1457
Technical Committee 203 /
Comité technique 203
Figure 4 (a) DM and EDP relationship (b)
and DM relationships
Figure 5 Scheme of seismic PBD for piles suggested
3. LOAD CAPACITIES FROM APILE AND LPILE
ANALYSIS
In order to find out the capacities of the numerical piles,
APILE and LPILE programs (Ensoft, Inc.) were adopted in this
study. The axial and lateral capacities of the piles were
analyzed respectively. With the presumed soil parameters and
appropriate soil models of
t-z
,
Q-z
and
P-y
relationships (see
Table 1, the monotonic load-displacement curves of the piles
were computed. A variety of methods can be used to interpret
the axial and lateral capacities of the pile. Based on the local
experiences, the vertical pile capacity was interpreted using the
methods suggested by AASHTO (2002), Fuller and Hoy (1970)
and Chin (1970), whereas the lateral pile capacity was
interpreted by the methods of McNulty (1956), Pyke (1984)
and Manoliu et al. (1985). Table 3 summarizes the results
obtained from the study. It can be seen for the axial capacity,
the order of predictions is such that Chin>F&H>AASHTO. For
the lateral capacity, the order is Manoliu>Pyke>McNulty. One
must know that these predictions are only used for preliminary
design investigations. To ensure that the calculations are
appropriate compared to the real conditions, pile load tests
and/or other types of in-situ testing techniques for pile
capacities must be performed. As mentioned in above
paragraph, LPILE can be used to reveal the moment capacity
of the pile. Figure 6 depict the moments for a concrete pile to
crack (Mcr) and the corresponding curvatures of the pile under
the influences of pile diameter and axial load, presuming that
the area ratio of the steel bar Ar is 2%. One can find similar
results for My and Mult. The pile diameter and the area ratio of
the steel bar will significantly affect the moment capacities.
One can find the observations in Figure 7. Moreover by
changing the pile diameters and fixing other design parameters,
the maximum pile bending moments exerted on the piles can
be found at different seismic PGAt. Figure 8 shows the result
obtained from EQWEAP using the record at one of the seismic
stations. This calculation can be expanded by using many
seismic records as well. In that case, the final results would be
more representative to the seismic design for piles. With a
series of calculations on piles of a certain length, the engineer
can establish a set of monographs for design purpose. Figure 9
suggests the procedures to be taken. A satisfactory design
requires that any mobilized maximum bending moment of the
pile to be less than the moment capacities at the seismic levels
of interest. In the monographs, the stop of the arrow lines must
in the shaded regions to satisfy the design requirements.
Table 3 Pile capacities from various interpretations
Vertical capacities (kN)
Method\D
0.5m 0.75m 1m 1.25m 1.5m 1.75m 2m
AASHTO
1500 3000 4800 6650 8550 10800 13350
Fuller and
Hoy
5200 9400 14000 17600 23950 29500 35400
Chin
6501 9867 15078 20509 28692 34550 43546
Lateral capacities (kN)
Method\D
0.5m 0.75m 1m 1.25m 1.5m 1.75m 2m
McNulty
140 220
340
500
680
880 1140
Pyke
250 500
900 1600 2750 3800 5200
Manoliu,
et al.
340 785 1399 2228 3306 4800 6598
Figure 6 Effects of pile diameter and vertical load on Mcr
Figure 7 Effects of pile diameter and Ar on moment capacities
0
40
80
120
Maximum Displacement (cm)
0
100
200
300
400
Maximum Moment (10^2kN-m)
PGA=0.12g
PGA=0.29g
PGA=0.51g
0
200
400
600
Maximum Moment (10^2kN-m)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Annual Probability of Exceedance (1/year)
0
2000
4000
6000
8000
Cracking Moment (kN-m)
0.0
0.5
1.0
1.5
2.0
Diameter of Pile (m)
E=3.0E+07(kN/m
2
)
Mc=684.31D
2.3819
(0~3600kN)
Mc=1101.7D
2.0235
(3600~7200kN)
Mc=1455.8D
1.9187
(7200~10800kN)
Mc=1764.5D
1.8532
(10800~14400kN)
Mc=2134.2D
1.7835
(14400~18000kN)
0.0
0.5
1.0
1.5
2.0
Pile Diameter (m)
0.000
0.001
0.002
0.003
0.004
Cracking Curvature (rad/m)
E=3.0E+07(kN/m
2
)
Cc=0.0004D
-1.667
(0~3600kN)
Cc=0.0007D
-2.065
(3600~7200kN)
Cc=0.0009D
-2.183
(7200~10800kN)
Cc=0.0011D
-2.27
(10800~14400kN)
Cc=0.0013D
-2.361
(14400~18000kN)
0.0E+0
4.0E-3
8.0E-3
1.2E-2
1.6E-2
Curvature (rad/m)
0
5000
10000
15000
20000
Moment (kN-m)
PercentageofSteel=1.94%
DiameterofPile=0.5m
DiameterofPile=1m
DiameterofPile=2m
M
u
,
ψ
u
0.0E+0
4.0E-3
8.0E-3
1.2E-2
Curvature (rad/m)
0
1000
2000
3000
4000
Moment (kN-m)
DiameterofPile=1m
PercentageofSteel=1.04%
PercentageofSteel=1.94%
PercentageofSteel=3.04%
M
u
,
ψ
u
