Reliability analysis of timber structures

Alpo Ranta-Maunus, Mikael Fonselius, Juha Kurkela, Tomi Toratti

Research output: Book/ReportReport

Abstract

As part of the European harmonisation of building codes, the determination of design values for loads and materials is important and is the motivation for this research. This report begins with a summary of the probabilistic basis of Eurocodes, analyses the strength distributions of wooden materials, demonstrates the effects of different distribution functions on the calculated safety level and shows some results of the applications of reliability analysis. When the number of experiments allows, determination of the 5% fractile of strength should be based on the function fitting on the lower tail of the strength values, for instance 10%. All smooth functions fitted to tail data gave good estimates of the 5% fractile. When the 5% fractile was determined from a function fitted to all data, up to 5% error occurred (in one case 9%) when compared to a non-parametric estimate. Three-parameter Weibull distribution gave, in all calculated cases, the 5% fractile within an accuracy of ±3%. The result of structural reliability analysis depends strongly on the load and strength distribution types used. When fitted functions are used in reliability analysis, it is essential that the fit is good in the lower tail area, the lowest values being most important. When fitted to the same data, a two-parametric Weibull distribution gives the most pessimistic prediction for the tail, with a normal distribution being next, and lognormal and three-parameter Weibull being the most optimistic. In an example, a two-parameter Weibull gave a failure probability 10 times higher than that of a three-parameter Weibull. The analysis suggests that gM = 1.2 to 1.3 is reasonable for timber structures when gG = 1.2 and gQ = 1.5.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages107
ISBN (Electronic)951-38-5909-6
ISBN (Print)951-38-5908-8
Publication statusPublished - 2001
MoE publication typeNot Eligible

Publication series

SeriesVTT Tiedotteita - Meddelanden - Research Notes
Number2109
ISSN1235-0605

Fingerprint

Timber
Reliability analysis
Weibull distribution
Normal distribution
Distribution functions
Experiments

Keywords

  • wooden structures
  • reliability
  • construction
  • timber construction
  • strength
  • building code
  • design
  • plywood
  • Eurocode
  • failure

Cite this

Ranta-Maunus, A., Fonselius, M., Kurkela, J., & Toratti, T. (2001). Reliability analysis of timber structures. Espoo: VTT Technical Research Centre of Finland. VTT Tiedotteita - Meddelanden - Research Notes, No. 2109
Ranta-Maunus, Alpo ; Fonselius, Mikael ; Kurkela, Juha ; Toratti, Tomi. / Reliability analysis of timber structures. Espoo : VTT Technical Research Centre of Finland, 2001. 107 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2109).
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Ranta-Maunus, A, Fonselius, M, Kurkela, J & Toratti, T 2001, Reliability analysis of timber structures. VTT Tiedotteita - Meddelanden - Research Notes, no. 2109, VTT Technical Research Centre of Finland, Espoo.

Reliability analysis of timber structures. / Ranta-Maunus, Alpo; Fonselius, Mikael; Kurkela, Juha; Toratti, Tomi.

Espoo : VTT Technical Research Centre of Finland, 2001. 107 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2109).

Research output: Book/ReportReport

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T1 - Reliability analysis of timber structures

AU - Ranta-Maunus, Alpo

AU - Fonselius, Mikael

AU - Kurkela, Juha

AU - Toratti, Tomi

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N2 - As part of the European harmonisation of building codes, the determination of design values for loads and materials is important and is the motivation for this research. This report begins with a summary of the probabilistic basis of Eurocodes, analyses the strength distributions of wooden materials, demonstrates the effects of different distribution functions on the calculated safety level and shows some results of the applications of reliability analysis. When the number of experiments allows, determination of the 5% fractile of strength should be based on the function fitting on the lower tail of the strength values, for instance 10%. All smooth functions fitted to tail data gave good estimates of the 5% fractile. When the 5% fractile was determined from a function fitted to all data, up to 5% error occurred (in one case 9%) when compared to a non-parametric estimate. Three-parameter Weibull distribution gave, in all calculated cases, the 5% fractile within an accuracy of ±3%. The result of structural reliability analysis depends strongly on the load and strength distribution types used. When fitted functions are used in reliability analysis, it is essential that the fit is good in the lower tail area, the lowest values being most important. When fitted to the same data, a two-parametric Weibull distribution gives the most pessimistic prediction for the tail, with a normal distribution being next, and lognormal and three-parameter Weibull being the most optimistic. In an example, a two-parameter Weibull gave a failure probability 10 times higher than that of a three-parameter Weibull. The analysis suggests that gM = 1.2 to 1.3 is reasonable for timber structures when gG = 1.2 and gQ = 1.5.

AB - As part of the European harmonisation of building codes, the determination of design values for loads and materials is important and is the motivation for this research. This report begins with a summary of the probabilistic basis of Eurocodes, analyses the strength distributions of wooden materials, demonstrates the effects of different distribution functions on the calculated safety level and shows some results of the applications of reliability analysis. When the number of experiments allows, determination of the 5% fractile of strength should be based on the function fitting on the lower tail of the strength values, for instance 10%. All smooth functions fitted to tail data gave good estimates of the 5% fractile. When the 5% fractile was determined from a function fitted to all data, up to 5% error occurred (in one case 9%) when compared to a non-parametric estimate. Three-parameter Weibull distribution gave, in all calculated cases, the 5% fractile within an accuracy of ±3%. The result of structural reliability analysis depends strongly on the load and strength distribution types used. When fitted functions are used in reliability analysis, it is essential that the fit is good in the lower tail area, the lowest values being most important. When fitted to the same data, a two-parametric Weibull distribution gives the most pessimistic prediction for the tail, with a normal distribution being next, and lognormal and three-parameter Weibull being the most optimistic. In an example, a two-parameter Weibull gave a failure probability 10 times higher than that of a three-parameter Weibull. The analysis suggests that gM = 1.2 to 1.3 is reasonable for timber structures when gG = 1.2 and gQ = 1.5.

KW - wooden structures

KW - reliability

KW - construction

KW - timber construction

KW - strength

KW - building code

KW - design

KW - plywood

KW - Eurocode

KW - failure

M3 - Report

SN - 951-38-5908-8

T3 - VTT Tiedotteita - Meddelanden - Research Notes

BT - Reliability analysis of timber structures

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Ranta-Maunus A, Fonselius M, Kurkela J, Toratti T. Reliability analysis of timber structures. Espoo: VTT Technical Research Centre of Finland, 2001. 107 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 2109).