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Development of design curves for preliminary dynamic assessment of railway bridges to higher speeds
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.ORCID iD: 0000-0002-5447-2068
(English)In: The International Journal of Railway Technology, ISSN 2049-5358Article in journal (Refereed) Accepted
Abstract [en]

Resonance vibrations of railway bridges have become an important design issue during the last decade due to the development of new high–speed lines. From a designers point of view, this often requires that the bridge is analysed with a finite element software, resulting in long runtimes. The present paper presents design curves to calculate the maximum acceleration, displacement and angular rotation in multi-span bridges, during passages of high-speed trains. The design curves can preferably be used for conceptual design or to evaluate an existing network of bridges. Two numerical examples are included to validate the method and to show possible applications

National Category
Infrastructure Engineering
Identifiers
URN: urn:nbn:se:kth:diva-122435OAI: oai:DiVA.org:kth-122435DiVA: diva2:622347
Note

QS 2013

Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2017-02-12Bibliographically approved
In thesis
1. Simplified dynamic analysis of railway bridges under high-speed trains
Open this publication in new window or tab >>Simplified dynamic analysis of railway bridges under high-speed trains
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The world-wide development of new high-speed rail lines has led to more stringent design requirements for railway bridges. This is mainly due to the fact that a train at high speeds can cause resonance in the bridge superstructure.  In order to avoid problems of this kind, it has become essential to perform dynamic simulations, which are usually carried out in a time consuming finite element program. The main reason for not using an analytical solution is that this type of solution only exists for simple bridges, e.g., simply supported bridges.

The aim of this thesis, is therefore the development of a simplified analytical model for preliminary dynamic analyses of railway bridges. The model is then used in several studies, both parametric and probabilistic ones, to determine the dynamic response of various railway bridges under moving loads. Special attention is paid to acceleration levels in the bridge superstructure, because previous studies have shown that these are often decisive. In the design, both the model and the numerical simulations can be used with considerable effectiveness to help engineers to define their structural systems.

All bridges, throughout this thesis, have been modelled with elastically supported multi-span Bernoulli-Euler beams. The amount of dissipated energy is modelled using modal damping. The train load is modelled by concentrated loads, which implies that the vehicle-bridge interaction is not considered. A model with these characteristics can be used to analyse simply supported concrete bridges as well as multi-span steel bridges. Another advantage of the proposed method is that the solution is exact, because the equation of motion has been solved using a Laplace transform. A lot of effort has been made to have a model both as simple as possible and flexible enough to be able to study a wide variety of structures.

The results of the case studies have shown that concrete bridges are more suitable than steel and composite bridges for use in the new high-speed lines. The simulations have also shown that short-span railway bridges have problems in meeting the design requirements. This confirms the high acceleration levels that were recorded in France, just after the inauguration of the new high-speed line between Lyon and Paris, on several short-span bridges. Furthermore, it was found that a multi-span bridge has a reduction in its dynamic response of up to 60 % compared to a similar simply supported bridge.

Abstract [sv]

Utbyggnaden av nya höghastighetsbanor i världen har resulterat i striktare krav vid dimensionering av järnvägsbroar. Orsaken är främst att tåg vid höga hastigheter kan orsaka resonans i brons överbyggnad. För att kontrollera dessa effekter krävs omfattande dynamiska simuleringar, vilket ofta utförs med tidskrävande FE-analyser. Med analytiska metoder kan beräkningstiden minskas dramatiskt, dessa är dock ofta begränsade till enkla elementarfall, t.ex. fritt upplagda balkar.

Syftet med föreliggande avhandling är att utveckla flexibla hjälpmedel för dynamiska kontroller av järnvägsbroar. Avhandlingen fokuserar på accelerationer i brons överbyggnad eftersom tidigare studier har visat att det är den som ofta är dimensionerande. Utöver detta görs det också ett flertal fallstudier och probabilistiska analyser.

