Modification of partial safety factors for a semi-probabilistic evaluation of existing timber structures
Abstract
The evaluation of the load-bearing capacity of existing structures is a central and important part in the work of structural engineers. Currently, engineers are confronted with the challenge of applying design rules developed for new structures in the evaluation of existing ones as no specific recommendations exist on a European level. As a contribution to this, a first step of this study is the evaluation of the reliability level of timber elements subjected to common limit states. Based on these analyses, modifications of the target reliability and of partial safety factors (PSF) for existing structures on the resistance side are studied. Considering a modification of the target reliability, the PSF for the material strength could be proposed with 
for compressive and flexural strength in limit states, where variable actions are present. Additionally, options for incorporating updated material parameters from a survey on site supported by technical devices are discussed and further need for research is identified. Subsequently, this paper provides a stepwise evaluation procedure including modified PSF considering both, an update of the target reliability and update of the material parameters obtained by a survey on site and is thus adaptive for different individual cases and level of information.
First published online 10 February 2025
Keyword : timber, existing buildings, semi-probabilistic evaluation, code calibration
How to Cite
Loebjinski, M., Li, Z., Rug, W., & Pasternak, H. (2022). Modification of partial safety factors for a semi-probabilistic evaluation of existing timber structures. Engineering Structures and Technologies, 14(1), 7–23. https://doi.org/10.3846/est.2022.23007
This work is licensed under a Creative Commons Attribution 4.0 International License.
References
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Diamantidis, D., & Bazzurro, P. (2007). Safety acceptance criteria for existing structures. In Conference: Workshop on Risk Acceptance and Risk Communication, Stanford University, USA.
Diamantidis, D., Holický, M., & Sýkora, M. (2016a). Reliability and risk acceptance criteria for civil engineering structures. Transactions of the VŠB – Technical University of Ostrava. Civil Engineering Series, 16(2), 1–10. https://doi.org/10.1515/tvsb-2016-0008
Diamantidis, D., Holický, M., & Sýkora, M. (2016b). Risk and reliability acceptance criteria for civil engineering structures. In Conference: Structural Reliability and Modelling in Mechanics. Ostrava, Czech Republic.
Diamantidis, D., Holický, M., & Sýkora, M. (2017). Target reliability levels based on societal, economic and environmental consequences of structural failure. In 12th International Conference on Structural Safety and Reliability (ICOSSAR) (pp. 644–653). Vienna.
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Fischer, A. M. (2010). Bestimmung modifizierter Teilsicherheitsbeiwerte zur semiprobabilistischen Bemessung von Stahlbetonkonstruktionen im Bestand [Dissertation]. Technische Universität Kaiserslautern. Retrieved March 29, 2016, from https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2259
Glowienka, S. (2007). Zuverlässigkeit von Mauerwerkswänden aus großformatigen Steinen: Probabilistische Analyse von großformatigem Mauerwerk aus Kalksandstein und Porenbeton mit Dünnbettvermörtelung [Dissertation]. Technische Universität Darmstadt.
Grünberg, J. (2004). Grundlagen der Tragwerksplanung – Sicherheitskonzept und Bemessungsregeln für den konstruktiven Ingenieurbau: Erläuterungen zu DIN 1055-100 (1. Aufl.). Praxis Bauwesen. Beuth.
Hasofer, A. M., & Lind, N. C. (1974). An exact and invariant first-order reliability format. Journal of the Engineering Mechanics Division, 100(1), 111–121. https://doi.org/10.1061/JMCEA3.0001848
Holický, M., & Sýkora, M. (2016). Probabilistic models for wind actions. In 2016 Second International Symposium on Stochastic Models in Reliability Engineering, Life Science and Operations Management (SMRLO). IEEE. https://doi.org/10.1109/SMRLO.2016.38
Hösl, M., & Dietsch, P. (2010). Assessment of timber structures. In H. Brüninghoff & P. Dietsch (Eds.), Berichte aus dem Bauwesen. Assessment of timber structures. COST action E55 – Modelling of the performance of timber structures (pp. 14–21). Shaker Verlag.
International Organization for Standardization. (2010, August 01). Bases for design of structures – Assessment of existing structures (ISO Standard No. ISO 13822:2010).
