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Soil-Steel Composite Bridges: Research advances and application
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.ORCID iD: 0000-0002-3030-9231
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soil-steel composite bridges are considered competitive structures being an economical alternative to similar span concrete bridges. This frequently stimulates practitioners to push their design limits and expand the different areas of application including their performance in sloping terrain. This also implies that most design methods are continuously being developed to address new market challenges and at the same time to seek for better design and construction.

This thesis compiles the recent research efforts to advance the knowledge on the structural performance of soil-steel composite bridges (SSCB). The first part of the thesis investigates the performance of SSCB in sloping terrain, where numerical simulations are used to predict the behaviour of three case studies. This includes structural response under sloped soils and also avalanche loads (Paper I and Paper II). The research enabled to realize the importance of soil configuration around the wall conduit and its influence on the structural response. While the presence of surface slopes emphasizes the susceptibility of SSCB with low depths of soil cover, higher covers may help in reducing the influence of steep slopes and avalanche loads. It was also found that the downhill soil configuration has substantial effects on the flexural response. The findings of the study were also used to provide methods for preliminary estimates of normal forces under sloped soils and avalanches.

To better understand the load bearing capacity of SSCB, the second part of this thesis deals with the behaviour of large-span structures. It includes the use of finite element method simulations (FEM) for the analysis and the prediction of a previous full-scale loading-to-failure test (Paper III). The study also presents response predictions on the ultimate capacity of a large-span structure pertaining to its ongoing preparation for a full-scale field test (Paper IV). The thesis also includes discussions and possible refinements on current design equations concerning buckling calculations and live load effects. The results of the study have allowed to realize the major role of the soil load effects on the subsequent formation of yield areas and failure loads. It is found that the load position has a direct influence on the ultimate capacity especially for large-span structures. The study also highlighted the variations in the distribution of the live load sectional forces in both the circumferential and the transverse directions of the corrugations. Furthermore, possible refinements are proposed on current design equations of which are believed closely relevant on the path for the design development of large-span structures.

Abstract [sv]

Rörbroar är ofta ett ekonomiskt alternativ till betongbroar. Detta har lett till att utvecklingen har drivits mot allt större spännvidder och också att de provas i nya tillämpningsområden. Ett sådant område är användning i sluttande terräng, ofta som snörasskydd för vägar och järnvägar. Detta innebär också att de dimensioneringsmetoderna kontinuerligt behöver utvecklas för att möta dessa behov. Samtidigt är det naturligtvis angeläget att söka efter förbättrade dimension­erings- och byggmetoder.

I den första delen av avhandlingen undersöks rörbroars funktionssätt i lutande terräng. Nume­riska simuleringar används för tre fallstudier. Såväl effekten av den lutande terrängen som belastning med lavinlaster studerades. Studierna visade att effekten av lutande terräng är mer uttalad vid låg överfyllnad. Effekten av att öka överfyllnaden studerades därför och befanns positiv. Studien visade också betydelsen av att utforma motfyllningen på nedsidan av rörbron på ett ändamålsenligt sätt. En metodik för att uppskatta normalkraften i rörbron vid lutande terräng utvecklades som del av studierna.

I den andra delen av avhandlingen behandlas rörbroar med stora spännvidder. Särskilt studeras det sätt som de bär de laster de belastas med upp till en sådan lastnivå att brott inträffar. Detta har gjorts med hjälp av FEM-simuleringar (FEM = Finita Element Metoden) av ett tidigare ut­fört försök i full skala som bland annat omfattade belastning till brott. Simuleringsresultaten, där bland annat fördelningen av snittkrafterna vid belastning med trafiklast redovisas i såväl längs- som tvärriktningen, visar betydelsen av att inkludera de snittkrafter som uppstår på grund av kringfyllningen när den maximala kapaciteten ska bestämmas. Studierna visade också att lastläget påverkar bärförmågan, särskilt vid stora spännvidder. Resultatet från denna simulering har använts för att simulera uppträdandet hos en stor rörbro som del av förberedelserna för ett kommande försök i full skala. Avslutningsvis lämnas också rekommendationer avseende för­slag till justeringar av några av de ekvationer som ingår i den svenska dimensionerings­metoden (SDM).

