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Gång- och cykelbro i rostfritt duplexstål: En utredning genom livscykelanalys, kostnadsanalys och konstruktionstekniska beräkningar

Frantzich, Matilda LU (2019) FMIM01 20191
Environmental and Energy Systems Studies
Abstract (Swedish)
Rostfritt duplexstål är ett konstruktionsmaterial som skulle kunna tänkas vara konkurrenskraftigt i förhållande till konventionella material inom brobyggnad med tanke på dess höga hållfasthet, marginella underhållsbehov och möjlighet till återvinning. Hittills har det dock inte använts i någon större utsträckning inom brobyggnad framför allt på grund av dess högre kostnad i förhållande till traditionellt kolstål. I denna studie analyseras en gång- och cykelbro av fackverkstyp tillverkad av rostfri duplexstålplåt utifrån tre perspektiv: miljöpåverkan, ekonomiska kostnader och konstruktionsteknisk utformning. Syftet är dels att utreda materialets potential inom brobyggnad dels att undersöka den aktuella broutformningens möjligheter och... (More)
Rostfritt duplexstål är ett konstruktionsmaterial som skulle kunna tänkas vara konkurrenskraftigt i förhållande till konventionella material inom brobyggnad med tanke på dess höga hållfasthet, marginella underhållsbehov och möjlighet till återvinning. Hittills har det dock inte använts i någon större utsträckning inom brobyggnad framför allt på grund av dess högre kostnad i förhållande till traditionellt kolstål. I denna studie analyseras en gång- och cykelbro av fackverkstyp tillverkad av rostfri duplexstålplåt utifrån tre perspektiv: miljöpåverkan, ekonomiska kostnader och konstruktionsteknisk utformning. Syftet är dels att utreda materialets potential inom brobyggnad dels att undersöka den aktuella broutformningens möjligheter och begränsningar med hänsyn till dimensioner och detaljutformning. För att göra en samlad bedömning av bron vägs resultat från livscykelanalys och kostnadsanalys samman i en samhällsekonomisk bedömning.

Resultatet visar på att det är möjligt att uppnå längre spännvidder än 20 m med tunna stålplåtar men att bucklingsfenomen är kritiskt för bärförmågan och måste beaktas noggrant. Det är dock möjligt att med mindre förändringar av utformningen av knutpunkterna i fackverket både öka styvheten i tvärled och reducera spänningsnivåerna i områden med lokalt höga värden.

Livscykelanalysen visade i sin tur att det rostfria duplexstålet ger upphov till mindre utsläpp av växthusgaser än traditionellt konstruktionsstål under förutsättning att dess höga hållfasthet kan leda till en reduktion av mängden använt material. Produktion av rostfritt stål från jungfruliga råvaror ger dock upphov till större växthusgasutsläpp per ton än kolstål. Om stålet genom framtida återvinning kan ersätta nyproducerat material kan den rostfria bron få en miljöpåverkan som är jämförbar med en träbro, dock under antagandet att den senare har kortare teknisk livslängd.

Kostnadsanalysen visade att den rostfria bron är likvärdig med motsvarande kolstålbro sett till kostnaderna över hela livslängden men att träbron får betydligt högre kostnad på grund av stort underhållsbehov. Inkluderas också kostnader som uppstår på grund av störningar av trafiken vid underhållsåtgärderna i den samhällsekonomiska bedömningen faller dock den rostfria bron ut som det bästa alternativet. Utfallet av kostnadsanalysen är starkt beroende av vilken kalkylränta som tillämpas. Miljökostnader utgör endast en liten del av den samhällsekonomiska kostnaden, ca 6% för den rostfria bron om Trafikverkets rekommenderade värderingsmetod används. (Less)
Abstract
Duplex stainless steel is a construction material that could possibly prove competitive in relation to conventional materials in bridge design, given its high strength, marginal maintenance needs and the possibility of recycling. To date, however, it has not been used to any great extent in bridge constructions, mainly because of its higher cost in relation to traditional carbon steel. In this study, a pedestrian bridge of truss type made from duplex stainless steel sheet is analyzed from three perspectives: environmental impact, economic costs and structural design. The purpose is to investigate the potential of the steel type in bridge design and to examine the possibilities and limitations of the current bridge design with respect to... (More)
Duplex stainless steel is a construction material that could possibly prove competitive in relation to conventional materials in bridge design, given its high strength, marginal maintenance needs and the possibility of recycling. To date, however, it has not been used to any great extent in bridge constructions, mainly because of its higher cost in relation to traditional carbon steel. In this study, a pedestrian bridge of truss type made from duplex stainless steel sheet is analyzed from three perspectives: environmental impact, economic costs and structural design. The purpose is to investigate the potential of the steel type in bridge design and to examine the possibilities and limitations of the current bridge design with respect to dimensions and detail design. To make an overall assessment of the bridge, results from life cycle analysis and cost analysis are weighted together in a socio-economic assessment.

