250C
Metal and Prestressed-Concrete Structures 6 1.0 1.0
Wood and Reinforced-Concrete Structures 3,4 0.75 0.75
Fiber-Reinforced Polymer Structures 6 1.0 1.0Support Hardware 1.0 1.0
Guy Wire 5,6 0.9 0.9
Guy Anchor and Foundation 6 1.0 1.0
Changes to 2007 NESC