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Linear and non-linear FE-analysis of cracking behavior of wing walls in integral bridges

Ekman, Andreas LU and Sandin, Christoffer (2018) In TVBK-5266 VBKM01 20181
Division of Structural Engingeering
Abstract
Wing walls on slab frame integral bridges has traditionally been designed for mainly earth
pressure and its self-weight. It has also been designed separately from the rest of the bridge.
Traditionally no 3D effects have been considered in the design of the wing walls.
The Swedish Transport Administration (Trafikverket) have recently introduced regulations
stating that 3D effects must be considered when designing wing walls, which means that the
wing wall no longer can be designed separately from the rest of the bridge. This leads to an
introduction of membrane forces in the wing wall which in turn leads to an increase of the
required amount of reinforcement.
This master’s thesis investigates the governing parameters that affect the... (More)
Wing walls on slab frame integral bridges has traditionally been designed for mainly earth
pressure and its self-weight. It has also been designed separately from the rest of the bridge.
Traditionally no 3D effects have been considered in the design of the wing walls.
The Swedish Transport Administration (Trafikverket) have recently introduced regulations
stating that 3D effects must be considered when designing wing walls, which means that the
wing wall no longer can be designed separately from the rest of the bridge. This leads to an
introduction of membrane forces in the wing wall which in turn leads to an increase of the
required amount of reinforcement.
This master’s thesis investigates the governing parameters that affect the magnitude of these
membrane forces and where they arise in the wing wall. A parametric study is conducted
where the goal is to present a relationship between the magnitude of the membrane forces
and the height and length of the wing wall. This part is analyzed using linear FE modeling.
Furthermore, the master’s thesis also investigates how the membrane forces affects the crack
width in the Service Limit State (SLS) of the wing wall. Wing walls that are designed
according to the traditionally procedure are analyzed together with applied membrane forces
acting on the wing wall.
The cracking behavior of the wing wall is checked for long-term loading with an established
non-linear FE modeling considering bond-slip and crack propagation in reinforced concrete.
The model is validated against an experiment of a deep beam and shows sufficient accuracy
regarding crack spacing and conservative crack widths for lower loads.
The results from the linear analysis states that membrane forces cause extra amount of
longitudinal reinforcement in the corner of the wing walls. The parametric study indicates a
tendency for a higher amount of reinforcement needed due to the membrane forces for smaller
wing walls. The parametric study also indicates that for smaller wing walls the membrane
forces are of greater importance since they constitute for a greater part of the total applied
load. For larger wing walls the earth pressure and the self weight gets more dominant and
hence the membrane forces constitute for a lesser part of the total applied load.
The result of the non-linear analysis is in some way contradictory. It indicates that the
membrane forces for short and low wing walls are of lesser problem in SLS, but for short and
high wing walls the membrane forces are of higher importance. The opposite was found in
the linear design. (Less)
Popular Abstract (Swedish)
Linjär och icke-linjär FE-analys av sprickbildning i vingmurar iplattrambroarTrafikverket ställer numera kravsom medfören mer detaljerad dimensioneringsprocessför vingmurar i plattrambroar. Detta innebär en ökad mängd armering i vingmuren, viket gör att kostnaden stiger för konstruktionsdelen. Orsaken till denna ökade mängdarmering har studerats i detta examensarbete.Tekniken för att simulera beteendet hos materialmed hjälp av datorberäkningar utvecklas hela tidenochgörs numeraoftamed Finita Element (FE) -metoden. Noggrannareoch mer omfattande analyser kan då utföraspå kort tid. Det möjliggör även att Trafikverket kan ställa högre krav på dimensioneringen av nya broar. Men det innebär också att nya problem uppstår. Ett sådant problem är... (More)
Linjär och icke-linjär FE-analys av sprickbildning i vingmurar iplattrambroarTrafikverket ställer numera kravsom medfören mer detaljerad dimensioneringsprocessför vingmurar i plattrambroar. Detta innebär en ökad mängd armering i vingmuren, viket gör att kostnaden stiger för konstruktionsdelen. Orsaken till denna ökade mängdarmering har studerats i detta examensarbete.Tekniken för att simulera beteendet hos materialmed hjälp av datorberäkningar utvecklas hela tidenochgörs numeraoftamed Finita Element (FE) -metoden. Noggrannareoch mer omfattande analyser kan då utföraspå kort tid. Det möjliggör även att Trafikverket kan ställa högre krav på dimensioneringen av nya broar. Men det innebär också att nya problem uppstår. Ett sådant problem är att mängden armering ökar förvingmurarna i Sveriges vanligaste brotypi betong, plattrambron. Vingmurarnas uppgift är atthålla emot jordenrunt plattrambron så att en höjdskillnadkvarstår. För att klara det, är de hopgjutnamed resten av brontill en enhet. Men det gör också att vingmurarnapåverkas av de lastersom verkar på resten av bron. Effekterna på vingmurarnafrån dessa laster betraktas som 3D-effekteroch Trafikverket ställer numera krav på att 3D-effekterna måste beaktas. Detta har traditionellt