Reliability and cost models of axial pile foundations

Pile foundations are often used for important structures, and thus, reliability evaluation is an important aspect of the design. Unlike the approach to reliability evaluation used in structural engineering, the traditional procedure used in geotechnical designs addresses uncertainties through high global or partial safety factors, mostly based on past experience. However, this approach to addressing uncertainties does not provide a rational basis for understanding their influence on design. For this reason, and because of regulation codes and social concerns (such as sustainability), geotechnical engineers need to improve their ability to deal with uncertainties and probabilities to help with decision-making. Reliability methods have become increasingly important as decision support tools. The main benefit of reliability analysis is that it provides quantitative information about the parameters (uncertainties) that most significantly influence the behaviour under study. This makes risk control, the determination of the potential causes of adverse effects on the structure, possible. In particular, the design of pile foundations still involves many limitations and uncertainties, particularly when there is not enough investment in soil characterisation and/or pile load tests. In addition to the uncertainties associated with soil characterisation, physical, statistical, spatial and human uncertainties exist. Hence, because it is technically and economically impossible to produce designs of pile foundations in the most unfavourable of cases, it is the engineer’s goal to minimise the risk and limit it to an acceptable level in the most economical manner possible. Towards this, reliability theory needs to be adapted to the needs and objectives of geotechnical engineering. In this subject, the primary purpose of this dissertation is to demonstrate the application of reliability methods to geotechnical design and more particularly to two distinct case studies of vertical single pile foundations under axial loading. This dissertation also presents a simple and practical approach to performing reliability-based design, obtaining valuable information from it. For that purpose, sensitivity and cost analyses were conducted to study the influence of each uncertainty type. Two well-known reliability methods, the first-order reliability method (FORM) and Monte Carlo simulations (MCS) were applied to the case studies for comparison. In addition, reliability-based safety factors were evaluated and discussed. Another purpose of this dissertation is to demonstrate the advantages of employing reliability tools in the decision-making process for pile foundation design. The decision-making related to the economic and research investments required for gathering the information necessary to characterise the uncertainties associated with important random variables, in both pile design and its reliability, is facilitated by the type of balanced analyses presented in this dissertation. It is concluded that, even though the extent to which this can be accomplished depends on the engineer’s knowledge and the project’s budget for investigation, geotechnical engineering definitely benefits from the consideration of reliability in design. It is finally intended to provide knowledge and tools for code harmonisation between structural and geotechnical designs, and also encourage the development of such in geotechnical practice, international standards and conformity in assessment systems.

Name thesis:degree_name

Doutoramento em Engenharia Civil (especialidade em Geotecnia)

Year dc:date.issued

2013

Author dc:creator

• Teixeira, Ana

Advisors dc:contributor.advisor

• Correia, A. Gomes
• Henriques, António Abel

• Costs
• CPT
• Design codes
• FORM
• Geotechnical reliability
• In situ soil investigation
• MCS
• Partial safety factors
• Pile foundation
• PMT
• Probability of failure
• Reliability based design
• Reliability index
• Risk
• SPT
• Uncertainty
• Custos
• Normas de dimensionamento
• Fiabilidade geotécnica
• Ensaios de campo
• Coeficientes parciais de segurança
• Fundações por estaca
• Probabilidade de rotura
• Dimensionamento baseado em técnicas de fiabilidade
• Índice de fiabilidade
• Risco
• Incertezas

Statement dc:rights

• openAccess

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1822/24556

OAI record oai:identifier

http://repositorium.sdum.uminho.pt/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Arepositorium.uminho.pt%3A1822%2F24556