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Automated Composite Column Wrapping
The Need
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Recent earthquakes in urban areas such as Loma
Prieta ’89, Northridge’94, and Kobe ’95, have repeatedly demonstrated the
vulnerabilities of older reinforced concrete columns to seismic deformation demands.
Particularly vulnerable are reinforced concrete bridge piers that were designed prior to
the lessons learned from the 1971 San Fernando earthquake. These reinforced concrete columns with substandard reinforcement details and
heavy corrosion problems, need to be strengthen using retrofit systems, consisting of
concrete or steel jackets. Although effective, these systems are costly, installation is
time consuming and some maintenance problem may arise.
To increase the speed of installation, reduce maintenance
and improve durability, different types of advanced composite column jacketing systems
have been investigated and developed.
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Corrosion Retrofit
RoboWrapper
Curing Process
RoboWrapper Jr.
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The Technology
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The Automated Composite Column Wrapping is
performed by a patented machine known as Robo-Wrapper. Currently there are three versions
of the machine available for bridge retrofit work depending on the size of the columns
being wrapped. The material used is manufactured by
Thiokol Corporation and is designated "Akso Fortifil 50K/UF3325-90". It is made
of carbon fibers pre-impregnated with epoxy resin under factory controlled conditions.
Once installed on the column the material is cured with an
oven at 310 ยบ F for one hour. The curing process converts the individual tows into a
solid casing which is then coated with a textured paint to match the surrounding
structure.
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The
Benefits
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Composite column retrofit jacket systems can
be structurally just as effective as conventional steel jacketing in improving the seismic
response characteristics of substandard reinforced concrete columns. Composite column retrofit system is less costly (About 10%) than
Steel Jackets. Its installation can be perfumed in less time, and its uniform application
and curing considerably reduces maintenance costs.
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Status
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XXSys Technologies manufactures the equipment
needed to perform the Automated Composite Column Wrapping. Several projects have been done
up to date, most of them in California, where the existence of high seismic risk and old
concrete structure has opened a big market for this concrete column retrofit system. |
Barriers
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Concrete structures with not uniform surface
might need to be treated and fixed before applying the composite wrapping. Since the
process is automatic, uneven surfaces can cause poor quality retrofit. |
Points of Contact
Vice President Engineering. 4619
Viewridge Avenue. San Diego, CA 92123. Phone: (619) 974-8200 Fax: (619) 794-8208
References
- Seible, F. and Karbhari, V "Seismic retrofit for
bridge columns using advanced composite materials" Division of Structural
Engineering. University of California, San Diego. La Jolla, CA 92093-0085
- XXSys Technologies, Inc " Automated Composite Column
Wrapping - Process Overview Manual" October 1997
- Civil Engineering Magazine "Safe Parking during a
quake" August 1997
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. |
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