International Organization for Standardization. (2015). General principles on reliability for structures (ISO Standard No. ISO 2394:2015).
Spanos, P. D., & Wu, I. T. (Eds.) (1993). Probabilistic structural mechanics: Advances in structural reliability methods. IUTAM Symposium, San Antonio, Texas, USA. Springer. https://doi.org/10.1007/978-3-642-85092-9
Joint Committee on Structural Safety. (2001a). Probabilistic Model Code: Part 1 – Basis of Design. Retrieved March 07, 2016, from https://www.jcss-lc.org/jcss-probabilistic-model-code/
Joint Committee on Structural Safety (2001b). Probabilistic Model Code: Part 2 – Load Models. Retrieved March 29, 2016, from https://www.jcss-lc.org/jcss-probabilistic-model-code/
Joint Committee on Structural Safety. (2006). Probabilistic Model Code: Part 3 – Resistance Models. Retrieved March 08, 2016, from https://www.jcss-lc.org/jcss-probabilistic-model-code/
Joint Research Centre. (2015). New European technical rules for the assessment and retrofitting of existing structures (EUR, Scientific and technical research series). European Commission, Luxembourg.
Kasal, B., & Tannert, T. (2011). In situ assessment of structural timber. Springer Netherlands. https://doi.org/10.1007/978-94-007-0560-9
Köhler, J. (2010). Quantitative assessment – updating. In H. Brüninghoff & P. Dietsch (Eds.), Berichte aus dem Bauwesen. Assessment of timber structures. COST action E55 – Modelling of the performance of timber structures (pp. 120–134). Shaker Verlag.
Köhler, J. (2011). Die Aktualisierung als zentrales Element in den Erhaltungsnormen – Aspekte der Probabilistik. In H. Bahnholzer (Ed.), Dokumentation SIA: D 0240. Erhaltung von Tragwerken – Vertiefung und Anwendung. Unterlagen zu den Einführungskursen (pp. 33–36). Zürich.
Kotlínová, M., Kloiber, M., Vasconcelos, G., Loureno, P. B., & Branco, J. M. (2008). Evaluation of wood density by means of distinct NDT. In L. Binda, M. di Prisco, & R. Felicetti (Eds.), On Site Assessment of Concrete, Masonry and Timber Structures – SACoMaTiS 2008 (pp. 1061–1070). RILEM Publications SARL.
Linke, G., Rug, W., & Pasternak, H. (2022). Strength grading of timber in historic structures – methodology and practical application. In 6th International Conference on Structural Health Assessment of Timber Structures (SHATiS) (pp. 63–68).
Loebjinski, M. (2021). Bewertung der Tragfähigkeit von Holzkonstruktionen beim Bauen im Bestand: Ein Beitrag zur substanzschonenden Erhaltung von bestehenden Gebäuden [Dissertation]. Brandenburgische Technische Universität, Cottbus. http://d-nb.info/1241545375/34
Loebjinski, M., Köhler, J., Rug, W., & Pasternak, H. (2019a). Development of an optimisation-based and practice orientated assessment scheme for the evaluation of existing timber structures. In 6th International Symposium on Life-cycle Analysis and Assessment in Civil Engineering (IALCCE) (pp. 353–360). CRC Press.
Loebjinski, M., Linke, G., Rug, W., & Pasternak, H. (2019b). Redevelopment of a wooden roof construction under preservation order. In 5th International Conference on Structural Health Assessment of Timber Structures (SHATiS) (pp. 912–921). Guimarães, Portugal.
Loebjinski, M., Rug, W., & Pasternak, H. (2020). The influence of improved strength grading in situ on modelling timber strength properties. Buildings, 10(2), Article 30. https://doi.org/10.3390/buildings10020030
MathWorks. (2016). MATLAB. https://www.mathworks.com/products/matlab.html
McAllister, T. P., Wang, N., & Ellingwood, B. R. (2018). Risk-Informed mean recurrence intervals for updated wind maps in ASCE 7-16. Journal of Structural Engineering, 144(5), Article 6018001. https://doi.org/10.1061/(ASCE)ST.1943-541X.0002011
Melchers, R. E. (1999). Structural reliability analysis and prediction (2. ed.). Wiley.
