d = Vu/vc
d = distance from extreme compression fiber to tension steel, in
Vu = peak applied shear load, lb/in
vc = permissible shear stress carried by concrete, psi
(13) Determine the area of the flexural (main) reinforcement
required using the peak applied bending moment (at the face of the support)
in Equation (158). At the same time, compute the main reinforcement,
according to the provisions of Table 31.
(14) Determine the actual thickness of the foundation using
the following equation:
Tc = d + db/2 + c
Tc = thickness of foundation, in
d = distance from extreme compression fiber to centroid of
tension reinforcement, in
db = diameter of tension reinforcement bar, in
c = thickness of bottom concrete cover specified in Section 7.14
of the ACI Code (always 3 inches).
Depending on the configuration of the structure, a significant decrease in
the foundation thickness could result in a substantial increase in the peak
rotation of the structure. This is generally the case with cantilever wall
barriers; therefore, if the foundation thickness computed is much less than
the thickness used in the overturning analysis, repeat the analysis with the
revised foundation thickness in order to verify the final design. The
verification analysis is generally not required for single cell barriers.
(1) Configuration of the structure and details of the wall
which is designed to the incipient failure conditions
(2) Quantity of explosive: three charges of TNT each
weighing 1,900 lb and located as shown in Figure 92.