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Optimizing the steel girders in a high strength steel composite bridge
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.ORCID iD: 0000-0002-3699-0814
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. KTH Royal Inst Technol, Div Struct Engn & Bridges, S-10044 Stockholm, Sweden..ORCID iD: 0000-0002-2833-4585
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.ORCID iD: 0000-0002-5447-2068
2020 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 221, article id 110981Article in journal (Refereed) Published
Abstract [en]

The use of high strength steel has the potential to reduce the amount of steel used in bridges and thereby, facilitate a more sustainable construction. In this study, an optimization of a composite steel and concrete bridge is presented. The study aimed at identifying the potential benefits of using high strength steel, compared to conventional steel, in terms of weight, material cost and environmental impact. The optimization routine followed what is outlined in the Eurocode and satisfied both ultimate and serviceability limit state conditions, with exception of fatigue. To study the influence of fatigue a separate verification was performed on the solutions found from the optimization. The study showed that substantial savings in weight, environmental impact and material cost could be made by implementing high strength steel. However, when the fatigue verification according to Eurocode was considered, the potential benefits of using steels of higher grade vanished completely.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD , 2020. Vol. 221, article id 110981
Keywords [en]
High strength steel, Composite steel and concrete bridge, Optimization, Hybrid girder, Fatigue
National Category
Infrastructure Engineering
Identifiers
URN: urn:nbn:se:kth:diva-281127DOI: 10.1016/j.engstruct.2020.110981ISI: 000561737400003Scopus ID: 2-s2.0-85087411636OAI: oai:DiVA.org:kth-281127DiVA, id: diva2:1467790
Note

QC 20200916

Available from: 2020-09-16 Created: 2020-09-16 Last updated: 2022-06-25Bibliographically approved
In thesis
1. Fatigue of steel bridges: New structural details and the implementation of high strength steel
Open this publication in new window or tab >>Fatigue of steel bridges: New structural details and the implementation of high strength steel
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of high strength steel has the potential to reduce the amount of steel used in bridge structures and thereby facilitate a more sustainable construction. The amount of steel and what steel grade that can be used in bridge structures and other cyclic loaded structures are often limited by a material degradation process called fatigue. The fatigue resistance of steel bridges is to a large extent depending on the design of structural details and connections. The design engineer is limited by the selection of a few pre-existing structural details with rather poor fatigue strength to choose from when designing steel bridges. Therefore, he/she is often forced to increase the overall dimensions of the structure to cope with the design requirements of fatigue.This doctoral thesis aims at increasing the fatigue resistance of fatigue prone structural details and connections by implementing new structural solutions to the already existing details given in the design standards. A typical fatigue prone detail is the vertical stiffener at an intermediate cross-beam, which will be in focus. By improving the fatigue resistance, less steel material will be required for the con-struction of new steel bridges and composite bridges of steel and concrete. It is shown in this thesis and the appended papers that the use of high strength steel for bridge structures can considerably reduce the amount of steel used, the cost of the steel material, and the harmful emissions. However, this is only true if the fatigue strength of critical details can be improved. This is shown through a survey of existing bridge structures and an optimisation of a steel and concrete composite bridge.Furthermore, a few new structural details are proposed and a few already existing solutions are highlighted that have the potential to improve the fatigue strength. The most promising structural detail could potentially increase the fatigue strength by 25 %. This is shown through numerical analyses using linear elastic fracture me-chanical models. However, the new structural details should be verified through fatigue experiments as a final step to determine their fatigue strength.

Abstract [sv]

Genom användandet av höghållfast stål kan en mindre mängd material användas som i sin tur leder till ett mer hållbart byggande. Mängden stål och vilken stålkvalité som kan användas vid byggandet av stålbroar och andra cykliskt belastade konstruktioner avgörs ofta av nedbrytningsprocessen utmattning. Utmattningskapaciteten hos stålbroar är till stor del beroende av brons anslutningsdetaljer. Brokonstruktören har vid designstadiet ett begränsat antal beprövade anslutningsdetaljer att välja bland – vilka ofta har relativt låg utmattningskapacitet – och konstruktören är därmed ofta tvungen att öka konstruktionens dimensioner för att klara av kraven gällande utmattning. Den här avhandlingen har till syfte att förbättra utmattningkapaciteten för utmattningsbenägna anslutningsdetaljer i stål genom att införa nya anslutningsdetaljer bland de redan existerande detaljerna som finns i de olika standarderna. En utmattningskritisk detalj som ligger i fokus är anslutningen mellan livavstyvningen och tvärförbanden hos stålbalkbroar. Genom att förbättra utmattningskapaciteten så kan en mindre mängd stålmaterial användas vid byggandet av stålbroar och samverkansbroar i betong och stål. I denna avhandlingen kunde det påvisas att höghållfast stål för broar kan sänka mängden stålmaterial, stålkostnaden och koldioxidutsläppen. Dock så gäller detta enbart om utmattningskapaciteten för kritiska anslutningsdetaljer kan ökas avsevärt. Detta visas genom en kartläggning av existerande broar och genom en optimiering av en samverkansbro i stål och betong. Dessutom, så presenteras ett antal nya anslutningsdetaljer och ett fåtal redan existerande lösningar uppmärksammas som har potential att förbättra utmattningskapaciteten. Den mest lovande anslutningsdetaljen kan potentiellt öka utmattning-shållfastheten med 25 %. Detta visas genom numeriska analyser med användning av linjärelastiska brottmekaniska modeller. Detta kräver dock verifiering genom experimentella studier för att fastställa deras kapacitet.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022. p. 42
Series
TRITA-ABE-DLT ; 223
Keywords
high strength steel, fatigue, steel bridges, steel and concrete composite bridges, new structural details, linear elastic fracture mechanics, effective notch stress method, nominal stress method
National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering, Structural Engineering and Bridges
Identifiers
urn:nbn:se:kth:diva-309186 (URN)978-91-8040-131-9 (ISBN)
Public defence
2022-03-25, B3, Brinellvägen 23, Även digitalt via zoom:https://kth-se.zoom.us/j/63293304009, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Transport Administration, 2016-010
Note

QC 2022-03-03

Available from: 2022-03-03 Created: 2022-02-23 Last updated: 2022-06-25Bibliographically approved

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Skoglund, OskarLeander, JohnKaroumi, Raid

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