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Pages 7-18

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From page 7...
... 7   Research Approach 2.1 Introduction e purpose of the research was to determine the best methodology to prevent cracking of shear keys in adjacent box girder bridges. e research portion of this project had three distinct phases: literature review, analytical modeling, and full-scale testing.
From page 8...
... 8 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Variable Effectiveness at preventing leakage Effectiveness at load transfer Comments Shear Key Shape Traditional, top, partial depth Ineffective Varies with material Evidence shows this configuration is subject to very high stress due to thermal movements and possible lateral (plate) bending of the system.
From page 9...
... Research Approach 9 Variable Effectiveness at preventing leakage Effectiveness at load transfer Comments Load Transfer Mechanisms Other Than Shear Keys Untensioned transverse bars Ineffective Effective Evidence suggests that lateral tie bars, tensioned or untensioned, will transfer load between adjacent box girders. Untensioned bars provide no cracking or leakage benefit.
From page 10...
... 10 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems 2.3 Analytical Modeling Aer completing the literature review, the research team proposed several analytical models to assess the shear key performance. e purpose of the analytical modeling was: 1.
From page 11...
... Research Approach 11 models were various congurations of spans, girder depths, shear key types and decks with lateral post-tensioning. e nal four models had reinforced shear keys.
From page 12...
... 12 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems Standard Type III Concrete None Standard Type III Concrete None Thin Full-Depth Type IV Concrete None Thin Full-Depth Type IV Concrete None Thin Full-Depth Type IV Concrete None Thin Full-Depth Type IV Concrete None Thick Full-Depth Type V Concrete None Thick Full-Depth Type V Concrete None Thick Full-Depth Type V Concrete None Thick Full-Depth Type V Concrete None Mid-Depth Concrete None Mid-Depth Concrete None Mid-Depth Concrete None Mid-Depth Concrete None Standard Type III Asphalt None Thin Full-Depth Type IV Asphalt None Thick Full-Depth Type V Asphalt None Mid-Depth Asphalt None Standard Type III Concrete None Thin Full-Depth Type IV Concrete None Thick Full-Depth Type V Concrete None Mid-Depth Concrete None Standard Type III Concrete None Thin Full-Depth Type IV Concrete None Thick Full-Depth Type V Concrete None Mid-Depth Concrete None Standard (Type III) Concrete Ends/Midspan Standard (Type III)
From page 13...
... Research Approach 13 2.4 Full-Scale Testing of the System Full-scale testing had two components: 1. A full-scale bridge section consisting of three girders and two shear key joints was constructed in the laboratory.
From page 14...
... 14 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems concern about being able to mix large quantities of grout quickly enough. e Type V shear key was lled with concrete.
From page 15...
... Research Approach 15 rough sandpaper. A CSP of 9 has a roughness of about ¼ inch.
From page 16...
... 16 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems The sequence of testing was: 1. The girders were heated and cooled several times prior to casting the shear keys to establish thermal properties.
From page 17...
... Research Approach 17 c. Small aggregate concrete.
From page 18...
... 18 Guidelines for Adjacent Precast Concrete Box Beam Bridge Systems 5. The following was recorded: a.

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