Recommended Guide Specification for the Design of Externally Bonded FRP Systems for Repair and Strengthening of Concrete Bridge Elements (2010) / Chapter Skim
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The concept of using externally bonded FRP reinforcement to strengthen concrete structures was developed as an improvement to the use of externally bonded steel plates. Strengthening with externally bonded steel plates commenced in 1964 in Durban, South Africa, to address the problem of the accidental omission of steel reinforcing bars of a basement beam in an apartment complex (Dussek 1980)
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From page 5... ...
The criteria for checking safety and serviceability of structural members and components that have been strengthened with externally bonded FRP reinforcement are based on a target reliability index, β, of 3.5 (the target value assumed in the development of the AASHTO LRFD Bridge Design Specification)
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From page 6... ...
This load combination consists of the three components of dead load, static live load, and dynamic load: The mean, μQ, and variance, σ 2Q, of Q are: where μDL1 and σDL1 = mean and standard deviation of the dead load due to factory made (precast) elements, μDL2 and σDL2 = mean and standard deviation of the dead load due to cast in place concrete, μDL3 and σDL3 = mean and standard deviation of the dead load due to miscellaneous nonstructural components, and μLL+IL and σLL+IL = mean and standard deviation of the live load with impact.
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From page 7... ...
The mean compressive strength of concrete reflects the difference between standard-cured and in situ conditions, and includes an allowance for aging. For FRP reinforcement, the strength depends on the engineering characteristics of the fibers, matrix and adhesive systems and on the workmanship in fabrication and installation.
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From page 8... ...
An advantage of the shop-manufactured composites over the field-manufactured composites is the ability to control the quality and uniformity in the composite reinforcing systems. Conversely, field-manufactured composites are better able to conform to non-uniform concrete surfaces.
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From page 9... ...
2.3.3.3 Resistance A summary of the resistance statistics for typical reinforced concrete bridge girders without externally bonded FRP reinforcement is presented in Table 2.4, where the components of the statistics of the parameters in Equation 2.11 are also presented. These statistics were determined from previously published assessments of statistics in resistance of reinforced concrete structures (MacGregor et al.
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From page 10... ...
The reliability assessments in subsequent sections of this paper are performed by simulation. 2.4.3 Selection of the Target Reliability Indices The target reliability benchmarks for bridge structural members and components strengthened with externally bonded FRP reinforcement were selected through a comprehensive evaluation of selected representative bridge elements that were judged to be candidates for repair and/or strengthening.
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From page 11... ...
, φfrp = resistance factor determined from reliability analysis, and k2 = multiplier for locating resultant of the compression force in the concrete. For shear: Where Vc = the nominal shear strength provided by the concrete in accordance with Article 5.8.3.3 of the AASHTO LRFD Bridge Design Specifications, Vs = the nominal shear strength provided by the transverse steel reinforcement in accordance with Article 5.8.3.3 of the AASHTO LRFD Bridge Design Specifications, Vp = component of the effective prestressing force in the direction of applied shear as specified in Article 5.8.3.3 of the AASHTO LRFD Bridge Design Specifications, Vfrp = the nominal shear strength provided by the externally bonded FRP reinforcement, φ = 0.9, and φfrp = resistance factor determined from reliability analysis.
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