Palaia, L., Monfort, J., Sanchez, R., Gil, L., Álvarez, Á., López, V., et al. (2008). Ancient timber structure analysis applying NDT and traditional methods of assessment. In L. Binda, M. di Prisco, & R. Felicetti (Eds.), On Site Assessment of Concrete, Masonry and Timber Structures – SACoMaTiS 2008 (pp. 1135–1143). RILEM Publications SARL.
Piazza, M., & Riggio, M. (2008). NDT methods for the assessment of structural timber: Report on the research carried out at the University of Torento (Italy). In L. Binda, M. di Prisco, & R. Felicetti (Eds.), On Site Assessment of Concrete, Masonry and Timber Structures – SACoMaTiS 2008 (pp. 1039–1047). RILEM Publications SARL.
Pöhlmann, S., & Rackwitz, R. (1981). Zur Verteilungsfunktion von Werkstoffeigenschaften bei kontinuierlich durchgeführten Sortierungen. Materialprüfung, 23(8), 277–278. https://doi.org/10.1515/mt-1981-230808
Raiffa, H., & Schlaifer, R. (2000). Applied statistical decision theory. Wiley.
Saporiti Machado, J., Riggio, M., & Descamps, T. (Eds.) (2015). Combined use of NDT/SDT methods for the assessment of structural timber members. State of the art report. UMONS – Université de Mons.
Schweizerischer Ingenieur- und Architektenverein. (2011). Grundlagen der Erhaltung von Tragwerken (SIA 269:2011). Zürich.
Sørensen, J. D. (2001). Code calibration and timber experience (COST Action E24). Institute of Building Technology and Structural Engineering, Aalborg University, Aalborg.
Sousa, H. S. (2013). Methology for Safety evaluation of existing timber elements [Dissertation]. Universidade do Minho Escola de Engenharia.
Sousa, H. S., Branco, J. M., & Lourenço, P. B. (2015a). A Holistic methodology for probabilistic safety assessment of timber elements combining onsite and laboratory data. International Journal of Architectural Heritage, 10(5), 526–538. https://doi.org/10.1080/15583058.2015.1007177
Sousa, H. S., Machado, J. S., Branco, J. M., & Lourenço, Paulo, B. (2015b). Onsite assessment of structural timber members by means of hierarchical models and probabilistic models. Construction and Building Materials, 101, 1185–1196. https://doi.org/10.1016/j.conbuildmat.2015.05.127
Spaethe, G. (1992). Die Sicherheit tragender Baukonstruktionen (2nd ed.). Springer-Verlag. https://doi.org/10.1007/978-3-7091-6690-1
Stauder, F. (2015). Zuverlässigkeitskonzept für bestehende Tragwerke im Wasserbau [Dissertation]. Technische Universität Kaiserslautern, Kaiserslautern.
Steenbergen, R., Sýkora, M., Diamantidis, D., Holický, M., & Vrouwenvelder, T. (2015). Economic and human safety reliability levels for existing structures. Structural Concrete, 16(3), 323–332. https://doi.org/10.1002/suco.201500022
Turkstra, C. J. (1970). Theory of Structural Design Decisions: Study No. 2. Ontario, Canada.
Vrouwenvelder, T. (2001). Reliability based code calibration – The use of the JCSS probabilistic model code. JCSS, Workshop on Code Calibration, Zürich.
Vrouwenvelder, T. (2002). Developments towards full probabilistic design codes. Structural Safety, 24, 417–432. https://doi.org/10.1016/S0167-4730(02)00035-8
Baravalle, M. (2017). Risk and reliability based calibration of structural design codes [Dissertation]. Norwegian University of Science and Technology, Trondheim.
Baravalle, M., & Köhler, J. (2017). A framework for estimating the implicit safety level of existing design codes. In 12th International Conference on Structural Safety and Reliability (ICOSSAR) (pp. 1037–1046). Vienna.
Benjamin, J. R., & Cornell, C. A. (1970). Probability, statistics and decision for civil engineers. McGraw-Hill, Inc.
CIB. (1989). Actions on structures: Live loads in buildings (CIB Report No. W81).