The result shows that it is possible to achieve longer span width than 20 m with thin steel plates, but that buckling phenomena is critical to the bearing capacity and must be carefully considered. However, it is possible to increase the stiffness in the transverse direction and reduce the stress levels in areas with locally high values with minor design changes of the nodes of the truss structure.

The life cycle analysis, in turn, showed that the duplex stainless steel gives rise to less climate impact than traditional structural steel, provided that its high strength can lead to a reduction in the amount of material used. However, the production of stainless steel from virgin raw materials gives rise to larger greenhouse gas emissions per tonne compared to carbon steel. If the steel through future recycling can replace newly produced material, the stainless steel bridge can have an environmental impact that is comparable to a bridge with wood as primary material assuming the latter has a shorter technical service life.

The cost analysis showed that the stainless steel bridge is equivalent to the corresponding carbon steel bridge with respect to cost over the entire service life, but that the wooden bridge has a considerably higher cost due to large maintenance needs. However, if costs that arise from traffic disruptions connected to maintenance related activities are included, the stainless steel bridge can be considered as the best alternative from a socio-economic point of view. The outcome of the cost analysis is strongly dependent on the discount rate applied. Environmental costs represent only a small part of the total socio-economic cost, about 6% for the stainless-steel bridge if the Swedish Transport Administration's recommended valuation method is used. (Less)
Please use this url to cite or link to this publication:
author
Frantzich, Matilda LU
supervisor
organization
alternative title
Pedestrian bridge in duplex stainless steel: A study through life cycle analysis, socio-economic assessment and structural analysis
course
FMIM01 20191
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Brobyggnad, rostfritt duplexstål, livscykelanalys, miljöpåverkan, samhällsekonomisk analys, finit elementmodellering
report number
ISRN LUTFD2/TFEM—19/5145—SE + (1-139)
ISSN
1102-3651
language
Swedish
id
8991393
date added to LUP
2019-08-12 12:49:35
date last changed
2019-08-12 12:49:35
@misc{8991393,
  abstract     = {Duplex stainless steel is a construction material that could possibly prove competitive in relation to conventional materials in bridge design, given its high strength, marginal maintenance needs and the possibility of recycling. To date, however, it has not been used to any great extent in bridge constructions, mainly because of its higher cost in relation to traditional carbon steel. In this study, a pedestrian bridge of truss type made from duplex stainless steel sheet is analyzed from three perspectives: environmental impact, economic costs and structural design. The purpose is to investigate the potential of the steel type in bridge design and to examine the possibilities and limitations of the current bridge design with respect to dimensions and detail design. To make an overall assessment of the bridge, results from life cycle analysis and cost analysis are weighted together in a socio-economic assessment. 
 
The result shows that it is possible to achieve longer span width than 20 m with thin steel plates, but that buckling phenomena is critical to the bearing capacity and must be carefully considered. However, it is possible to increase the stiffness in the transverse direction and reduce the stress levels in areas with locally high values with minor design changes of the nodes of the truss structure. 
 
The life cycle analysis, in turn, showed that the duplex stainless steel gives rise to less climate impact than traditional structural steel, provided that its high strength can lead to a reduction in the amount of material used. However, the production of stainless steel from virgin raw materials gives rise to larger greenhouse gas emissions per tonne compared to carbon steel. If the steel through future recycling can replace newly produced material, the stainless steel bridge can have an environmental impact that is comparable to a bridge with wood as primary material assuming the latter has a shorter technical service life. 
 
The cost analysis showed that the stainless steel bridge is equivalent to the corresponding carbon steel bridge with respect to cost over the entire service life, but that the wooden bridge has a considerably higher cost due to large maintenance needs. However, if costs that arise from traffic disruptions connected to maintenance related activities are included, the stainless steel bridge can be considered as the best alternative from a socio-economic point of view. The outcome of the cost analysis is strongly dependent on the discount rate applied. Environmental costs represent only a small part of the total socio-economic cost, about 6% for the stainless-steel bridge if the Swedish Transport Administration's recommended valuation method is used.},
  author       = {Frantzich, Matilda},
  issn         = {1102-3651},
  keyword      = {Brobyggnad,rostfritt duplexstål,livscykelanalys,miljöpåverkan,samhällsekonomisk analys,finit elementmodellering},
  language     = {swe},
  note         = {Student Paper},
  title        = {Gång- och cykelbro i rostfritt duplexstål: En utredning genom livscykelanalys, kostnadsanalys och konstruktionstekniska beräkningar},
  year         = {2019},
}