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Heat transfer modelling for timber connections in fire considering uncertainty quantification
Sulon, D. 2025. Heat transfer modelling for timber connections in fire considering uncertainty quantification. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/6e44f2e3-042f-4543-a69d-898f6d59ae48
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613913760137216 |
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| access_status_str | Open Access |
| author | Sulon, Darren Anthony |
| author2 | De Koker, Nico |
| author_browse | De Koker, Nico Sulon, Darren Anthony |
| author_facet | De Koker, Nico Sulon, Darren Anthony |
| author_sort | Sulon, Darren Anthony |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Sulon, D. 2025. Heat transfer modelling for timber connections in fire considering uncertainty quantification. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/6e44f2e3-042f-4543-a69d-898f6d59ae48 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132284 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:41.995Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132284 Heat transfer modelling for timber connections in fire considering uncertainty quantification Sulon, Darren Anthony De Koker, Nico Walls, Richard Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. Heat -- Transmission -- Mathematical models Timber -- Thermal properties Structural engineering -- Safety measures Connections (Mathematics) UCTD Sulon, D. 2025. Heat transfer modelling for timber connections in fire considering uncertainty quantification. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/6e44f2e3-042f-4543-a69d-898f6d59ae48 Thesis (PhD)--Stellenbosch University, 2025 ENGLISH ABSTRACT: Advanced calculation methods, such as Finite Element Methods (FEM), offer powerful tools for analysing structural timber connections exposed to fire. These models typically rely on predicted temperature distributions to assess the degradation of material properties in heated regions of the timber, which, in turn, inform the reduction of structural capacity in the connections. Given this background, this thesis presents both experimental and numerical investigations that contribute towards the understanding of temperature evolution and modelling of timber connections in fire conditions. A series of simple timber connections, including rectangular gaps and dowelled connections with varying levels of fire protection, were tested under unloaded conditions following ISO 834 fire exposure. The objective was to examine how the connection geometry influences temperature evolution within the tested configurations. Two types of South African glue-laminated timber were evaluated, specifically beams produced from pine and eucalyptus. Solid timber specimens were tested as a control group to benchmark the experimental temperature results. Furthermore, the charring rates for each species were determined and compared with the existing South African structural building regulations (SABS, 2003). The results revealed charring rates of 0.97 mm/min for pine and 0.56 mm/min for eucalyptus. Consequently, the results find that the SABS (2003) provide non-conservative charring rate recommendations for pine, while being conservative for eucalyptus. A Heat Transfer Modelling Methodology (HTMM) for timber connections was developed, incorporating a novel parametrization of the thermal properties of timber. This methodology was validated against existing experimental data for timber and timber connections from the literature (Peng, 2010; Audebert et al., 2011). Moreover, a novel approach towards simulating intumescent sealants is presented using loaded timber connection tests from the literature (Barber, 2017a). Key uncertainties were identified within the heat transfer modelling methodology, mainly as a result of the effective thermal properties of timber and the boundary conditions within connection gaps and holes. Towards addressing the uncertainty, a numerical calibration of the thermal properties was undertaken using Bayesian Inversion. A likelihood function was formulated to compare model predictions with experimental temperature data, and this function was employed to estimate the marginal posterior distributions of the parameters which define the effective thermal properties. The calibration process used Markov Chain Monte Carlo (MCMC) simulations which were accelerated by surrogate modelling techniques, specifically a combinations of Polynomial Chaos Expansion and Principal Component Analysis. As a result, calibrated thermal properties for pine glulam and eucalyptus glulam beams were derived. The calibrated properties were applied to simulate the connection configurations tested in the experimental campaign. A comparative analysis with the experimental data highlighted the impact of convective heating within rectangular gaps, identifying that radiative heating alone could not adequately replicate the observed behaviour in the experiments. Based on this comparison, key improvements to the heat transfer modelling methodology are outlined, highlighting the most critical parameters influencing the models and providing recommendations for the boundary conditions. AFRIKAANSE OPSOMMING: Gevorderde berekeningsmetodes, soos beperkte-element metodes, verskaf