Dynamic Analysis of Portal Frame Railway Bridges - Case Studies Investigating the Structural Response
(2020) In TVBK-5281 VBKM01 20201Division of Structural Engineering
Department of Building and Environmental Technology
- Abstract
- As the world continues to see an increase in carbon dioxide emissions, actions aiming towards reducing man's negative impact on the environment are paramount. To be able to compete with the air travel industry, the Swedish Transport Administration suggests a vast expansion of the existing railway system. This includes the construction of high speed railroads connecting the largest urban areas of Sweden. With such a development comes numerous railway bridges, whom will have trains operating at speeds exceeding 200 km/h and thus demanding a dynamic evaluation. An immense amount of aspects require consideration when conducting such analyses. However, simple and effective methods are crucial in order to facilitate the design process for the... (More)
- As the world continues to see an increase in carbon dioxide emissions, actions aiming towards reducing man's negative impact on the environment are paramount. To be able to compete with the air travel industry, the Swedish Transport Administration suggests a vast expansion of the existing railway system. This includes the construction of high speed railroads connecting the largest urban areas of Sweden. With such a development comes numerous railway bridges, whom will have trains operating at speeds exceeding 200 km/h and thus demanding a dynamic evaluation. An immense amount of aspects require consideration when conducting such analyses. However, simple and effective methods are crucial in order to facilitate the design process for the engineer.
In this thesis, three statically designed portal frame bridges of span lengths ranging from 6.5--18 m were analysed with regards to their dynamic behaviour. The commercial Finite Element Analysis software BRIGADE/Plus was used to evaluate their response. In attempting to map out the structural behaviour of the assessed railway bridges, while at the same time elevating the authors' general knowledge within the field of railway bridge dynamics, investigations were conducted to verify the viability of the methods suggested in Eurocode. Furthermore, previous research indicates that the use of a higher soil stiffness makes for a better representation of reality when conducting dynamic analyses. Therefore, parametric studies were performed in order to verify said proclamation with regards to two calculation methods.
Based on acquired results, the study concludes that the estimative procedure, proposed in Eurocode, meant to determine the dynamic responses through magnification of each of the statically retrieved reactions is somewhat flawed. In utilisation of specific modeling concepts, certain configurations generate highly disproportionate magnifiers, and thus, non-viable approximations. Generally, this behaviour is amplified with decreasing span length and declining soil stiffness. Indications are that shorter bridges are more susceptible to influence from a certain eigenmode, which causes the established behaviour. When approaching the dimensions of the largest bridge investigated, this becomes a non-issue; the same goes for the introduction of soil parameters which are vastly stiffer than those proposed by Trafikverket. Furthermore, with the introduction of larger soil stiffness parameters, a tendency to lessen the vertical acceleration response is found. Again, however, this alteration has a diminishing influence on portal frame bridges with larger dimensions. (Less) - Popular Abstract (Swedish)
- Eftersom världen fortsätter att se en ökning av koldioxidutsläpp, är åtgärder för att minska människans negativa miljöpåverkan av största vikt. För att kunna konkurrera med flygindustrin föreslår Trafikverket en omfattande utökning av det existerande järnvägsnätverket. Detta inkluderar byggnation av höghastighetsjärnvägar, som skall koppla samman Sveriges storstäder. Sådana planer innefattar även järnvägsbroar, där tåg med operativa hastigheter över 200 km/h kommer att passera, vilket innebär att broarna behöver undergå dynamisk analys. En sådan utvärdering medför en mängd aspekter att ta hänsyn till och behovet av simpla samt effektiva metoder är avgörande för att facilitera dimensioneringsprocessen för ingenjören.
I detta examsarbete... (More) - Eftersom världen fortsätter att se en ökning av koldioxidutsläpp, är åtgärder för att minska människans negativa miljöpåverkan av största vikt. För att kunna konkurrera med flygindustrin föreslår Trafikverket en omfattande utökning av det existerande järnvägsnätverket. Detta inkluderar byggnation av höghastighetsjärnvägar, som skall koppla samman Sveriges storstäder. Sådana planer innefattar även järnvägsbroar, där tåg med operativa hastigheter över 200 km/h kommer att passera, vilket innebär att broarna behöver undergå dynamisk analys. En sådan utvärdering medför en mängd aspekter att ta hänsyn till och behovet av simpla samt effektiva metoder är avgörande för att facilitera dimensioneringsprocessen för ingenjören.
