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Strengthening of a Composite I-girder Bridge by Trusses Introducing Box-Action
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
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0003-1435-0071
2022 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

The increased amount of traffic and the increasingly heavier loads on the road network push the existing infrastructure to its design limit. Bridges, which are an important part of the road network, need to be adopted to the new traffic demands regarding both the load capacity and the fatigue limit state, FLS. Steel-concrete composite bridges, with twin steel I-girders, is a common bridge type in the Nordic countries. These bridges are often designed using beam models, assuming that the concrete deck is a statically determinate structure supported on the two steel girders in the transversal direction. This assumption implies that the most loaded girder can sometimes be subjected to even more than 100% of an eccentric load, e.g., the traffic loads in the design codes. If the girders are strengthened to be able to share the eccentric loads more equally, it would have a significant impact on the load capacity, especially for the fatigue limit state. By introducing horizontal trusses between the bottom flanges of the girders, making the cross-section act more like a box-girder, the torsional stiffness will increase so that the girders will share the eccentric loads more equally. The bracing system of the trusses can be designed in different shapes, each of them with pros and cons for the existing bridge structure. In this paper, the effects from different shapes of the bracing are evaluated of a single span I-girder composite bridge. The increased torsional stiffness and the change of the internal shear flow will increase the load capacity of the steel girders.

Place, publisher, year, edition, pages
2022.
Keywords [en]
bridge, steel-concrete composite, I-girder, case study, horizontal trusses, torsional stiffness, strengthening, composite bridges
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-96211OAI: oai:DiVA.org:ltu-96211DiVA, id: diva2:1745136
Conference
10th International symposium on steel bridges – for A Green Planet, September 20 - 22, 2022 Istanbul, Turkey
Available from: 2023-03-22 Created: 2023-03-22 Last updated: 2023-09-05
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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