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Repairing Concrete Bridge Girders and Guardrails with Carbon Fiber Reinforced Polymers (CFRP) after a Second Impact Event


Repairing impact-damaged concrete structures, including bridge railings, deck edges at bridge railings, and girders, is a persistent challenge facing Departments of Transportation (DOTs) which is expected only to get worse as vehicles get large to accommodate large payloads. Several different repair techniques have been developed to repair impact damage which includes removing and replacing damaged concrete, splicing ruptured prestressing strands, re-establishing internal reinforcement, external post-tensioning, and installation of externally bonded (EB) or near surface mounted (NSM) carbon fiber reinforcements. The type of repair system, or the ability to repair an impact damaged structure at all, depends on many factors including the location, extent, and severity of the damage, the site conditions, the importance and age of the structure and the cost effectiveness of the repair compared to replacement. While these interventions must be considered on a case-by-case basis, there is a growing body of research (and field implementation) that can be used to guide the design and installation of these repairs. Structures that have been impacted once are often located in places where it is likely that they may be re-impacted, especially in congested urban areas. In the event of a second impact event after an initial repair, there is very little information available to provide guidance to bridge engineers on how to assess, design, and install a second repair system. Relevant questions include:

  • How can the extent of the damage (some of which may be concealed by previous repairs) be identified?

  • Should material from previous repairs be removed prior to a subsequent repair? If so, how should it be removed without further damaging the substrate and to what extent (how far from the second impact location) should it be removed?

  • If a carbon fiber reinforced polymer (CFRP)-based solution is selected for a subsequent repair, how well will it bond to the existing composite material?

  • How much capacity can be regained from a second repair after a second impact event?


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 guardrails that have been subjected to a second (or subsequent) impact event,

ii) Develop techniques to assess the extent and of damage in repaired structures after a subsequent impact event,

iii) Develop guidelines for how to implement CFRP-based repairs after a second impact event,

iv) Develop tools to predict the capacity of deck edges/curbs/parapets under post and beam railings, parapet railings, and both reinforced and prestressed concrete girders after a second (or subsequent) impact and repair with CFRP materials, and

v) Compare performance (resistance, concrete containment, etc.) of CFRP-based repairs to subsequent impact loading with traditional repair methods.

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.


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 Sub-Committee on Bridges and Structures, T-6 (Fiber Reinforced Polymer Composites), T-7 (Guardrail and Bridge Rail) and T-10 (Concrete Design) 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.


Impact damage is an ongoing challenge facing state DOTs. The instances of repaired girders, bridge railings and their supporting elements 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, hazardous work zones, and prolonged closures.

Sponsoring Committee:AKB10, Innovative Highway Structures and Appurtenances
Research Period:Longer than 36 months
Research Priority:High
RNS Developer:Dr. Mina Dawood (mmdawood@uh.edu); Dr. Wael Zatar (zatar@marshall.edu); John Holt, P.E. (john.holt@hdrinc.com)
Source Info:Harries, K.A., Kasan, J., Miller, R., and Brinkman, R. (2012). Updated Research for Collision Damage and Repair of Prestressed Concrete Beams: Final Report.

Kim, Y.J., Green, M.F., and Fallis, G.J. (2008a). Repair of bridge girder damaged by impact loads with prestressed CFRP sheets. ASCE Journal of Bridge Engineering 13(1), 15-23.

Kim, Y.J., Green, M.F., and Wight, R.G. (2008b). Live load distributions on an impact-damaged prestressed concrete girder bridge repaired using prestressed CFRP sheets. ASCE Journal of Bridge Engineering 13(2), 202-210.

Miller, A.D. (2006). Repair of Impact-Damaged Prestressed Concrete Bridge Girders Using Carbon Fiber Reinforced Polymer (CFRP) Materials. Master’s Thesis, North Carolina State University, Raleigh, NC.
Date Posted:03/18/2017
Date Modified:03/20/2017
Index Terms:Reinforced concrete bridges, Girders, Guardrails, Repairing, Carbon fibers, Fiber reinforced polymers, Impact, Loss and damage,
Cosponsoring Committees: 
Maintenance and Preservation
Bridges and other structures

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