United States Department of Transportation
i
Impact of overweight vehicles (with heavy axle loads) on bridge deck deterioration.
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2012-03-01
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Abstract:Bridge deck slabs develop compressive stresses from global flexural deformation and locally from high-level
wheel loads when it is subjected to overweight trucks. This study quantified the impact of overweight vehicles
with heavy axle loads on bridge decks using laboratory tests and numerical simulations.
The laboratory tests focused on evaluating the impact of combined mechanical stresses and freeze-thaw cycles on
the durability of air-entrained concrete. Concrete cylinders, after being cured in saturated limewater for 28 days,
were subjected to various levels of compressive loads and then exposed to 300 freeze-thaw (F/T) cycles. Rapid
chloride ion penetrability tests were conducted to evaluate the chloride permeability of the concrete samples. The
laboratory test results indicated that the mechanical loading combined with freeze-thaw cycles significantly
increased the permeability of air-entrained concrete and may accelerate the deterioration of concrete elements
such as bridge decks. The observed permeability increase was due to the fact that higher compressive loads
caused more extensive microcracks in concrete, and the damaged concrete further degrades under freeze-thaw
cycles, which may have further opened and interconnected the microcracks.
Bridge deck analyses were conducted to investigate stress distributions and stress levels in typical concrete
bridge decks subjected to high axle loads. The numerical analyses using the idealized bridge models indicated
that the normal stress in bridge decks in the transverse direction can be significantly affected by the thickness of
bridge deck, the girder spacing, and the magnitude of the wheel loads. The analyses results also indicated that
the normal stresses in the longitudinal direction may be calculated as the summation of the stresses due to global
bending of the bridge superstructure under the truck loads, which can estimated using typical design/rating
procedures and the stress elevations near the wheel loads. The proposed equations may be used, in addition to the
typical design/rating calculations, to capture the adverse stresses in bridge decks subjected to overweight trucks.
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