|Description / Abstract
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| EXECUTIVE SUMMARY
The uncertainties affecting the responses of single laterally loaded
offshore pile are identified, analyzed and subsequently incorporated
in the reliability evaluation of pile performance under lateral
loading. Three modes of performance are studied, including: (i)
excessive displacement at the pile head; (ii) initial yielding of
steel pile (damage); and (iii) ultimate yielding of steel pile
(collapse). Probabilistic models are developed to predict the
respective performances. The statistics of the input parameters to the
models are assessed with respect to available data. Reasonable
estimates or range of statistics are also assumed wherever data is
lacking. The following are major results and conclusions.
(1) Statistics (bias and error) of the model correction factor
associated with current design procedures are assessed based on
available field test data for single lateral pile in soft clay, stiff
clay and sand. Substantial discrepancy exists on the statistics
between types of response considered, soil stratum involved and
particularly between piles with fixed and free head condition.
(2) Current design procedures underestimate lateral responses in clay,
but overestimate those in sand.
(3) Uncertainties in the lateral load is the dominant source of
overall response uncertainty, followed by those in the model. Soil
parameters generally have minimal contribution except modulus k for
the case of sand.
(4) For piles in soft clay designed with a safety factor of 2.0, the
probability of initial yielding over a period of 20 years is about
10−2 to 10−3. That for the stiff clay case is comparable,
but the probability for the sand case is down to about 10−5.
(5) The probability of ultimate yielding is generally one to two
orders of magnitude less than that of initial yielding. Hence,
substantial reserve capacity is apparently available after first
(6) Probability of pile head displacement exceeding 10% pile diameter
is about 10−2 for the soft clay case; it becomes almost
negligible for the case of stiff clay or sand.
(7) Statistics of model correction factors for lateral pile groups are
assessed based on available field test data. Reliability procedures
developed for the single laterally loaded pile could be extended to
|Additional Supplemental Documents