Buckling of slender composite piles in soft soils - A comparative study between the Swedish analytical method and 3D Finite Element
Type
Examensarbete för masterexamen
Programme
Date
2020
Authors
Nordström, Rasmus
Model builders
Journal Title
Journal ISSN
Volume Title
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Abstract
When designing piles in Sweden today an analytic method is used exclusively to calculate
the piles structural bearing capacity with regards to buckling (buckling of the 2nd order). A
geometrical instability arises when composite piles, made from steel and concrete, are designed
according to Eurocode 4 "Design of composite structures". While the Swedish analytical
method consider the plastification of the surrounding soil with elastic conditions in the pile
member. These assumption in both methods rises the question of how to design for ULS
with composite piles. The study was made as a comparison between the traditional Swedish
analytical method and a 3D numerical model using the program Tochnog Professional. The
numerical model was shown to replicate the real life failure mechanisms of buckling of a
composite slender pile, but yield point was off. A reason might be the difficulty of modeling the
confinement effects of the concrete part of the model. The study concluded that the numerical
model overpredicts the capacity compared to the analytical when the soil is the design factor for
capacity and underpredicts the capacity when the cross section is the design factor for capacity.
The most critical parameter for the analytical method is the initial bow imperfection. This is
something that is not modeled in the numerical model because of restrictions in the modeling
process.
Description
Keywords
Buckling of composite piles , slender piles , Swedish pile commision report 96 , soft soil , Tochnog Professional