(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