Solution - dm2_080337

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(7) Inspect the results of the analyses.
The following is a summary of the peak response parameters
for the structure on both the loose and very compact
gravel.
Loose Gravel:
Maximum rotation of structure = 36.2deg.
Maximum horizontal displacement of foundation =
10.0 in
Ratio of maximum rotation to overturning angle =
0.70
Very Compact Gravel:
Maximum rotation of structure = 20.1deg.
Maximum horizontal displacement of foundation =
3.80 in
Ratio of maximum rotation to overturning angle =
0.39
Inspection of the above tabulation of the results
indicates that, in both analyses, the structure:
(a) Has reached its peak response
(b) Did not overturn
(c) Did not experience excessive horizontal
(sliding) displacements.
Therefore, the design proceeds to the next step.
(8) Inspection of the results (peak rotations) summarized in
Step 7 indicates that no further modifications of the
foundation dimensions for overturning or sliding are
required; therefore, the design can proceed to the next
step.
(9) Determine the location of the critical section for shear.
*ln = 6.50 ft or 78.0 in
TS = 7.81 ft or 94.0 in
Assume 4 inches for the bottom cover and tension
reinforcement:
d = 94.0 - 4.0
= 90.0 in
*ln/d = 78.0/90.0
= 0.87 < 5.0
According to the provisions of paragraph 2.c. of this
section, the foundation is considered a thick section and
the critical section for shear is 0.15 *ln from the face
of the support:
*lcr = 0.15 *ln
= 0.15(78)
= 11.7 inches from the haunch (see Figure 93)
2.08-320