Repairing and Strengthening Concrete Bridge Girders and Railings with Carbon Fiber Reinforced Polymers (CFRP) For Impact Damage
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Description: | Repaired regions of impact-damaged concrete girders with
installation of externally bonded (EB) or near surface mounted (NSM) carbon
fiber reinforcements has been observed to improve structural resistance to
subsequent impact events. This evidence led the Texas Department of
Transportation to replace its standard prestressed concrete girder impact protection
detail, a structural steel angle bolted to the bottom girder flange edge, with
a detail that uses a CFRP wrap of the bottom flange over the travel lanes. These observations and implementation of CFRP
to “harden” a concrete structural element for impact damage by a DOT leads to
the question will this approach benefit DOTs with their concrete traffic
railing, especially those railings that require frequent repair, such as on
highly curved ramps. Research is needed to evaluate the performance of prestressed
and reinforced concrete elements such as girder flanges/webs and concrete
traffic barriers and to determine if the performance under impact improved with
the application of CFRP wrapping.
DOTs have invested in developing techniques for repairing impact-damaged
concrete structures. Given the susceptibility for structures at some sites to
be re-impacted after being repaired, developing guidelines for repairs after
initial impacts is an important task to help maintain the integrity and safety
of the transportation system. If CFRP wrapping can improve the impact
performance of concrete elements such as girders and concrete railings, for both new installations and maintenance
repairs, this can benefit DOTs with their maintenance program and the safety of
workers and the traveling public.
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Objective: | The objectives of the proposed research are to:
i) Identify when it
is appropriate to adopt a CFRP-based system to repair concrete girders and railings
subject to multiple impact events,
ii) Develop techniques
to assess the extent of damage in repaired structures after a subsequent impact
event,
iii) Develop guidelines
for how to implement CFRP-based strengthening and/or repairs for impact events
based on results from full-scale dynamic impact testing,
iv) Develop tools to
predict the capacity of prestressed concrete girders and railings for initial
and second (or subsequent) impacts and repair.
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Benefits: | Impact damage to concrete girders and railings is an ongoing
challenge facing state DOTs. The instances of repaired girders and railings
being re-impacted are common. The lack
of a comprehensive set of guidelines for repair after second impacts limits the
ability of DOTs to implement effective solutions and will typically require
extensive research in the event a second repair is needed. The availability of
comprehensive guidelines for these repairs will help extend the life of the
existing infrastructure system and reduce the need for costly emergency
replacements and prolonged closures.
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Related Research: | NCHRP has sponsored a synthesis study to assess the state of
the art in repairing impact-damaged prestressed concrete bridge girders through
NCHRP Project 20-07, Task 307 (Harries et al., 2012). In that study different
repair systems were identified and assessed, and guidelines were provided on
when to repair impact damaged elements and when to replace them. The North
Carolina Department of Transportation (NCDOT) sponsored research to investigate
the use of un-stressed externally bonded CFRP for flexural and shear repair of
impact damaged AASHTO girders (Miller, 2006). The use of prestress externally
bonded CFRP to repair impact damaged prestressed girders was demonstrated
through a field application in Canada (Kim et al., 2008a). In a subsequent study a numerical model was
developed to determine the live load distribution factors of the repair bridge
(Kim et al., 2008b). While representing only a small subset of the existing
literature, these studies demonstrate that the use of CFRP to repair
impact-damaged girders can effectively restore the capacity of the elements to
their original state. While the NCHRP study identified some structures which
have been repaired multiple times using FRP composites, no comprehensive study
or guidelines have been identified to facilitate the regular use of this repair
approach.
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Implementation: | Formal adoption of guidelines through AASHTO is anticipated
as the primary outcome of the proposed research. To that end, it is expected
that approval through AASHTO would be pursued and that that AASHTO Committee on
Bridges and Structures, T-6 (Fiber Reinforced Polymer Composites), T-10
(Concrete Design), and T-7 (Bridge Railing) would play key roles in the
development and approval of such a document. The availability of such an AASHTO
guideline would facilitate implementation by state DOTs. Given the
unpredictable nature of impacts and collisions, it is not possible to predict
how soon after completion of the research implementation of these guidelines
could be expected. The report on NCHRP Project 20-07, Task 307 (Harries et al.,
2012) indicates that repairs of second impacts have been implemented by some
DOTs. Implementation on a demonstration basis is anticipated as the first step
towards broader implementation until confidence in the approach is gained.
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Sponsoring Committee: | AKB10, Innovative Highway Structures and Appurtenances |
Research Period: | Longer than 36 months |
Research Priority: | High |
RNS Developer: | Taya Retterer, P.E. Texas Department of Transportation, Bridge Division |
Source Info: | Taya Retterer, P.E. - Texas Department of Transportation, Bridge Division Wael Zatar, Ph.D. - Marshall University John Holt, P.E., F.SEI - Modjeski and Masters, Inc. |
Date Posted: | 06/28/2021 |
Date Modified: | 07/09/2021 |
Index Terms: | Repairing, Strengthening (Maintenance), Concrete bridges, Girders, Bridge railings, Carbon fibers, Fiber reinforced polymers, Impact, |
Cosponsoring Committees: | |
Subjects |
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Construction
Maintenance and Preservation
Materials
Bridges and other structures
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