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Horizontal bracing between bottom flanges in composite I-girder bridges – A state of the art review
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0002-9627-4713
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0002-8353-9225
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(English)In: Practice Periodical on Structural Design and Construction, ISSN 1084-0680, E-ISSN 1943-5576Article in journal (Other academic) Submitted
Abstract [en]

The tradition in how steel bridges are designed and built varies around the globe. These traditions can be based upon the accessibility to materials and products, but also the topographical conditions for the bridge locations. In the Nordic countries the most common type for the superstructure of steel girder bridges, is the welded steel girder. In contrary, steel girder bridges in many other European countries are more commonly built with rolled steel sections. Variations can also be seen in how details are designed, as on-site joints were a bolted or a welded connection are used. The difference in the use of a horizontal bracing between the main girders, often designed as a wind bracing, in different countries are not well known. The bracing is often used to distribute horizontal loads as wind and is then called a wind bracing. The bracing will also, and this is used in the design in some countries, distribute eccentric vertical loads due to its increase of the torsional stiffness of the structure.

This paper investigates the premise that the use of horizontal bracing between the bottom flanges of new I-girder bridges results in a cross-section that behaves similarly to a steel box-beam where the vertical webs share more equally in the applied loads. This concept lowers the beam stresses and is particularly beneficial for fatigue evaluation caused by eccentric loads. The concept is exemplified by in-service bridges in Finland, Guatemala, France, and the US. The potential to use horizontal bracing as a strengthening technique in existing steel two-girder composite bridges is also discussed.

Keywords [en]
bridge, composite bridge, horizontal trusses, horizontal bracing, lateral bracing, strengthening, torsional stiffness
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-96209OAI: oai:DiVA.org:ltu-96209DiVA, id: diva2:1745125
Available from: 2023-03-22 Created: 2023-03-22 Last updated: 2024-04-12
In thesis
1. I-girder Composite Bridges with Lateral Bracing: Improved load distribution
Open this publication in new window or tab >>I-girder Composite Bridges with Lateral Bracing: Improved load distribution
2023 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the subject of lateral bracing between the bottom flanges of I-girder composite bridges. The focus is on the impact of adding lateral bracing on existing bridges, as well as on new bridges. Experience and knowledge from bridge projects around the world are investigated and implemented in the evaluation of the research subject.

Many existing bridges are in need of being strengthened or replaced, due to the increased traffic volume and heavier traffic loads. Different approaches can be used to prolong the lifetime of existing bridges. The approach is different depending on the cause, but for increasing the lifetime regarding fatigue some of the most suitable options are described in this thesis. A proposed concept is presented, in this thesis, along with some research questions to be answered.

The use of lateral bracings in composite bridges varies between different parts of the world. In one country it can be a requirement/common praxis for long span composite bridges with two I-girders, in other countries there are no requirements of using them. Some parts of these regulations and requirements can be traced back to the tradition in both manufacturing and construction of this type of bridges. This thesis investigates how lateral bracing is used around the world to distribute eccentric loads between primary longitudinal structural members, provide resistance to lateral loads, and to permit an existing two-girder structural system to be retrofitted to behave similarly to an often more expensive closed steel box girder.

Furthermore, several case studies have been conducted to investigate the impact on the structural behavior of composite bridges where a lateral bracing is implemented in the structure. The results from these case studies are presented in the thesis and show the advantages of the quasi-box section for which the lateral bracing is closing the composite cross section. By making the I-girder composite cross section acting more like a box-section, the distribution of eccentric loads between the girders is improved. The impact on longitudinal stresses from traffic loads and the additional effects on internal sectional parts are also evaluated and discussed.

Furthermore, proposals of the connection design for lateral bracings in existing bridges are suggested. Finally, conclusions from the results are stated.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2023
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
assessment, bridge, composite bridge, steel-concrete composite, I-girder, case study, horizontal trusses, lateral bracing, rehabilitation, strengthening, torsional stiffness, upgrading
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-96212 (URN)978-91-8048-286-8 (ISBN)978-91-8048-287-5 (ISBN)
Presentation
2023-05-12, F1031, Luleå tekniska universitet, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2023-03-22 Created: 2023-03-22 Last updated: 2023-12-18Bibliographically approved

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Vestman, VictorCollin, PeterHällmark, Robert

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