312
BEHAVIOR OF PILES SUPPORTING OFFSHORE STRUCTURES
COMPUTATION SHEET
Let Pt = 60,000 1b
Try T = 200 in.
Zmax = 1,500/200 = 7.5 > 5 Use long pile coefficients
From équation (11.21):
St = Mt/6.18 x 109
FYom équation (11.22):
St — (—1.623)(60,000)(200)2/(4.23 x 1011)
-(1.75)(200)M/(4.23 x 1011)
Solve the above two équations simultaneously for Mt.
68.447M = -3.8952 x 109 - 350Mt;
Mt = -9.31 x 106 in.-lb
From équation (11.15):
St = A„(60,000)(200)2/4.23 x 1011
+B„(-9.31) x 106(200)2/(4.23 x 1011)
y =1,13571,, -0.8805s,
Table 11.5 Computed Results for the First Trial
X
in.
Z
in.
Va
in.
B»
ys
in.
y
in.
P
lb/in.
Epy
lb/in.2
0
0
2.435
2.763
1.623 -1.428
1.335
0
0
50 0.25 2.032
2.306
1.210 -1.065
1.241
29.5
24
100 0.50 1.644
1.866
0.873 -0.768
1.098
62.5
57
200 1.00 0.962
1.092
0.364 -0.320
0.772
116.2
151
300 1.50 0.463
0.526
0.070 -0.062
0.464
146.7
316
400 2.00 0.142
0.161
0.007 -0.006
0.155
134.5
868
500 2.50 -0.025
-0.028
0.100 0.088
0.060
73.6
1227
700 3.50 -0.060
-0.068
0.066 0.053 -0.015
25.8
1720
900 4.50 -0.020
-0.022
0
0
0.022
48.6
2209
^PV = 320/395 = 0.81 lb/in.3
T = (4.23 x io^/o.si)9-2 = 221 in.
The Computation Sheet and Table 11.5 show the first trial for a latéral load
Pt =60,000 1b. A relative stiffness factor T of 200 in. was selected. A value
of the pile-head moment Mt was computed and the nondimensional expressions
were used to compute a latéral deflection y at the depth of each of the p-y curves.
The p-y curves of Figure 11.15 were entered with the computed deflection to
obtain a value of p, with which the values of soil modulus Epy were computed.
The values of soil modulus are plotted in Figure 11.16, and the best straight
line passing through zéro is fitted through the plotted points. Somewhat more
weight is given to the points near the mudline in fitting the line. The slope of
the line is the value of kpp, the variation of the soil modulus with depth. The
computed values of kn and T are shown at the bottom of Table 11.5. Note that
the first trial value of T = 200 in. yielded a computed value of T = 221 in.
BEHAVIOR OF PILES SUPPORTING OFFSHORE STRUCTURES
COMPUTATION SHEET
Let Pt = 60,000 1b
Try T = 200 in.
Zmax = 1,500/200 = 7.5 > 5 Use long pile coefficients
From équation (11.21):
St = Mt/6.18 x 109
FYom équation (11.22):
St — (—1.623)(60,000)(200)2/(4.23 x 1011)
-(1.75)(200)M/(4.23 x 1011)
Solve the above two équations simultaneously for Mt.
68.447M = -3.8952 x 109 - 350Mt;
Mt = -9.31 x 106 in.-lb
From équation (11.15):
St = A„(60,000)(200)2/4.23 x 1011
+B„(-9.31) x 106(200)2/(4.23 x 1011)
y =1,13571,, -0.8805s,
Table 11.5 Computed Results for the First Trial
X
in.
Z
in.
Va
in.
B»
ys
in.
y
in.
P
lb/in.
Epy
lb/in.2
0
0
2.435
2.763
1.623 -1.428
1.335
0
0
50 0.25 2.032
2.306
1.210 -1.065
1.241
29.5
24
100 0.50 1.644
1.866
0.873 -0.768
1.098
62.5
57
200 1.00 0.962
1.092
0.364 -0.320
0.772
116.2
151
300 1.50 0.463
0.526
0.070 -0.062
0.464
146.7
316
400 2.00 0.142
0.161
0.007 -0.006
0.155
134.5
868
500 2.50 -0.025
-0.028
0.100 0.088
0.060
73.6
1227
700 3.50 -0.060
-0.068
0.066 0.053 -0.015
25.8
1720
900 4.50 -0.020
-0.022
0
0
0.022
48.6
2209
^PV = 320/395 = 0.81 lb/in.3
T = (4.23 x io^/o.si)9-2 = 221 in.
The Computation Sheet and Table 11.5 show the first trial for a latéral load
Pt =60,000 1b. A relative stiffness factor T of 200 in. was selected. A value
of the pile-head moment Mt was computed and the nondimensional expressions
were used to compute a latéral deflection y at the depth of each of the p-y curves.
The p-y curves of Figure 11.15 were entered with the computed deflection to
obtain a value of p, with which the values of soil modulus Epy were computed.
The values of soil modulus are plotted in Figure 11.16, and the best straight
line passing through zéro is fitted through the plotted points. Somewhat more
weight is given to the points near the mudline in fitting the line. The slope of
the line is the value of kpp, the variation of the soil modulus with depth. The
computed values of kn and T are shown at the bottom of Table 11.5. Note that
the first trial value of T = 200 in. yielded a computed value of T = 221 in.