DESIGN SPECIFICATIONS FOR HIGHWAY BRIDGES - IISEE

h i = h
M
yi
1 D ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ (10.7.1)
M
2
y B
where
hi
: Height from the pier bottom to the i-th cut-off position of axial reinforcement
(mm)
h : Height from the pier bottom to the height of the superstructural inertial force
(mm)
Myi: Yield bending moment of the section from the pier bottom to i-th cut-off portion
of the axial reinforcement (N・mm)
MyB: Yield bending moment at the pier bottom section (N・mm)
D : Smaller dimension of the pier, in the longitudinal and transverse directions to
the bridge axis. In the case of a circular section, D shall be taken as the
diameter of the section.
(3) When the cut-off of the longitudinal reinforcement at mid-height of a pier is allowed,
the following structural details shall be considered:
1) Cut-off of the longitudinal reinforcement at mid-height of the pier shall not be
located within the area of four times the length of a plastic hinge.
2) A reduction rate in the amount of axial reinforcement at a cut-off position shall not
exceed 1/3. Notwithstanding this, in the case reduction is carried out at different
heights in both the longitudinal and transverse directions, the reduction rate shall be
determined individually at each section.
3) Within a section with height of 1.5 times of either the smaller dimension of a
rectangular pier or the diameter of a circular pier measuring towards both above and
below the cut-off position, the spacings of the hoop ties shall not exceed 150 mm.
Furthermore, as mentioned in Section 10.6 (2), the spacings of the hoop ties shall not
be altered abruptly.
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