I detta examsarbete presenteras dynamiska analyser av tre statiskt dimensionerade plattrambroar med spannlängder mellan 6.5--18 m. Utredningen genomfördes med hjälp av den kommersiella programvaran BRIGADE/Plus, vilken använder sig av Finita Elementmetoden som beräkningsverktyg. I ett försök att kartlägga det strukturella beteendet hos de tre järnvägsbroarna, och samtidigt öka författarnas kunskap inom området, genomfördes undersökningar för att verifiera gångbarheten i metoderna föreslagna i Eurocode. Tidigare forskningsresultat ger tydliga indikationer på att en högre markstyvhet bör användas vid utförande av dynamiska analyser, än vid motsvarande statiska. Sålunda utfördes parameterstudier där två beräkningsmetoder togs i bruk.
Baserat på resultaten dras slutsatsen att det approximativa förfarandet i Eurokoden, utformat för att bestämma strukturens dynamiska respons genom förstoring av de statiskt bestämda storheterna, är något bristfällig. Användning av specifika modelleringskoncept genererar för somliga konfigurationer oproportionerliga förstoringsfaktorer och därmed mindre tillförlitliga uppskattningar. I allmänhet kan man utröna att detta beteende förstärktes vid kortare broar och lägre markstyvhet. Studien visar på att kortare broar är mer mottagliga till inverkan från ett visst egenmod, som påvisats vara orsaken till sådana resultat. Vid ökad spannlängd, såsom för den tredje bron, är detta ett icke-problem. Detsamma kan sägas om markstyvheten, efter en väsentlig ökning jämfört med Trafikverkets rekommenderade värden. En sådan höjning genererade också lägre vertikala accelerationer i broplattan. Emellertid var även detta ett beteende som verkar avta med ökade dimensioner. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9021906
- author
- Berg, Benjamin LU and Nyberg, Pontus LU
- supervisor
- organization
- alternative title
- Dynamiska Beräkningar av Järnvägsbroar
- course
- VBKM01 20201
- year
- 2020
- type
- H3 - Professional qualifications (4 Years - )
- subject
- keywords
- Dynamic Analysis, Portal Frame Bridges, High Speed Trains, Railway Bridges, Finite Element, Resonance, Modal Analysis, BRIGADE/Plus
- publication/series
- TVBK-5281
- report number
- TVBK-5281
- ISSN
- 0349-4969
- language
- English
- additional info
- Examinator: Ivar Björnsson
- id
- 9021906
- date added to LUP
- 2020-06-24 08:29:07
- date last changed
- 2020-06-24 08:29:07
@misc{9021906,
abstract = {{As the world continues to see an increase in carbon dioxide emissions, actions aiming towards reducing man's negative impact on the environment are paramount. To be able to compete with the air travel industry, the Swedish Transport Administration suggests a vast expansion of the existing railway system. This includes the construction of high speed railroads connecting the largest urban areas of Sweden. With such a development comes numerous railway bridges, whom will have trains operating at speeds exceeding 200 km/h and thus demanding a dynamic evaluation. An immense amount of aspects require consideration when conducting such analyses. However, simple and effective methods are crucial in order to facilitate the design process for the engineer.
In this thesis, three statically designed portal frame bridges of span lengths ranging from 6.5--18 m were analysed with regards to their dynamic behaviour. The commercial Finite Element Analysis software BRIGADE/Plus was used to evaluate their response. In attempting to map out the structural behaviour of the assessed railway bridges, while at the same time elevating the authors' general knowledge within the field of railway bridge dynamics, investigations were conducted to verify the viability of the methods suggested in Eurocode. Furthermore, previous research indicates that the use of a higher soil stiffness makes for a better representation of reality when conducting dynamic analyses. Therefore, parametric studies were performed in order to verify said proclamation with regards to two calculation methods.
Based on acquired results, the study concludes that the estimative procedure, proposed in Eurocode, meant to determine the dynamic responses through magnification of each of the statically retrieved reactions is somewhat flawed. In utilisation of specific modeling concepts, certain configurations generate highly disproportionate magnifiers, and thus, non-viable approximations. Generally, this behaviour is amplified with decreasing span length and declining soil stiffness. Indications are that shorter bridges are more susceptible to influence from a certain eigenmode, which causes the established behaviour. When approaching the dimensions of the largest bridge investigated, this becomes a non-issue; the same goes for the introduction of soil parameters which are vastly stiffer than those proposed by Trafikverket. Furthermore, with the introduction of larger soil stiffness parameters, a tendency to lessen the vertical acceleration response is found. Again, however, this alteration has a diminishing influence on portal frame bridges with larger dimensions.}},
author = {{Berg, Benjamin and Nyberg, Pontus}},
issn = {{0349-4969}},
language = {{eng}},
note = {{Student Paper}},
series = {{TVBK-5281}},
title = {{Dynamic Analysis of Portal Frame Railway Bridges - Case Studies Investigating the Structural Response}},
year = {{2020}},
}