Cornell, C. A. (1969). A probability-based structural code. ACI Journal, 66(12), 974–985. https://doi.org/10.14359/7446
Deutsches Institut für Normung. (2010, Dezember). Eurocode 5: Bemessung und Konstruktion von Holzbauten – Teil 1-1: Allgemeines – Allgemeine Regeln und Regeln für den Hochbau (Deutsche Fassung EN 1995-1-1:2004 + AC:2006 + A1:2008). Beuth Verlag.
Diamantidis, D., Holický, M., & Jung, K. (2007). Assessment of existing structures – On the applicability of the JCSS recommendations. In M. H. Faber, T. Vrouwenvelder, & K. Zilch (Eds.), Aspects of structural reliability (pp. 15–18). Herbert Utz Verlag.
Diamantidis, D., & Bazzurro, P. (2007). Safety acceptance criteria for existing structures. In Conference: Workshop on Risk Acceptance and Risk Communication, Stanford University, USA.
Diamantidis, D., Holický, M., & Sýkora, M. (2016a). Reliability and risk acceptance criteria for civil engineering structures. Transactions of the VŠB – Technical University of Ostrava. Civil Engineering Series, 16(2), 1–10. https://doi.org/10.1515/tvsb-2016-0008
Diamantidis, D., Holický, M., & Sýkora, M. (2016b). Risk and reliability acceptance criteria for civil engineering structures. In Conference: Structural Reliability and Modelling in Mechanics. Ostrava, Czech Republic.
Diamantidis, D., Holický, M., & Sýkora, M. (2017). Target reliability levels based on societal, economic and environmental consequences of structural failure. In 12th International Conference on Structural Safety and Reliability (ICOSSAR) (pp. 644–653). Vienna.
Ellingwood, B. R. (1992). Status of reliability-based design in North America: Impact for engineered wood constructions. In J. Bodig (Ed.), NATO ASI series E, applied sciences: Vol. 215. Reliability-based design of engineered wood structures. [Proceedings of the NATO Advanced Research Workshop on Reliability-Based Design of Engineered Wood Structures, Florence, Italy, 2–5 June 1991] (pp. 3–19). Kluwer. https://doi.org/10.1007/978-94-015-8044-1_2
European Committee for Standardization. (2010a, December). Eurocode – Basis of structural design (EN 1990:2010-12)
European Committee for Standardization. (2010b, December). Eurocode 5: Design of timber structures – Part 1-1: General – Common rules and rules for buildings (EN 1995-1-1:2010-12).
European Committee for Standardization. (2019). Conservation of cultural heritage. Historic timber structures. Guidelines for the on-site assessment of load-bearing timber structures (CEN Standard No. EN 17121:2019-12).
European Committee for Standardization. (2020, October). Assessment and retrofitting of existing structures (CEN Standard No. CEN/TS 17440:2020).
Fachkommission Bautechnik der Bauministerkonferenz (ARGEBAU). (2008). Hinweise und Beispiele zum Vorgehen beim Nachweis der Standsicherheit beim Bauen im Bestand. Retrieved January 15, 2016, from https://www.bauministerkonferenz.de/IndexSearch.
Ferry Borges, J., & Castanheta, M. (1971). Structural safety (2 ed.). Lisbon.
Fédération internationale du betón. (2016). Partial factor methods for existing concrete structures. Recommendation (fib bulletin, vol. 80). Lausanne, Switzerland.
Fischer, A. M. (2010). Bestimmung modifizierter Teilsicherheitsbeiwerte zur semiprobabilistischen Bemessung von Stahlbetonkonstruktionen im Bestand [Dissertation]. Technische Universität Kaiserslautern. Retrieved March 29, 2016, from https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2259
Glowienka, S. (2007). Zuverlässigkeit von Mauerwerkswänden aus großformatigen Steinen: Probabilistische Analyse von großformatigem Mauerwerk aus Kalksandstein und Porenbeton mit Dünnbettvermörtelung [Dissertation]. Technische Universität Darmstadt.
Grünberg, J. (2004). Grundlagen der Tragwerksplanung – Sicherheitskonzept und Bemessungsregeln für den konstruktiven Ingenieurbau: Erläuterungen zu DIN 1055-100 (1. Aufl.). Praxis Bauwesen. Beuth.
