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Characteristic values of geotechnical parameters in Eurocode 7
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.ORCID iD: 0000-0001-5243-4650
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.ORCID iD: 0000-0001-5372-7519
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.ORCID iD: 0000-0001-9615-4861
2019 (English)In: Proceedings of the Institution of Civil Engeneers: Geotechnical Engineering, ISSN 1353-2618, E-ISSN 1751-8563, Vol. 172, no 4, p. 301-311Article in journal (Refereed) Published
Abstract [en]

Lack of harmonisation between reliability-based design and the partial factor method in Eurocode 7 (EN 1997-1:2004) is preventing the widespread introduction of a risk-based concept in geotechnical design. This paper discusses how uncertainties are managed according to EN 1997-1:2004 and possible implications of not harmonising the current safety format with reliability-based design. One of several challenges highlighted is how EN 1997-1:2004 defines the characteristic value and design value. The characteristic value is therein defined based on a classical frequentist approach through a confidence interval. From a Bayesian point of view, the current definition does not treat the characteristic value as an uncertain variable. Consequently, the definitions of the characteristic value and design value in EN 1997-1:2004 feature weak connections between uncertainties in the geotechnical properties and the consequences of failure, as regulated by the target reliability index.

Place, publisher, year, edition, pages
ICE Publishing , 2019. Vol. 172, no 4, p. 301-311
Keywords [en]
codes of practice & standards, geotechnical engineering, risk & probability analysis
National Category
Geotechnical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-255551DOI: 10.1680/jgeen.18.00057ISI: 000475709400002Scopus ID: 2-s2.0-85068838228OAI: oai:DiVA.org:kth-255551DiVA, id: diva2:1340333
Note

QC 20190805

Available from: 2019-08-05 Created: 2019-08-05 Last updated: 2019-08-20Bibliographically approved
In thesis
1. Managing uncertainties in geotechnical parameters: From the perspective of Eurocode 7
Open this publication in new window or tab >>Managing uncertainties in geotechnical parameters: From the perspective of Eurocode 7
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Geotechnical engineering is strongly associated with large uncertainties. Geotechnical site investigations are made only at discrete points and most of a soil volume is never tested. A major issue is therefore how to cost effectively reduce geotechnical uncertainties with respect to structural performance. Managing the geotechnical uncertainties is thus an important aspect of the design process. Guidance on this subject is given in the European design code for geotechnical design, Eurocode 7 (EN 1997), which advocates the use of the partial-factor method, with the added possibility to use the observational method if the uncertainties are large and difficult to assess.This thesis aims to highlight, develop and improve methods to assess the quality and value of geotechnical site investigations through reliability-based design. The thesis also discusses the limitations of the deterministic partial-factor method, according to its EN 1997 definition, and how to better harmonise this design methodology with the risk-based approach of reliability-based design. The main research contributions are: (1) a presented case study showing the importance of and potential gains with a robust framework for statistical evaluation of geotechnical parameters, (2) the discussion on the limitations of the partial-factor method in EN 1997, and (3) the discussion on how to harmonise the EN 1997 definition of the partial-factor method with the risk-based approach of reliability-based design.

Abstract [sv]

Geoteknik förknippas med ett stort antal osäkerheter. Geotekniska undersökningar utförs i diskreta punkter och den absolut största delen av en jordvolym testas aldrig. En viktig fråga inom geotekniken är därför hur man kan minimera osäkerheterna i relation till kostnaderna för undersökningarna och konstruktionens säkerhet. En annan fråga som uppstår när en konstruktion ska dimensioneras är hur osäkerheterna bör hanteras i dimensioneringsprocessen. För detta ges vägledning i de europeiska dimensioneringsprinciperna för geotekniska konstruktioner, Eurokod 7 (EN 1997), som förespråkar partialkoefficientmetoden. Om osäkerheterna är stora och svåra att uppskatta kan observationsmetoden användas som ett komplement. Syftet med denna avhandling är att belysa, utveckla och förbättra metoder för bygg- och anläggningsbranschen att uppskatta kvalité och värde av geotekniska undersökningar. Ett bayesianskt tillvägagångssätt (multivariabel analys) har använts för att utvärdera osäkerheterna relaterade till de geotekniska undersökningarna. Därtill presenterar avhandlingen en diskussion om begränsningarna i partialkoefficientmetoden, enligt definitionen i EN 1997, och hur denna metod kan utvecklas för att bättre harmonisera med sannolikhetsbaserad dimensionering. De huvudsakliga forskningsbidragen är: (1) den presenterade fallstudien som visar vikten, och den potentiella nyttan, av ett robust ramverk för statistisk utvärdering av geotekniska parametrar som grund för sannolikhetsbaserad dimensionering, (2) diskussionen om begränsningarna med partialkoefficientmetoden enligt definitionen i EN1997, och (3) diskussionen om hur partialkoefficientmetoden kan utvecklas för att bättre harmonisera med sannolikhetsbaserad dimensionering.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 79
Series
TRITA-ABE-DLT ; 1924
Keywords
Eurocode 7, Characteristic value, Partial-factor method, Reliability-based design
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-256058 (URN)978-91-7873-249-4 (ISBN)
Public defence
2019-09-19, Kollegiesalen, Brinellvägen 8, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council FormasSwedish Transport Administration
Note

QC 20190822

Available from: 2019-08-22 Created: 2019-08-20 Last updated: 2019-08-22Bibliographically approved

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Prästings, AndersSpross, JohanLarsson, Stefan

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