n doeltreffende manier om strukturele houtlaste se brandveiligheid te ondersoek. Strukturele modelle, wat ontwikkel is deur hierdie metodes te gebruik, maak staat op die verwagte temperatuurverspreiding in die verhitte dele van die las, om die verswakking van die materiaaleienskappe te evalueer. Die verswakking van die materiaaleienskappe word dan weer gebruik om die verminderde kapasiteit van die strukturele las te bepaal. Gegewe hierdie agtergrond, bied hierdie tesis eksperimentele en numeriese ondersoeke aan wat bydra om die temperatuurontwikkeling en modellering van houtlaste in n brand beter te verstaan. n Reeks eenvoudige houtlaste, insluitende reghoekige gleuwe en taplaste, met verskillende vlakke van brandbeskerming, is getoets onder n nie-belaste opstelling wat blootgestel is aan die ISO 834 brandkurwe. Die doel van die toetse was om die invloed van die lasuitleg op die temperatuur-ontwikkeling in al die verskillende tipes laste wat getoets is, te ondersoek. Twee tipes Suid-Afrikaanse gom-gelamineerde hout is ondersoek, spesifiek balke wat gemaak is van dennehout en bloekomhout. Soliede houtmonsters is getoets as n kontrolegroep, wat dan gebruik is om die eksperimentele temperatuur se toetsresultate in konteks te plaas. Verder, is die verkolingstempo van beide houtspesies bepaal en vergelyk met die bestaande Suid-Afrikaanse struktuurbouregulasies (SABS, 2003). Die resultate het n verkolingstempo van 0.97 mm/min vir dennehout en 0.56 mm/min vir bloekomhout gewys. Gevolglik, bevind die resultate dat die SABS (2003) n nie-konserwatiewe verkolingstempo vir dennehout aanbeveel, terwyl die verkolingstempo vir bloekomhout konserwatief hanteer word. n Hitteoordrag modellerings-metodologie vir houtlaste, wat n nuwe parameterisering vir die bepaling van die termiese eienskappe van hout gebruik is, ontwikkel. Die geldigheid van hierdie metodologie is bepaal deur dit te vergelyk met bestaande eksperimentele data vir hout en houtlaste beskikbaar in die literatuur (Peng, 2010; Audebert et al., 2011). Bo en behalwe die metodologie, word n nuut- ontwikkelde manier om n swellende seellaar te simuleer, ook ten toon gestel deur toetsresultate, van houtlaste onder belasting, in die literatuur te gebruik (Barber, 2017). Kritiese onsekerhede is geidentifiseer in die hitteoordrag modellerings-metodologie, hoofsaaklik as gevolg van die effektiewe termiese eienskappe van hout, en die grenstoestande in die lasgleuwe en gate. Om hierdie onsekerhede aan te spreek, is n numeriese kalibrasie van die termiese eienskappe gedoen deur die Bayesiaanse inversie (Bayesian Inversion) te gebruik. n Waarskynlikheidsfunksie is geformuleer om die model temperatuur-voorspellings te vergelyk met die eksperimentele data. Hierdie funksie is toe gebruik om die marginale posterior verspreidings van die veranderlikes wat die effektiewe termiese eienskappe van die hout bepaal, te skat. Die kalibrasieproses het Markov Ketting Monte Carlo simulasies gebruik, wat versnel is deur surrogaatmodeleringstegnieke, in besonder kombinasies van Polinomiese Chaos Uitbreidings en Hoof Komponent Analise. Die uitkoms was gekalibreerde termiese eienskappe vir gom-gelamineerde dennehout- en bloekomhoutbalke. Hierdie gekalibreerde eienskappe is toe gebruik om al die verskillende lasuitlegte wat getoets is tydens die eksperimentele fase van die werk, te simuleer. n Vergelykende analise met die eksperimentele data het die impak van konveksie hitteoordrag binne reghoekige gleuwe beklemtoon deur te bevind dat, radiasie hitte-oordrag alleen, nie die waarnemings wat tydens die eksperimente gemaak is, voldoende kon naboots nie. Gebaseer op hierdie vergelykings kon sleutelverbeterings aan die hitteoordrag modellerings-metodologie voorgestel word. Die mees kritieke veranderlikes wat die modelle beinvloed kon uitgewys word en voorstelle oor die grenstoestande kon bepaal word. Doctoral 2025-06-02T12:58:42Z 2025-06-02T12:58:42Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132284 en Stellenbosch University xxxii, 216 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Heat -- Transmission -- Mathematical models Timber -- Thermal properties Structural engineering -- Safety measures Connections (Mathematics) UCTD Sulon, Darren Anthony Heat transfer modelling for timber connections in fire considering uncertainty quantification |
| title | Heat transfer modelling for timber connections in fire considering uncertainty quantification |
| title_full | Heat transfer modelling for timber connections in fire considering uncertainty quantification |
| title_fullStr | Heat transfer modelling for timber connections in fire considering uncertainty quantification |
| title_full_unstemmed | Heat transfer modelling for timber connections in fire considering uncertainty quantification |
| title_short | Heat transfer modelling for timber connections in fire considering uncertainty quantification |
| title_sort | heat transfer modelling for timber connections in fire considering uncertainty quantification |
| topic | Heat -- Transmission -- Mathematical models Timber -- Thermal properties Structural engineering -- Safety measures Connections (Mathematics) UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132284 |
| work_keys_str_mv | AT sulondarrenanthony heattransfermodellingfortimberconnectionsinfireconsideringuncertaintyquantification |