Place, publisher, year, edition, pages
Stockholm: Kungliga tekniska högskolan, 2019. , p. 109
Series
TRITA-ABE-DLT ; 1842
Keywords [en]
Flexible culvert, Soil‒steel composite bridge, Sloping terrain, Swedish design method, Finite element model, Ultimate capacity, Avalanche load, Failure load, Low soil cover, Failure mechanism, Long-span
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-239685ISBN: 978-91-7873-045-2 (print)OAI: oai:DiVA.org:kth-239685DiVA, id: diva2:1267046
Public defence
2019-01-18, Kollegiesalen, Brinellvägen 8, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20181130

Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2018-11-30Bibliographically approved
List of papers
1. Flexible culverts in sloping terrain: Numerical simulation of soil loading effects
Open this publication in new window or tab >>Flexible culverts in sloping terrain: Numerical simulation of soil loading effects
2015 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 101, p. 111-124Article in journal (Refereed) Published
Abstract [en]

This paper investigates the performance of flexible culverts – often referred to as soil–steel composite bridges (SSCB) – when constructed in sloping topography. A number of 2D finite element models were created to simulate three case studies compromising two pipe arches and one high profile arch. The models were generated to investigate the effect of different surface slopes for different depths of soil cover. The aim was to understand and perceive the change of sectional forces in the structure with respect to slope increase under different soil covers. In addition, the effect of structure presence in the soil was also investigated in terms of soil stability. The results enable to realize the susceptibility of such structures to low heights of soil cover when built in sloping environment, which is seen in the incremental change in displacements and sectional forces, specially the bending moments. It is also found that the geometrical aspects of the profile shapes have more pronounced effect on their performance when introducing steeper slopes. The safety factor of soil stability is found to decrease when introducing such structures in the soil.

Keywords
Soil–steel composite bridge, Flexible culvert, Swedish design method, Sloping terrain, Slope stability, Finite element model
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-171212 (URN)10.1016/j.engstruct.2015.07.004 (DOI)000362142200010 ()2-s2.0-84937216450 (Scopus ID)
Note

QC 20150805

Available from: 2015-07-22 Created: 2015-07-22 Last updated: 2018-11-30Bibliographically approved
2. Flexible culverts in sloping terrain: Numerical simulation of avalanche load effects
Open this publication in new window or tab >>Flexible culverts in sloping terrain: Numerical simulation of avalanche load effects
2016 (English)In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 124, p. 95-109Article in journal (Refereed) Published
Abstract [en]

Avalanche protection concrete structures are expensive and their construction period is often influenced by the climatological conditions at site, which could result in prolonging the erection process and increase its associated costs. Given the short construction time of flexible culverts, such structures can be a cost-effective alternative to traditional protective measures. This article investigates the performance of flexible culverts - often referred to as soil-steel composite bridges (SSCB) - when constructed in sloping topography under avalanche loads. A number of 2D finite element models were created to simulate two case studies composed of a pipe arch and a high-profile arch. The models were generated to investigate the effect of soil cover depth, the avalanche proximity, and the change in soil support conditions around the conduit. The aim was to perceive and understand the changes in deformations and sectional forces under defined avalanche loads. The results enable to realise the effect of shallow soil covers in the pronounced change in bending moments due to avalanches. The proximity of avalanche deviation point has a great influence on the structural performance, though increasing the soil cover depth could considerably help in reducing the bending moments resulting from avalanches. It is also found that the downhill soil support configuration has a substantial effect on the flexural response of the structure.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Flexible culvert, Soil-steel composite bridge, Sloping terrain, Finite element model, Avalanche load, Snowshed
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-184521 (URN)10.1016/j.coldregions.2016.01.003 (DOI)000371903000009 ()2-s2.0-84956901137 (Scopus ID)
Note

QC 20160407

Available from: 2016-04-07 Created: 2016-04-01 Last updated: 2018-11-30Bibliographically approved
3. FEM simulation of a full-scale loading-to-failure test of a corrugated steel culvert
Open this publication in new window or tab >>FEM simulation of a full-scale loading-to-failure test of a corrugated steel culvert
2018 (English)In: Steel and composite structures, ISSN 1229-9367, E-ISSN 1598-6233, Vol. 27, no 2, p. 217-227Article in journal (Refereed) Published
Abstract [en]

This paper utilizes 3D FEM to provide deeper insights about the structural behaviour of a 6.1 m span steel culvert, which was previously tested under extreme loading. The effect of different input parameters pertaining to the backfill soil has been investigated, where the structural response is compared to field measurements. The interface choice between the steel and soil materials was also studied. The results enabled to realize the major influence of the friction angle on the load effects. Moreover, the analyses showed some differences concerning the estimation of failure load, whereas reasons beyond this outcome were arguably presented and discussed.

Place, publisher, year, edition, pages
Korea: , 2018
Keywords
flexible culvert, soil-steel composite bridge, corrugated steel, finite element model, ultimate limit state, failure test
National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-226688 (URN)10.12989/scs.2018.27.2.217 (DOI)000430652600008 ()2-s2.0-85049387239 (Scopus ID)
Note

QC 20180514

Available from: 2018-04-25 Created: 2018-04-25 Last updated: 2018-11-30Bibliographically approved
4. On predicting the ultimate capacity of a large-span soil-steel composite bridge
Open this publication in new window or tab >>On predicting the ultimate capacity of a large-span soil-steel composite bridge
(English)Manuscript (preprint) (Other academic)
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-239692 (URN)
Note

QC 20181206

Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2018-12-06Bibliographically approved

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