pcbridges_cantilevermethod

8/8/2019 pcbridges_cantilevermethod

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November 26 29 New Delhi fib Symposium on Segmental construction in concrete 1

Prestressed concrete bridges built

by the cantilever methodDesign and stability during erection

Philippe Vion - Emmanuel Bouchon


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Contents

1. Introduction2. General design

3. Longitudinal post-tensioning4. Temporary cantilevers stability


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Design begins with

knowledge of

successive stagesof construction

1. Introduction


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Cast in place segments


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Pre-cast segments


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! Between 40 and 200 m, even 300 m

! French records: 205 m Rhin bridge (2002)

192 m Sioule viaduct (2005)

190 m Viaur viaduct (1999)

Range of spans


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Bridge over the Rhin river


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Viaduct over the Viaur river


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Viaduct over the Sioule river


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2. General design

LestCintre

With hinges at mid-span (in the old days)

Equal length spans, side spans 0.6L


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Variable length spans

L0,6 L 0,6 ll

( L + l ) / 2l


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Deck depth

h ch p

Parabolic depth variation

Linear depth variation


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Depth ratio

L/(19+(L/7))L/30 to L/35Mid-span hc

7.2 m7 m

L = 120 m

hp

3.3 m3.6 m

L = 120 m

hc

L/(14+(L/45))L/16 to L/18On Pier hp

Static studyCommon case


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One-sided cantilever technique

Bras de la plaine


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Cross section

One cell box

Two cells box


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Box-girder ribbed transversely


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Box-girder with braces


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Twin box-girder


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Boulonnais

Composite girder


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Simply supported

Bearing conditions


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Connected to

the pier

Twin walls


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Twin walls


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On pier segments


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Traveller forms to cast

on pier segment


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Cantilever tendons

2. Post-tensioning


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2

1

3

7 89

5

10 12 14 16

4

111517 13

6 GV

ELEVATION

COUPE TRANSVERSALE

54321

1 2 3 4 5


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Side-span

Internal continuity tendons


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Internal continuity tendons


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ancrage sur pile dviateur en traveAnchor on pier Deflection cross-beam

External continuity tendons


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External tendons: 3 spans

entretoises dviateurs

0,2 0,25 l

Diaphragms Cross-beam


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0,150,35 0,40

Cbles extrieursExternal tendonsDeflection cross-beam


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3. Cantilevers stability

Temporary: Unbalanced cantilever during erection

Accidental: Fall of a traveller form or a precast segment

Poids de l'quipage

2 types of situation

St bilit d i


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Stability devices

Temporary ties


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Top flange anchorage


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Temporary stays +

temporary ties

Vertical tendons

2 cbles

12 T 15 S

2 cbles

27 T 15 S

2 cbles

10 T 15 S

Temporary stays


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