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Comparison between high strength steel and conventional steel regarding the overall material usage for a composite bridge
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Structural steels are among the most widely used materials in the constructionsector, of which S355 is the steel that is considered being the norm in Europetoday. As the demands on civil engineering structures are increasing today parallelwith the construction sector intending to become a more environmentalfriendly industry, high strength steel (HSS) has become increasingly relevanttoday with the aim of reducing the material usage and facilitate a more sustainableconstruction. HSS is structural steel with a very high yield strength andultimate strength. In this dissertation, structural steels with a yield strengthof 500MPa or above were classified as HSS.In this thesis, the main steel girders of the E4 bridge over the Vapelbäcken,which is a continuous steel-concrete composite highway bridge, were optimizedwith HSS S690 and conventional structural steel S355 in order to investigatehow HSS affects the material usage for the bridge compared to the conventionalsteel. In addition to the above, a cost analysis, modal analysis and a fatigueassessment of bridge were carried out in order to analyse how the mass changedue to HSS affects the material cost of the bridge as well as the bridge’s dynamicproperties and fatigue resistance.The main girders of the bridge were optimized with respect to the ultimatelimit state (ULS). The optimization initiated with a structural analysis of thebridge using the finite element software Abaqus. Design calculations were thenperformed for the girders in accordance with the Eurocodes. Afterwards, thecross-sections of the main girders were optimized. When the optimization wascompleted, a cost analysis, modal analysis and the fatigue assessment wereperformed for the bridge.The optimization showed that HSS significantly reduces the material usagecompared to conventional steel if the optimization takes place with respect tothe ULS. The cost analysis showed that the bridge with optimized main girdersof HSS was the cheapest option, indicating that HSS can be a more economicalalternative than conventional structural steel if the material reduction is largeenough.The large material reduction that HSS entails led to deterioration of the bridge’sother properties. The modal analysis showed that the bridge with optimizedgirders of HSS was had the lowest natural frequency, indicating that the largemass reduction of the bridge due to HSS results in a impairing of the bridge’sdynamic properties since a large mass reduction impairs the stiffness of thestructure which in turn decreases the natural frequency. The fatigue assessmentshowed that the bridge with optimized girders of HSS had the lowestfatigue capacity, which means that the yield strength of the material does nothave an impact on the fatigue capacity and therefore the benefits of HSS cannotbe exploited in cases where fatigue governs the structural design.

Place, publisher, year, edition, pages
2019.
Series
TRITA-ABE-MBT ; 19472
Keywords [en]
High strength steel; Conventional structural steel; Composite bridge; Optimization; Finite element analysis; Cost analysis; Modal analysis; Fatigue assessment
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-254383OAI: oai:DiVA.org:kth-254383DiVA, id: diva2:1331617
Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-10-04

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