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it is mandated for older bridges. This is viewed as more of a pol- · Not be a pure simplification of the existing LRFD
icy issue to ensure consistency, than a technical issue. specifications because a significant shortcoming of
The following states responded to the questionnaire: the current LRFD shear design provisions was
Alaska, Arkansas, California, Delaware, FHWA CFLHD, considered to be the difficulty of fully understanding
Florida, Georgia, Illinois, Kansas, Kentucky, Missis- the MCFT and how the LRFD provisions were
sippi, Missouri, Montana, Nevada, New Hampshire, New derived from this theory.
Jersey, Oregon, Pennsylvania, Tennessee, Texas, and · Avoid the necessity of calculating the angle . If a sim-
Washington. ple relationship is to be suggested for calculating , then
there needs to be a default value that can be used if the
2.5 CRITERIA FOR PROPOSED engineer does not wish to make this calculation;
SIMPLIFIED PROVISIONS · Not enable the effects of all actions (axial load, moment,
shear, and prestressing) to be simultaneously considered
Based on the experiences of practicing engineers, the as this is already done in the current LRFD Sectional
review of shear design methods in codes of practice, Design Model (S5.8.3);
the analysis of experimental test data, and a comparison of · Provide safe and accurate estimates of shear capacity of
the required amounts of shear reinforcement for sections in a the members in the selected experimental test database
design database (presented in Section 2.9), the following set without significant trends in the strength ratios
of criteria were developed for the simplified provisions: (Vtest /Vcode) with design parameters (d, f c, v fy, l, etc).
The simplified provisions should · Result in reasonable shear reinforcement amounts (v fy)
being required for the sections in the design database
· Be directly usable, without iteration, for the design of a where "reasonableness" is assessed from a comparison
member; of the required amounts of shear reinforcement by
· Be directly usable, without iteration, for evaluating the analysis methods in comparison with the requirements
capacity of a member; of other codes of practice and analysis methods.
· Be useful in conducting field evaluations by providing
the engineer with an estimate of the loads at which shear Where the required shear reinforcement amount (v fy) by
cracking is expected to occur in the member; the simplified specifications differs substantially from what
· Have a basis that can be readily understood and is required by the existing AASHTO Standard Specifica-
explained by one engineer to another while still being tions, the LRFD specifications, and analytical methods, then
based on a mechanistic model for strength; the reasons for the required amount of shear reinforcement
· Allow for rapid and reliable hand-based designs and should be well justified and the required amount of shear
checks of existing designs; reinforcement should be conservative.
