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 (10) Determine the peak shear (and the corresponding bending
moment) at the critical section for shear and the peak
bending moment at the face of the support. These
quantities are computed for the response of the structure
on the compact gravel. (Although these quantities are
computed by the program, the hand calculation is
presented to illustrate the procedure.)
The soil bearing pressures at three time stations are
investigated. Figure 93 shows the location of the
critical sections for shear and bending on the foundation
extension. The locations of the soil element attachment
points are also shown in the figure. The pressure
distribution for which the shears and bending moments are
computed are shown in Figure 94. The shears and bending
moment are computed for a 1-inch wide segment of the
foundation extension.
At t = 0.0428 second:
Pcr = (479.5 - 233.6)46.9 + 233.6
4(28.3)
= 335.5 psi
Ps = (479.5 - 233.6)35.2 + 233.6
4(28.3)
= 310.1 psi
Vu = (335.5 + 479.5)66.3
2
= 27,017 lb/in
Mu = 310.1(78)2 + (479.5 - 310.1)(78)2
2
3
= 1,286,867 in-lb/in
At t = 0.05356 second:
Pcr = (549.7 - 311.4)18.6 + 311.4
3(28.3)
= 363.6 psi
Ps = (549.7 - 311.4)6.9 + 311.4
3(28.3)
= 330.6 psi
Vu = (363.6 + 549.7)66.3
2
= 30,276 lb/in
Mu = 330.6(78)2 + (549.7 - 330.6)(78)2
2
3
= 1,450,020 in-lb/in
2.08-322
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