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Proceedings of the 18
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Proceedings of the 18
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International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
=
(2)
and
are dimensionless constants determined empirically
from the tests. The results from the long-term one-way loading
cf. Figure 5 shows a general good agreement with the power
function even though deviations in the first 1000 cycles are
observed. The values for the power
are found to be similar for
all the tests with values in the range of 0.11 to 0.18. These
values are found to be smaller than the value of 0.31 as
presented by LeBlanc et al. (2010). The results for the constant
cf. Figure 6 indicates that
depends linearly of the magnitude
of the loading
which is in agreement with the findings in
LeBlanc et al. (2010).
Figure 6. Fitted empirical constant
as a function of the loading
magnitude
in the four cyclic tests.
The influence of the cyclic loading on the static lateral
capacity is evaluated by means of the results from the three
static tests performed post cyclic loading cf. Figure 7. The
maximum moments obtained indicates that the lateral capacity
depends on the cyclic loading and increases with increasing
load magnitude.
Figure 7. Moment-rotation relationships obtained in the static tests post
cyclic loading compared with the reference static test.
4 CONCLUSION
This paper presents a description of a 1g laboratory small scale
test setup for modelling laterally long-term cyclic loading of a
stiff pile in saturated dense sand. A static loading test and four
one-way cyclic loading tests with maximum moment loading
equal to 18% to 36% of the maximum static capacity are
presented. The purpose of the tests is to evaluate the influence
of the number of load cycles on the accumulated rocking
rotation of the pile at seabed during long-term cyclic loading. In
addition the effect of the cyclic loading on the static lateral
capacity is evaluated by means of static loading tests conducted
post cyclic loading.
All the tests are carried out with an open ended aluminium
pipe pile scaled approximately 1:50 in relation to a typical
monopile foundation for an offshore wind turbine. In the four
cyclic tests more than 50 000 load cycles are applied to the pile.
When evaluating the cyclic tests the accumulated rotation
normalised with respect to the rotation obtained in the first
loading cycles is used. The results reveal that the accumulation
of rotation during long-term cyclic loading can be described by
use of a power function. Further, the maximum moments
obtained in the static tests conducted post cyclic loading
indicates that the lateral capacity depends on the cyclic loading
and increases with increasing load magnitude.
The entire test setup is still in the initial phase of testing and
can be improved even more. Thus, the findings inhere must be
evaluated further and supplemented with additional testing with
varied loading characteristics, i.e. varied
and
for both one-
and two-way loading.
5 ACKNOWLEDGEMENTS
This research is associated with the EUDP programme
“Monopile cost reduction and demonstration by joint applied
research” funded by the Danish energy sector. The financial
support is sincerely acknowledged.
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