Hasofer, A. M., & Lind, N. C. (1974). An exact and invariant first-order reliability format. Journal of the Engineering Mechanics Division, 100(1), 111–121. https://doi.org/10.1061/JMCEA3.0001848
Holický, M., & Sýkora, M. (2016). Probabilistic models for wind actions. In 2016 Second International Symposium on Stochastic Models in Reliability Engineering, Life Science and Operations Management (SMRLO). IEEE. https://doi.org/10.1109/SMRLO.2016.38
Hösl, M., & Dietsch, P. (2010). Assessment of timber structures. In H. Brüninghoff & P. Dietsch (Eds.), Berichte aus dem Bauwesen. Assessment of timber structures. COST action E55 – Modelling of the performance of timber structures (pp. 14–21). Shaker Verlag.
International Organization for Standardization. (2010, August 01). Bases for design of structures – Assessment of existing structures (ISO Standard No. ISO 13822:2010).
International Organization for Standardization. (2015). General principles on reliability for structures (ISO Standard No. ISO 2394:2015).
Spanos, P. D., & Wu, I. T. (Eds.) (1993). Probabilistic structural mechanics: Advances in structural reliability methods. IUTAM Symposium, San Antonio, Texas, USA. Springer. https://doi.org/10.1007/978-3-642-85092-9
Joint Committee on Structural Safety. (2001a). Probabilistic Model Code: Part 1 – Basis of Design. Retrieved March 07, 2016, from https://www.jcss-lc.org/jcss-probabilistic-model-code/
Joint Committee on Structural Safety (2001b). Probabilistic Model Code: Part 2 – Load Models. Retrieved March 29, 2016, from https://www.jcss-lc.org/jcss-probabilistic-model-code/
Joint Committee on Structural Safety. (2006). Probabilistic Model Code: Part 3 – Resistance Models. Retrieved March 08, 2016, from https://www.jcss-lc.org/jcss-probabilistic-model-code/
Joint Research Centre. (2015). New European technical rules for the assessment and retrofitting of existing structures (EUR, Scientific and technical research series). European Commission, Luxembourg.
Kasal, B., & Tannert, T. (2011). In situ assessment of structural timber. Springer Netherlands. https://doi.org/10.1007/978-94-007-0560-9
Köhler, J. (2010). Quantitative assessment – updating. In H. Brüninghoff & P. Dietsch (Eds.), Berichte aus dem Bauwesen. Assessment of timber structures. COST action E55 – Modelling of the performance of timber structures (pp. 120–134). Shaker Verlag.
Köhler, J. (2011). Die Aktualisierung als zentrales Element in den Erhaltungsnormen – Aspekte der Probabilistik. In H. Bahnholzer (Ed.), Dokumentation SIA: D 0240. Erhaltung von Tragwerken – Vertiefung und Anwendung. Unterlagen zu den Einführungskursen (pp. 33–36). Zürich.
Kotlínová, M., Kloiber, M., Vasconcelos, G., Loureno, P. B., & Branco, J. M. (2008). Evaluation of wood density by means of distinct NDT. In L. Binda, M. di Prisco, & R. Felicetti (Eds.), On Site Assessment of Concrete, Masonry and Timber Structures – SACoMaTiS 2008 (pp. 1061–1070). RILEM Publications SARL.
Linke, G., Rug, W., & Pasternak, H. (2022). Strength grading of timber in historic structures – methodology and practical application. In 6th International Conference on Structural Health Assessment of Timber Structures (SHATiS) (pp. 63–68).
Loebjinski, M. (2021). Bewertung der Tragfähigkeit von Holzkonstruktionen beim Bauen im Bestand: Ein Beitrag zur substanzschonenden Erhaltung von bestehenden Gebäuden [Dissertation]. Brandenburgische Technische Universität, Cottbus. http://d-nb.info/1241545375/34
Loebjinski, M., Köhler, J., Rug, W., & Pasternak, H. (2019a). Development of an optimisation-based and practice orientated assessment scheme for the evaluation of existing timber structures. In 6th International Symposium on Life-cycle Analysis and Assessment in Civil Engineering (IALCCE) (pp. 353–360). CRC Press.
Loebjinski, M., Linke, G., Rug, W., & Pasternak, H. (2019b). Redevelopment of a wooden roof construction under preservation order. In 5th International Conference on Structural Health Assessment of Timber Structures (SHATiS) (pp. 912–921). Guimarães, Portugal.
