Load-deformation behaviour of foundations under vertical and oblique loads

Johnson, Kate (2005) Load-deformation behaviour of foundations under vertical and oblique loads. PhD thesis, James Cook University.

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Abstract

The work in this thesis explores the load-deformation behaviour of shallow and pile foundations under axial and oblique loads.

A statistical review was performed on five popular shallow foundation settlement methods, which showed that different prediction methods could give highly variable results for the same foundation and soil conditions. The probability of failure charts allowing direct comparison between methods is presented, based on the statistical work.

There are 40+ settlement methods available for predicting the settlement of shallow foundations in granular soil. There is no way to account for the differences between settlement methods, other than assume one specific design criterion for every method. For example, limiting the settlement of a shallow foundation to 25 mm is a design criterion that is commonly used. From previous statistical work, it is shown that the Terzaghi and Peck method is more conservative than the method developed by Berardi and Lancellotta. The work in this thesis produced 'probability of failure charts', and the charts give the probability that the settlement for the commonly used methods will exceed an actual design value in the field. These charts allow users to design shallow foundations on the basis of an acceptable failure probability, instead of using one settlement criterion for every settlement method.

A finite element analysis was performed on obliquely loaded piles. The analysis showed that the axial and lateral load components, and moment capacity of a pile is reduced if multiple load types act in unison. Combination loading also affects the pile head displacement. The oblique interaction charts herein allow the ultimate capacity and pile head displacement for a pile under combination loading to be estimated. From the literature review of pile foundations, it is found that the influence due to combination loading is not well defined (i.e. axial loads, lateral loads and moments all acting at once). Previous work has shown that combination loading reduces the ultimate capacity of a pile, and the influence on pile head displacement has not been quantified. The influence of combination loading on pile capacity and settlement was explored, with the use of a finite element computer package entitled ABAQUS. The results from the numerical modelling are summarised into easy-to-use design charts, allowing the user to quantify the reduction in ultimate capacity and influence in settlement.

Item ID: 1313
Item Type: Thesis (PhD)
Keywords: load-deformation behaviour, shallow and pile foundations, axial and oblique loads, statistical review, shallow foundation settlement methods, probability of failure charts, finite element analysis, obliquely loaded piles, axial and lateral load components, moment capacity, combination loading, ultimate capacity, pile head displacement, easy-to-use design charts
Date Deposited: 04 Jan 2007
FoR Codes: 09 ENGINEERING > 0905 Civil Engineering > 090506 Structural Engineering @ 100%
SEO Codes: 87 CONSTRUCTION > 8799 Other Construction > 879999 Construction not elsewhere classified @ 100%
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