Fatigue Design Considerations for Reinforcement in Concrete Bridge Decks*


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Title: Fatigue Design Considerations for Reinforcement in Concrete Bridge Decks*

Author(s): Neil M. Hawkins

Publication: Journal Proceedings

Volume: 73

Issue: 2

Appears on pages(s): 104-115

Keywords: bendhq (reinforcing steels);bridge decks;bridges (structures);concrete finishes (hardened concrete);corrsion;crackinq (fracturing);cyclic loads;epoxy resins; exposure;fatigue (materials); fatigue tests;impact;loads (forces);plastics, polymers, and resins.

Date: 2/1/1976

Examines the realism of the 1973 AASHTO limitation on the allowable stress range for reinforcing bars in concrete bridge decks. Data are considered in turn for (I) the vehicle characteristics dictating the dominant stresses in bridge decks, (2) the factors governing the dynamic amplification of those characteristics, (3) prediction of reinforcement stresses caused by given loadings, and (4) fatigue damage characteristics for reinforcing bars, black, corroded, galvanized, epoxy coated, bent, and welded. It is shown to be unrealistic to evaluate the potential fatigue life of a bridge deck by routinely applying the provisions of the 1973 AASHTO bridge standards. For present loadings and reinforcement grades, fatigue will not be a problem unless the reinforcement is corroded, bent, poorly welded, or poorly galvanized. More realistic provisions would limit the stress range caused by moments, evaluated by the AASHTO standards for wheel loads equal to three-eighths of the legal tandem-axle load, to 21 ksi (430 kgf/cm2), for epoxy coated or black bars not exposed to corrosive influences, I9 ksi (I 300 kgf/cm2) for galvanized bars, and 17 ksi (1160 kgf/cm2) for black or galvanized bars exposed to corrosive influences.