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The National Academies

NCHRP 20-07/Task 107 [Completed]

Shear Design Guidelines for Skewed Multi-Beam Bridges
[ NCHRP 20-07 (Research for AASHTO Standing Committee on Highways) ]

  Project Data
Funds: 74410
Research Agency: Modjeski & Masters
Effective Date: 7/1/1999
Completion Date: 12/31/2001
Comments: Completed

Task 107, FY 1999, "Shear Design Guidelines for Skewed Multi-Beam Bridges" (Modjeski & Masters, Inc., John Kulicki). Article 4.6.2.2.3C, Skewed Bridges, in the AASHTO LRFD Bridge Design Specifications requires that shear in the exterior beam at the obtuse corner of the bridge shall be adjusted when the line of support is skewed. The specifications provide correction factors for this adjustment and require that the correction factors be applied to all beams in the cross-section.

In the development of these correction factors, the variation of the effect of skew on the individual beam reactions was not considered. In addition, the specifications provide no guidance on the influence of skew on the shear along the length of the beam. The commentary to the specifications states that the proscribed corrections are conservative. As a consequence of this conservatism, some beams in the bridge are over-designed.

The objective of this study was to develop design guidelines suitable for inclusion in the AASHTO LRFD Bridge Design Specifications for estimating the shear in skewed bridges at the supports and along the length of the beams. The final report can be downloaded HERE. (NCHRP Staff: D.B. Beal)

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