Ett stort fokus i arbetet har varit att modellen ska vara tillräckligt flexibel för att kunna analysera olika brotyper, samtidigt som mängden indata är begränsad. Följaktligen består modellen av en serie visköst dämpade Bernoulli-Euler balkar som vilar på elastiska upplag. Tåglasten beskrivs med rörliga punktlaster som appliceras direkt på brons överbyggnad utan att interaktion mellan tåg-spår-bro beaktas. Med dessa egenskaper kan modellen användas till att analysera alltifrån fritt upplagda betongbalkbroar till kontinuerliga samverkansbroar. En annan fördel med den föreslagna modellen är att lösningen är exakt eftersom rörelseekvationen har lösts med en Laplacetransform.

Resultaten från fallstudierna visar att betongbroar har lägre dynamisk respons om man jämför med stål- och samverkansbroar. Simuleringarna bekräftar också resultat från tidigare studier som visar att broar med korta spann har svårt att uppfylla accelerationskravet. Detta är något som man också har erfarit i Frankrike, där man efter invigningen av höghastighetslinjen mellan Lyon och Paris uppmätte höga accelerationer hos ett flertal korta broar. Vidare visar också analyserna att en kontinuerlig balkbro har upp till 60 % lägre accelerationer jämfört med om samma bro hade utförts som fritt upplagd.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xii, 47 p.
Series
Trita-BKN. Bulletin, ISSN 1103-4270 ; 116
Keyword
Dynamic, Railway bridge, High-speed train, Moving load, Multi-span beam, Probabilistic
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:kth:diva-122436 (URN)
Presentation
2013-05-31, Projekthallen, Brinellvägen 23, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20130529

Available from: 2013-05-29 Created: 2013-05-21 Last updated: 2013-05-29Bibliographically approved
2. Efficient Modelling Techniques for Vibration Analyses of Railway Bridges
Open this publication in new window or tab >>Efficient Modelling Techniques for Vibration Analyses of Railway Bridges
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The world-wide development of new high-speed rail lines has led to more stringent design requirements for railway bridges, mainly because high-speed trains can cause resonance in the bridge superstructure. Dynamic simulations, often utilising time-consuming finite element analysis (FEA), have become essential for avoiding such problems. Therefore, guidelines and tools to assist structural engineers in the design process are needed.

Considerable effort was spent at the beginning of the project, to develop simplified models based on two-dimensional (2D) Bernoulli-Euler beam theory. First, a closed-form solution for proportionally damped multi-span beam, subjected to moving loads was derived (Paper I). The model was later used to develop design charts (Paper II) and study bridges on existing railway lines (Paper III). The model was then extended to non-proportionally damped beams (Paper IV) in order to include the effects of soil-structure interactions. Finally, the importance of the interaction between the surrounding soil and the bridge was verified by calibrating a finite element (FE) model by means of forced vibration tests of an end-frame bridge (Paper V).

Recommendations on how to use the models in practical applications are discussed throughout the work. These recommendations include the effects of shear deformation, shear lag, train-bridge and soil-structure interactions, for which illustrative examples are provided. The recommendations are based on the assumption that the modes are well separated, so that the response at resonance is governed by a single mode.

The results of the work show that short span bridges, often referred to as `simple´ bridges, are the most problematic with respect to dynamic effects. These systems are typically, non-proportionally damped systems that require detailed analyses to capture the `true´ behaviour. Studying this class of dynamic system showed that they tend to contain non-classical modes that are important for the structure response. For example, the bending mode is found to attain maximum damping when its undamped natural frequency is similar to that of a non-classical mode.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 111 p.
Series
TRITA-BKN. Bulletin, ISSN 1103-4270 ; 145
Keyword
Railway bridge, High-speed train, Closed-form solution, Non-proportional damping, Complex mode
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:kth:diva-201647 (URN)
Public defence
2017-02-24, Kol, Brinellvägen 8, Stockholm, 13:30 (English)
Opponent
Supervisors
Note

QC 20170213

Available from: 2017-02-13 Created: 2017-02-12 Last updated: 2017-02-13Bibliographically approved

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