Analysis of pile behaviour using constrained optimisation

Although pile load tests provide the most accurate information about load-deformation behaviour of piles, they are usually time-consuming and expensive. Therefore, it would be useful to formulate analytical models based on past data, coupled with essential but minimal pile load tests, to predict pil...

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Main Author: Chan, Chin Loong
Other Authors: Low Bak Kong
Format: Theses and Dissertations
Published: 2008
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Online Access:http://hdl.handle.net/10356/2412
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Institution: Nanyang Technological University
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spelling sg-ntu-dr.10356-24122023-03-03T19:22:53Z Analysis of pile behaviour using constrained optimisation Chan, Chin Loong Low Bak Kong School of Civil and Structural Engineering DRNTU::Engineering::Civil engineering::Geotechnical engineering Although pile load tests provide the most accurate information about load-deformation behaviour of piles, they are usually time-consuming and expensive. Therefore, it would be useful to formulate analytical models based on past data, coupled with essential but minimal pile load tests, to predict pile behaviour. There are already in existence several computer programs that are able to accomplish this using the finite element or finite difference methods. The objective of this project is to conduct such deterministic analyses via commercially available spreadsheet software. All analyses in this research were performed using the widely used Microsoft Excel equipped with an optimisation tool (Solver) and a programming environment(Visual Basic for Applications, VBA). The deterministic numerical procedure is based on constrained optimisation in spreadsheet with minimum amount of programming. Soil resistance are modelled using springs, whose force-displacement relationships are characterised by either ‘t-z’or‘p-y’curves. Several case studies are presented, in which the numerical solutions are compared with experimental data and, where available, with solutions of other software. One particular advantage of the spreadsheet approach in the analysis of laterally loaded piles is the modelling of nonlinear pile flexural rigidity (EPIP), coupled with the use of nonlinear ‘p-y’curves. The deterministic study is then extended to stochastic or reliability analysis on the same spreadsheet platform, taking into consideration uncertainties in soil and pile properties as well as applied loading. The measure of reliability is the Hasofer-Lind (1974) β index, computed based on the alternative perspective of an expanding ellipsoid in the original space of the variables (Low and Tang, 1997). From the β index, one can easily deduce the probability of failure corresponding to a specified limit state. Comparisons are made with simulations (Monte Carlo/Latin Hypcrcube) and the point-estimate method. The ellipsoid optimisation approach provides a relatively easy investigation of multiple modes of failure. By incorporating spatial variability concepts, one can also account for spatial autocorrelation of soil properties. The reliability analysis is then switched to perform reliability-based design, in which the pile length and diameters can be selected to achieve a certain stipulated degree of reliability in one or more limit states. Master of Philosophy (CSE) 2008-09-17T09:02:28Z 2008-09-17T09:02:28Z 2001 2001 Thesis http://hdl.handle.net/10356/2412 Nanyang Technological University application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
topic DRNTU::Engineering::Civil engineering::Geotechnical engineering
spellingShingle DRNTU::Engineering::Civil engineering::Geotechnical engineering
Chan, Chin Loong
Analysis of pile behaviour using constrained optimisation
description Although pile load tests provide the most accurate information about load-deformation behaviour of piles, they are usually time-consuming and expensive. Therefore, it would be useful to formulate analytical models based on past data, coupled with essential but minimal pile load tests, to predict pile behaviour. There are already in existence several computer programs that are able to accomplish this using the finite element or finite difference methods. The objective of this project is to conduct such deterministic analyses via commercially available spreadsheet software. All analyses in this research were performed using the widely used Microsoft Excel equipped with an optimisation tool (Solver) and a programming environment(Visual Basic for Applications, VBA). The deterministic numerical procedure is based on constrained optimisation in spreadsheet with minimum amount of programming. Soil resistance are modelled using springs, whose force-displacement relationships are characterised by either ‘t-z’or‘p-y’curves. Several case studies are presented, in which the numerical solutions are compared with experimental data and, where available, with solutions of other software. One particular advantage of the spreadsheet approach in the analysis of laterally loaded piles is the modelling of nonlinear pile flexural rigidity (EPIP), coupled with the use of nonlinear ‘p-y’curves. The deterministic study is then extended to stochastic or reliability analysis on the same spreadsheet platform, taking into consideration uncertainties in soil and pile properties as well as applied loading. The measure of reliability is the Hasofer-Lind (1974) β index, computed based on the alternative perspective of an expanding ellipsoid in the original space of the variables (Low and Tang, 1997). From the β index, one can easily deduce the probability of failure corresponding to a specified limit state. Comparisons are made with simulations (Monte Carlo/Latin Hypcrcube) and the point-estimate method. The ellipsoid optimisation approach provides a relatively easy investigation of multiple modes of failure. By incorporating spatial variability concepts, one can also account for spatial autocorrelation of soil properties. The reliability analysis is then switched to perform reliability-based design, in which the pile length and diameters can be selected to achieve a certain stipulated degree of reliability in one or more limit states.
author2 Low Bak Kong
author_facet Low Bak Kong
Chan, Chin Loong
format Theses and Dissertations
author Chan, Chin Loong
author_sort Chan, Chin Loong
title Analysis of pile behaviour using constrained optimisation
title_short Analysis of pile behaviour using constrained optimisation
title_full Analysis of pile behaviour using constrained optimisation
title_fullStr Analysis of pile behaviour using constrained optimisation
title_full_unstemmed Analysis of pile behaviour using constrained optimisation
title_sort analysis of pile behaviour using constrained optimisation
publishDate 2008
url http://hdl.handle.net/10356/2412
_version_ 1759855839708971008