(1) Use equations (10-5) and (10-6) to

10-7c. The repetitive loading will consist of the dead

compute-

load pressure, with the live load increment applied for 1

(a) Minimum and maximum footing sizes

minute. Then release the live load increment and allow

using Es = 1000 and 5000 kips per square foot,

to rebound at the dead pressure for 1 minute. This

respectively.

procedure constitutes one cycle of live load pressure

(b) Two intermediate footing sizes using

application. Deformation readings will be taken at three

values intermediate between 1000 and 5000 kips per

points: at the start, after the live load is applied for 1

square foot.

minute, and after the plate rebounds under the dead load

Use these four values of B or D in the following

pressure for 1 minute. Live load applications will be

equations to compute the increase (or pressure change)

repeated for 15 cycles.

in the live load, ∆L.

(4) Increase the dead load pressure, q0, to

the second lowest value, allow to consolidate, and then

square footing ∆L =

apply the respective live load increment repetitively for 15

17.0M (pounds per

cycles.

3

square foot) (10-7)

B

(5) Repeat step 4 for the remaining two

dead load pressure increments.

round footing ∆L =

20.3M (pounds per

(6) An uncorrected modulus of elasticity

3

D

square foot) (10-8)

value is computed for each increment of dead and live

load pressure as follows:

(2) The Es value depends on the depth of the

25.5 ∆L (1 - )

2

Es' =

footing below grade, the average dead load pressure on

S

the soil, and the maximum pressure change in the live

Es' =

uncorrected effective modulus of

load, ∆L, on the foundation due to wind moments. A

elasticity for the loading condition used, pounds per

determination of the E, value will be made at the

square foot

proposed footing depth for each footing size computed.

S

=

average edge deformation of the plate

(3) The dead load pressure, q0, is computed as

for the applied load, determined from the slope of the last

the weight, W, of the radar tower, appurtenances, and

five rebound increments in the repetitive load test, inches

the footing divided by the footing area, A.

=

Poisson's ratio (see table 3-6).

ΣW

=

(10-9)

q0

(7) The above-computed uncorrected

A

modulus of elasticity will be corrected for bending of the

plate as described in TM 5-824-3/AFM 88-6, Chapter 3,

The selection of loadings for the field plate load test will

where E' is defined above, and E, is the effective

be based on qo and ∆L.

modulus of elasticity for the test conditions.

d. Field plate load test procedure.

The

e. Selection of required footing size. The

following plate load test will be performed at the elevation

required footing size to meet the allowable rotation

of the bottom of the footing, and the test apparatus will

criteria will be determined as follows:

be as described in TM 5-824-3/AFM 88-6, Chapter 3.

(1) Plot on log-log paper the minimum and

(1) Apply a unit loading to the plate equal

the maximum footing size and the two intermediate

to the smallest unit load due to the dead load pressure

footing sizes versus the required (four assumed values)

q0. This unit loading will represent the largest size

effective modulus of elasticity for each footing size.

footing selected above.

(2) Plot the measured effective modulus of

(2) Allow essentially full consolidation

elasticity versus the footing size corresponding to the

under the dead load pressure increment. Deformation

loading condition used for each test on the same chart

readings will be taken intermittently during and at the end

as above.

of the consolidation period.

(3) These two plots will intersect. The

(3) After consolidation under the dead

footing size indicated by their intersection is the minimum

load pressure, perform repetitive load test using the live

footing size that will resist the specified angle of tilt.

load pressure ∆L computed by the formulas in paragraph

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