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Flexible culverts in sloping terrain: Numerical simulation of soil loading effects
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ViaCon AB, Sweden .ORCID iD: 0000-0002-3030-9231
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Skanska Sweden AB - Major Projects, Sweden .
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.ORCID iD: 0000-0002-5447-2068
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.

Place, publisher, year, edition, pages
2015. Vol. 101, p. 111-124
Keywords [en]
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: urn:nbn:se:kth:diva-171212DOI: 10.1016/j.engstruct.2015.07.004ISI: 000362142200010Scopus ID: 2-s2.0-84937216450OAI: oai:DiVA.org:kth-171212DiVA, id: diva2:842729
Note

QC 20150805

Available from: 2015-07-22 Created: 2015-07-22 Last updated: 2018-11-30Bibliographically approved
In thesis
1. Flexible culverts in sloping terrain: Research advances and application
Open this publication in new window or tab >>Flexible culverts in sloping terrain: Research advances and application
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Although the construction of flexible culverts involves simplicity in comparison to similar concrete structures, the complexity of the beneficial interaction between soil and steel materials requires good understanding for their composite action and performance. Current design methods have certain validity limitations with regard to applicable slopes above the structures. Given the short construction time of flexible culverts, there is an urge to explore the feasibility and the constructability of such as cost-effective structures in sloping terrain, where they may function as an avalanche protection structure for a given road, a culvert under a ski slope, or even as a protection canopy for tunnel entrances.

This report compiles the efforts carried out toward gaining knowledge about the different factors that may affect the behaviour of flexible culverts in sloping environment. The report includes an extended summary of the investigation, which is mainly presented in two appended papers. The study involved numerical simulation of three case studies to investigate their performances with regard to soil loading and avalanche loads as well. The height of cover, surface slope intensity, slope stability, soil support conditions, and avalanche proximity, were studied and discussed.

The study results allowed realizing the susceptibility of flexible culverts to low heights of soil cover when built in sloping terrain, which is reflected in the deformation response and the incremental change in sectional forces, especially the bending moments. It is also found that increasing the depth of soil cover may feasibly improve the structural performance under asymmetrical soil loading and avalanche loads, where it subsequently help in reducing the bending moments in the wall conduit. The presence of a flexible culvert may affect adversely the soil stability in sloping terrain and thus need to be addressed in design. Furthermore, the flexural response of a flexible culvert is directly influenced by the soil support configuration at the downhill side of the structure. In addition, the report also attempts to highlight some general guidelines about the design aspects of flexible culverts in sloping terrain, and seeks to reflect some of the findings on the design methodology for flexible culverts used in Sweden.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. p. viii, 47
Series
TRITA-BKN. Bulletin, ISSN 1103-4270 ; 135
Keywords
Flexible culvert, Soil‒steel composite bridge, Sloping terrain, Swedish design method, Finite element model, Slope stability, Avalanche load, Snowshed
National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-177903 (URN)
Presentation
2015-12-03, M108, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151130

Available from: 2015-11-30 Created: 2015-11-30 Last updated: 2015-11-30Bibliographically approved
2. Soil-Steel Composite Bridges: Research advances and application
Open this publication in new window or tab >>Soil-Steel Composite Bridges: Research advances and application
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
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:nbn:se:kth:diva-239685 (URN)978-91-7873-045-2 (ISBN)
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

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