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SNAP-TITE
Composite Column Reinforcement
The Need
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Recent earthquakes throughout the
world have demonstrated the vulnerabilities of older reinforced concrete columns to
seismic deformation demands. During earthquakes, seismic forces cause concrete to crack
and expand. Steel rings inside the column must resist these forces, but have failed during
recent earthquakes. These reinforced concrete columns with substandard reinforcement
details and major corrosion problems must be strengthened. Previous technology consisted of concrete or steel jackets. Although
effective, these techniques are costly, time consuming, and require their own maintenance
as well. Following major earthquake damage to bridges and overpasses in 1989, the
California Department of Transportation identified 1,039 bridges that were in need of
seismic retrofitting to prevent spalling and catastrophic failure during earthquakes.
After the 1994 Northridge earthquake, another 1,325 bridges were added to the list. The
need for a more cost effective and user friendly system was imminent.
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The Technology
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The Snap Tite Composite Column
Reinforcement strengthens a concrete column by confining it in an external composite
jacket, which prevents the concrete from expanding during seismic activity or prolonged
freeze-thaw cycles. The pre-manufactured fiberglass jacket is comprised of glass fibers
and corrosion resistant isopolyester resins. The resin completely encapsulates the
reinforcing fiber network, which, for most applications, is conventional E-glass woven
roving and bi-directional fabric. Each Snap Tite component is a single-seamed, cylindrical
jacket that "snaps on" the column. The column is cleaned and prepared with a
high performance urethane adhesive before the first jacket is applied. More jackets are
applied until the desired thickness for the job is achieved. Adhesive is applied between
layers, and the vertical and horizontal jacket seams are symmetrically alternated. A
typical column will require 3 to 4 layers of jackets, with a nominal jacket thickness of
around 1/8 inch thick. Each nested jacket is bound with belt clamps until the adhesive
cures.
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The Benefits
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Snap Tite is recognized as one of
the most cost effective and user friendly solutions for rehabilitating or upgrading
existing steel reinforced concrete columns or structures. Snap Tite replaces steel, the
conventional material used for column reinforcement, reducing installation and long-term
maintenance costs. For example, Snap Tite, because of its light weight, can typically be
installed in three hours vs. three days for steel, and can be lifted in place by workers
using only a few pieces of light, mobile equipment. Snap Tite won't rust and never needs
to be painted, even when installed in corrosive environments. The other market challenge to Snap Tite is the epoxy resin composite column
wrap. Although this composite does meet performance requirements, it is much more
expensive to manufacture. The current manufacturer of this resin also uses extensive
equipment for installation, Snap Tite does not.
Full-scale tests at two major universities have verified that
columns reinforced with Snap Tite withstand three-to-eight times the deflection of columns
without reinforcements. Preliminary tests indicate that Snap Tite can improve earthquake
capability three times beyond that of a steel jacket. |
Status
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Snap Tite has been tested and approved by the
California Department of Transportation to retrofit 3,480 steel reinforced columns on the
Yolo Causeway in northern California. It was the natural choice for this project because
the columns are submerged under water for several months each year. The technology is also
being evaluated to rehabilitate other structures such as wooden utility poles, wooden pier
pilings, and parking structures. This technology was honored as one of 1999 Nova Award Finalists by Construction Industry Forum. |
Barriers
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The column to be retrofitted must be even and
uniform to ensure a good fit with the fiberglass jacket, and to realize the structural
improvements of the process. |
Points of Contact
- Norman C. Fawley, President, NCF Industries, Inc. 2320 Cherry
Industrial Circle, Long Beach, CA 90805-4417. Phone: (562) 602-0400. Fax: (562) 602-0050. Email:ncflbca@aol.com
- Clinton C. Myers, CC Myers,
Inc., Rancho Cordova, CA
- Yan Xiao, Assistant Professor, Department of Civil
Engineering, University of Southern California, 3620 S. Vermont Ave., KAP210, Los Angeles,
CA 90089-2531. Phone: (213) 740-6130. Fax: 744-1426; E-mail:yanxiao@rcf.usc.edu
References
- 1999 Nova Award Nomination Entry, "SNAP TITE Composite
Column Reinforcement.
- "University of Southern California Chronicle, "A
Quick Fix to Make Freeways Quake-Safe", February 6, 1995. http://www.usc.edu/uscnews/stories/1020.html
- Amoco Chemicals Winter 97 Report. "Concrete Columns to
Get Isopolyester Protection."
Disclaimer Statement
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Neither the Construction
Industry Institute nor Purdue University in any way endorses this
technology or represents
that the information presented can be relied upon without further investigation. |
DB, AA
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