Change search
ReferencesLink to record
Permanent link

Direct link
Evaluation of the Load Carrying Capacity of a Steel Truss Railway Bridge: Testing, Theory and Evaluation
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

A good deal of resources has been invested in building and maintaining existing infrastructure.Many structures are now becoming old and do not meet the requirements of an increasingtraffic load, or are reaching the end of their lifecycle. It is not possible or sustainable to replaceall those structures that have been judged to be obsolete or nearly obsolete. However, in manycases, their specified load carrying capacities are understated, so there is an urgent need toobtain more robust knowledge of their true status. In the design of new structures, a numberof assumptions relating to loading and structural behaviour have to be made, a number that canbe reduced by finding out more about the actual behaviour of the structure.

This licentiate thesis describes the structural behaviour of existing unballasted open steel trussrailway bridges in general and methods for assessment in particular, with the aim of keepingthese structures in service for longer.

An extensive program, divided into three phases of experimental studies, was carried out toincrease the understanding of existing unballasted steel truss railway bridges.

Phase I consisted of instrumentation and monitoring of a 60 year-old railway bridge (ÅbyBridge) while it was still in service. A description of the object and the monitoring in thisphase of measurements is presented in Chapter 3 with some results and analysis in Chapter 4.Some of the findings from Phase I are described in Paper A, from which it was concluded thatthe stringer beams were subjected to large stresses originating from torsion and out-of-planebending. These effects are not normally considered yet may have significant consequences inrelation to fatigue.

In Phase II, the former bridge over the Åby River was replaced and put beside the railwaytracks, where the instrumentation from Phase I was extended. The bridge was statically testedin 18 pre-defined load series before reaching failure. Phase II is described in Chapter 3 andsummarized in Paper B. It was found that the bridge could withstand loading corresponding tofour times the highest permitted axle-loading, or twice the design load for new bridges, beforeexhibiting an obvious non-linear behaviour with regard to vertical displacement in the midspan.The peak load was achieved at loading approximately 50% higher than the initial nonlinearbehaviour, where lateral buckling of the top chord limited the structure from carryingmore load. The failure can be concluded as being redundant without brittle failure of any ofthe connections.

In Phase III, a different bridge was fitted with instrumentation and monitored while subjectedto live loading: the bridge over the river Rautasjokk. The Rautasjokk Bridge was constructedfive years later than the Åby Bridge, using the same drawings thus making it theoreticallyidentical in terms of geometry and material. It is situated along the “Ore line”, meaning that itis subjected to higher loads compared to the Åby Bridge which was located along the “Mainline”. The program for measurements originated from a code-based assessment which ruled thebridge unsafe to use with regard to fatigue of the stringers due to the gusset plates welded tothe top flange of the stringers. Paper C describes the measurement of local fatigue strains (hotspot)and comparison with nominal strains. In that paper, it was concluded that the hot-spotapproach was only favourable for one out of three studied positions, with regard to fatiguelifespan.

This thesis ends with conclusions and suggestions for further research.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2016. , 139 p.
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Civil Engineering
Research subject
Structural Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-60029ISBN: 978-91-7583-739-0ISBN: 978-91-7583-740-6 (pdf)OAI: oai:DiVA.org:ltu-60029DiVA: diva2:1040790
Presentation
2016-12-15, F1031, Luleå tekniska universitet, Luleå, 10:00
Opponent
Available from: 2016-10-31 Created: 2016-10-28 Last updated: 2016-11-25Bibliographically approved

Open Access in DiVA

fulltext(22310 kB)19 downloads
File information
File name FULLTEXT01.pdfFile size 22310 kBChecksum SHA-512
e93a6325f8654e6d21376f8e8ae49a982aac1620f99cabf87827a04af3e62ed00172cbc208ae511c0aa4415173b6e5bc1151cdff1789c92703aa7f70de5fdf3b
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Häggström, Jens
By organisation
Department of Civil, Environmental and Natural Resources Engineering
Civil Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 19 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 154 hits
ReferencesLink to record
Permanent link

Direct link