Loebjinski, M., Rug, W., & Pasternak, H. (2020). The influence of improved strength grading in situ on modelling timber strength properties. Buildings, 10(2), Article 30. https://doi.org/10.3390/buildings10020030
MathWorks. (2016). MATLAB. https://www.mathworks.com/products/matlab.html
McAllister, T. P., Wang, N., & Ellingwood, B. R. (2018). Risk-Informed mean recurrence intervals for updated wind maps in ASCE 7-16. Journal of Structural Engineering, 144(5), Article 6018001. https://doi.org/10.1061/(ASCE)ST.1943-541X.0002011
Melchers, R. E. (1999). Structural reliability analysis and prediction (2. ed.). Wiley.
Palaia, L., Monfort, J., Sanchez, R., Gil, L., Álvarez, Á., López, V., et al. (2008). Ancient timber structure analysis applying NDT and traditional methods of assessment. In L. Binda, M. di Prisco, & R. Felicetti (Eds.), On Site Assessment of Concrete, Masonry and Timber Structures – SACoMaTiS 2008 (pp. 1135–1143). RILEM Publications SARL.
Piazza, M., & Riggio, M. (2008). NDT methods for the assessment of structural timber: Report on the research carried out at the University of Torento (Italy). In L. Binda, M. di Prisco, & R. Felicetti (Eds.), On Site Assessment of Concrete, Masonry and Timber Structures – SACoMaTiS 2008 (pp. 1039–1047). RILEM Publications SARL.
Pöhlmann, S., & Rackwitz, R. (1981). Zur Verteilungsfunktion von Werkstoffeigenschaften bei kontinuierlich durchgeführten Sortierungen. Materialprüfung, 23(8), 277–278. https://doi.org/10.1515/mt-1981-230808
Raiffa, H., & Schlaifer, R. (2000). Applied statistical decision theory. Wiley.
Saporiti Machado, J., Riggio, M., & Descamps, T. (Eds.) (2015). Combined use of NDT/SDT methods for the assessment of structural timber members. State of the art report. UMONS – Université de Mons.
Schweizerischer Ingenieur- und Architektenverein. (2011). Grundlagen der Erhaltung von Tragwerken (SIA 269:2011). Zürich.
Sørensen, J. D. (2001). Code calibration and timber experience (COST Action E24). Institute of Building Technology and Structural Engineering, Aalborg University, Aalborg.
Sousa, H. S. (2013). Methology for Safety evaluation of existing timber elements [Dissertation]. Universidade do Minho Escola de Engenharia.
Sousa, H. S., Branco, J. M., & Lourenço, P. B. (2015a). A Holistic methodology for probabilistic safety assessment of timber elements combining onsite and laboratory data. International Journal of Architectural Heritage, 10(5), 526–538. https://doi.org/10.1080/15583058.2015.1007177
Sousa, H. S., Machado, J. S., Branco, J. M., & Lourenço, Paulo, B. (2015b). Onsite assessment of structural timber members by means of hierarchical models and probabilistic models. Construction and Building Materials, 101, 1185–1196. https://doi.org/10.1016/j.conbuildmat.2015.05.127
Spaethe, G. (1992). Die Sicherheit tragender Baukonstruktionen (2nd ed.). Springer-Verlag. https://doi.org/10.1007/978-3-7091-6690-1
Stauder, F. (2015). Zuverlässigkeitskonzept für bestehende Tragwerke im Wasserbau [Dissertation]. Technische Universität Kaiserslautern, Kaiserslautern.
Steenbergen, R., Sýkora, M., Diamantidis, D., Holický, M., & Vrouwenvelder, T. (2015). Economic and human safety reliability levels for existing structures. Structural Concrete, 16(3), 323–332. https://doi.org/10.1002/suco.201500022
Turkstra, C. J. (1970). Theory of Structural Design Decisions: Study No. 2. Ontario, Canada.
Vrouwenvelder, T. (2001). Reliability based code calibration – The use of the JCSS probabilistic model code. JCSS, Workshop on Code Calibration, Zürich.
Vrouwenvelder, T. (2002). Developments towards full probabilistic design codes. Structural Safety, 24, 417–432. https://doi.org/10.1016/S0167-4730(02)00035-8