Title:
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Contribution to the static and dynamic response of piles in
liquefiable ground
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New and existing superstructures (such as bridges and buildings) supported on pile
foundations and located in sites susceptible to liquefaction and lateral spreading are required
to be assessed or designed to withstand the actions of extreme loads. As a result, the
performance of the piles, foundations, and also superstructures must be estimated/predicted
by sufficient accuracy using dynamic analysis. Usually a large number of analyses are
required for assessing the performance of a dynamic system and obtaining the analytical
fragility functions, as an example. Simplified-conventional solutions may not be accurate
enough to address the complex dynamic phenomena involved in soil-pile interaction in
liquefiable soil. In order to achieve this, it is necessary to simulate soil-pile system using a
reliable method supported by realistic soil constitutive relations surrounding the pile.
Therefore, a hypo-elastic bounding surface model has been developed in the framework of
the macro-element to underpin and facilitate the concerns of 'performance-based design' and
'risk assessments'. In this case, it is expected that the macro-element approach is able to
feedback quick response with high accuracy comparable to sophisticated and complex Finite
Element (FE) models.
Following the concept of hypo-elasticity, elastic stiffness of the macro-element should be
estimated accurately. In this case, an elasto-dynamic solution has been developed for
analyzing the soil-pile system under the pile-head and the kinematic earthquake loading. This
method is also generalized for different types of pile foundations ranging from the short
piles/caissons to long/flexible piles.
Validations and verifications of the macro-element approach show its high accuracy on
simulating the field test and dynamic centrifuge. It is concluded to move step forward by
utilizing the macro-element for soil-pile system in liquefiable ground in order to produce
precise results.
Finally, a simple method for calculating the dynamic bending moment in pre-liquefaction
phase (cyclic mobility phase) is proposed for the geotechnical desk study using the elastic
continuum solution.
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