sett inte gjorts, utan vingmuren har dimensionerats separat från resten av bronför jordtryck och egentyngd.Vingmurarna görs iarmerad betong, därarmeringen ska begränsa sprickbreddernaså attkravpå maximal sprickbredd uppfylls.Kravetpå sprickbredder i betongkonstruktioner har skärptsoch tillsammans med kravet på att beakta3D-effekternafåsden ökademängdenarmeringi vingmurarnavid en linjär dimensionering. Men vad händer när betongen börjar spricka? Minskareller till och med försvinnerkrafterna från3D-effekternaochmängdenarmeringi själva verket inte behöver ökas? Detta är en fråga som en icke-linjär analyskan ge svar på. En annan fråga som examensarbetet studerat är om den ökade mängden armering bara gäller för vissa utformningar på vingmuren.Detta har studerats med en parameterstudie, där vingmurarnashöjd och längdvarierats. Till den icke-linjära analysen gjordesen litteraturstudie om sprickbildning i betong och interaktionen mellan armeringen och betongen.Från studien togs sen en FE-modell,sombeaktar sprickbildningenmen också vidhäftningen mellan armeringen och betongen,fram. FE-modellen valideradesmot ett experiment på en hög balk, som också användes för att kalibrera materialvärdentill modellen.Resultatetfrånde linjäraanalysernai examensarbetetvisar på att för mindre vingmurar så ökar den mängd armering som uppkommer av dessa så kallade 3D-effekter i absoluta tal. Det är starkast kopplat till höjden på vingmuren, dvs för lägre vingmurar så bör extra beaktning tas till 3D-effekterna.Examensarbetet visar också på att då vingmuren tillåts spricka upp så är det minst risk för de lågavingmurarna att inte uppfylla sprickkravet. Det påvisas också att förhögavingmurar så ökar risken att inte uppfylla sprickkravet. Detta är delvis motsägelsefulltmot den linjära analysen därdet också påvisas att förjustsmå vingmurar så börextra beaktning tas till 3D-effekter. Det innebär att en entydigslutsatsintegår att dra för de analyserade vingmurarna och att fortsatta studier kring ämnet vore intressant att genomföra. (Less)
Please use this url to cite or link to this publication:
author
Ekman, Andreas LU and Sandin, Christoffer
supervisor
organization
course
VBKM01 20181
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Non linear FE-modelling, Concrete Damage Plasticity, Wing wall, Crack propagation, Serviceability Limit State, Slab Frame Bridge
publication/series
TVBK-5266
report number
TVBK-5266
ISSN
0349-4969
language
English
additional info
Examinator: Oskar Larsson Ivanov
id
8955529
date added to LUP
2018-08-07 10:50:04
date last changed
2018-08-07 10:50:04
@misc{8955529,
  abstract     = {Wing walls on slab frame integral bridges has traditionally been designed for mainly earth
pressure and its self-weight. It has also been designed separately from the rest of the bridge.
Traditionally no 3D effects have been considered in the design of the wing walls.
The Swedish Transport Administration (Trafikverket) have recently introduced regulations
stating that 3D effects must be considered when designing wing walls, which means that the
wing wall no longer can be designed separately from the rest of the bridge. This leads to an
introduction of membrane forces in the wing wall which in turn leads to an increase of the
required amount of reinforcement.
This master’s thesis investigates the governing parameters that affect the magnitude of these
membrane forces and where they arise in the wing wall. A parametric study is conducted
where the goal is to present a relationship between the magnitude of the membrane forces
and the height and length of the wing wall. This part is analyzed using linear FE modeling.
Furthermore, the master’s thesis also investigates how the membrane forces affects the crack
width in the Service Limit State (SLS) of the wing wall. Wing walls that are designed
according to the traditionally procedure are analyzed together with applied membrane forces
acting on the wing wall.
The cracking behavior of the wing wall is checked for long-term loading with an established
non-linear FE modeling considering bond-slip and crack propagation in reinforced concrete.
The model is validated against an experiment of a deep beam and shows sufficient accuracy
regarding crack spacing and conservative crack widths for lower loads.
The results from the linear analysis states that membrane forces cause extra amount of
longitudinal reinforcement in the corner of the wing walls. The parametric study indicates a
tendency for a higher amount of reinforcement needed due to the membrane forces for smaller
wing walls. The parametric study also indicates that for smaller wing walls the membrane
forces are of greater importance since they constitute for a greater part of the total applied
load. For larger wing walls the earth pressure and the self weight gets more dominant and
hence the membrane forces constitute for a lesser part of the total applied load.
The result of the non-linear analysis is in some way contradictory. It indicates that the
membrane forces for short and low wing walls are of lesser problem in SLS, but for short and
high wing walls the membrane forces are of higher importance. The opposite was found in
the linear design.},
  author       = {Ekman, Andreas and Sandin, Christoffer},
  issn         = {0349-4969},
  keyword      = {Non linear FE-modelling,Concrete Damage Plasticity,Wing wall,Crack propagation,Serviceability Limit State,Slab Frame Bridge},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVBK-5266},
  title        = {Linear and non-linear FE-analysis of cracking behavior of wing walls in integral bridges},
  year         = {2018},
}