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PASSERELLE PEDONALI FORMA E STRUTTURA

Prof. Ing. Bruno BriseghellaUniversity of Fuzhou (PRC)

Prof. Ing. Enzo SivieroUniversità IUAV di Venezia

Prof. Ing. Tobia ZordanTongji University (PRC)

Lunedì 23 Maggio 2011Presso lo Spazio Viterbi della Provincia di Bergamo

Bridge types

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What are the type of bridges that we know?

Arch bridges

Girder bridges

Truss bridges

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Cable stayed bridges

Suspension bridges

Stress ribbon bridges

There are also other bridge types but they can be seen as combination of the base types

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Arch +

Stress ribbon

Suspension +

Stress ribbon

Suspension +

Cable stayed

Girder +

Cable stayed

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Terminology

Girder types

Terminology

Girder types

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Terminology

Girder types with integrated substructure and superstructure

Terminology

(Orthotropic) Girder types

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Terminology

Truss types

Terminology

Truss types

Thomas Pratt (1840)

James Warren (1848)

William Howe (1840)

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Terminology

Truss types

August von Pauli (1865)Poli truss

Albert Fink (1860)

Terminology

Truss types

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Terminology

Arch types

Terminology

(Tied) Arch types

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Terminology

(Trussed) Arch types

Terminology

(Trussed) Arch types

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Terminology

Cable stayed types

Force distribution in the girder (- compression; + tension)

Self-anchored deck Externally restrained deck

Terminology

Cable stayed types

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Terminology

Tower types

Single

Double

Portal

Inverted Y

A shaped

Terminology

Suspension type

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TraditionalAccording to their developement in history they can be numbered as followsA. MasonryB. Natural stoneC. TimberD. Cast ironE. ConcreteF. Prestressed concreteG. Steel

New materialsThis materials are still almost at an experimental stageG. AluminiumH. Stainless steelI. Prestressed stoneL. GlassM. Composites

Construction materials

TipologieSpansMax theoretical

Suspension

Cable stayed

Cantilever truss

Arch

Continuous truss

Continuous truss

Simple span truss

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Cos

t/m2

L (span)

Girder Arch

Suspension

Cab. stayed

Erection cost

Static scheme Material Economic span

Concrete

Steel

Steel

Concrete

Concrete

Steel

Steel

Steel

Steel

Girder

Truss

Spandrel arch

Trussed arch

Cable stayed

Suspension

Dea

d lo

ads

(t/m

2 )

L (m)

For girder types, structural dead loads grows more thanlinerarly with the increase in span.

Dead loads

M = K P L2

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In case of a bridge of 100m span, dead loads can absorb up to90% of the bearing capacity of construction materials. The remaining 10% is devoted to the bearing of live loads.

One of the main goal during design process must be the limitation of self load.

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Structural optimization process can get through the following phases:

A. Placement of the construction material of the main structure so to obtain a efficient scheme associated to the minimization of total loads. Whenpossible, use open T or H sections or use a close box section.

B. Use of construction materials with a convenient strength/weight ratio. When using concrete evaluate the possibility of adopting lightweightaggregates or high strength concrete. In order to maximize the exploitationof mechanical characteristics of construction materials, the use of composite section should be an option.

σadm/γ − concrete Rck = 40 MPa σall/γ = 490 m

- steel S355 σall/γ = 3077 m

C. Change bridge type. The use of an arch or a suspension deck can help in limiting the stress distribution and consequently the dead loads.

Main features of common bridge types

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Simply supportedStatic schemePrefabricated concreteConstruction material

< 30 – 40 mSpan

Girder bridge

Simple span / continuousStatic scheme

Composite steel and concrete Contsruction material

30– 50mSpan

Girder bridge

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ContinuousStatic schemePrestressed concreteConstruction material

> 40 - 50 m (box girder)Span

Girder bridge

ContinuousStatic scheme

Composite steel and concreteConstruction material

40 - 100 m (box girder)Span

Girder bridge

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ContinuousStatic scheme

Steel Construction material

100 – 200m (orthotropic box girder)Span

Girder bridge

L < 50 m. Short and medium span

A. Pretressed Concrete Bridges. B. Composite steel-concrete bridges

Girder bridge

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L > 50 m. Large span

A. Pretressed Concrete Bridges. B. Composite steel-concrete bridges/orthotropic box girder

Girder bridge

Girder bridge

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Simply supportedGirder Bridges

Gerber GirderBridge

Simply supportedGirder Bridgeswith continuousslab

ContinuousGirder Bridges

Span Advantages Disadvantage

- 40÷50 m p.c. or Steel-concrete

- 60÷80 m steel

- < 200 m steel

- < 100 m Steel-concrete

- < 200 m p.c.

-Erection more easy

-Use of prefabrication

- Less sensible tofoundations settlement

- Isostatic structure

-Less material than simplysuported

-i

- Less Joints than simplysupported (every 150÷250 m and not every 30÷40 m asfor simply supported)

-Erection more easy and fast

- Better rigidity

- Less material

- Better durability

- Less rigidity

- less confort

- Durability problems(bearings and joints)

-More materials

- Difficulty of the replacement of the bearings (Gerber saddle)

- Durability of the continuous slab

- sensible to foundationssettlement

- Use of prefabrication ismore difficult

A. Deck Concrete (m3/m2)

Prest. steel rebar (kg/m2)

Steel rebar (kg/m2)

A1. Precast prestressed beams L = 20 m 0,40 ÷ 0,45 8 ÷ 10 30 ÷ 35 A2. Precast prestressed beams L = 30 m 0,45 ÷ 0,50 12 ÷ 14 35 ÷ 40 A3. Precast prestressed beams L = 40 m 0,50 ÷ 0,55 17 ÷ 19 40 ÷ 45 A4. Precast prestressed beams L = 20 m 0,55 ÷ 0,60 12 ÷ 15 25 ÷ 35 A5. Concrete slab girder L = 30 m 0,50 ÷ 0,60 12 ÷ 14 40 ÷ 50 A6. Prestressed concrete box girder L = 60 m 0,60 ÷ 0,80 24 ÷ 26 45 ÷ 55 A7. Prestressed concrete box girder L = 90 m 0,80 ÷ 1,00 35 ÷ 40 55 ÷ 65 A8. Composite steel-concrete L = 40 m 0,25 ÷ 0,30 / 200 ÷ 2501 A9. Composite steel-concrete L = 60 m 0,25 ÷ 0,30 / 250 ÷ 3001 1 Steel plates B. Pier Span length

m Concrete

m3/m of pier Steel rebar Kg/m of pier

B1. Circular pier H = 15 m 20 ÷ 30 3 ÷ 3,5 200 ÷ 300 B2. Box pier H = 20 m 30 3 ÷ 3,5 250 ÷ 350 40 3 ÷ 4 300 ÷ 400 B3. Box pier H = 40 m 40 4 ÷ 5 350 ÷ 500 50 5 ÷ 7 400 ÷ 600 B4. Box pier H = 60 m 60 7 ÷ 10 550 ÷ 700

Girder bridge1. Concrete bridges

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2. Steel bridges

Girder bridge

Footbridges (B = 2 ÷ 4 m)

Road Bridges (B = 10 ÷ 20 m)

Railway Bridges (single-track)

Lm (m) g (kg/m) steel

Lm (m) g (kg/m2) steel

Lm (m) g (kg/m) steel

10 - 20 100 ÷ 120 10 1200 20 100 ÷ 130 40 140 ÷ 180 20 1700 30 150 ÷ 200 60 200 ÷ 250 30 2200 40 210 ÷ 280 80 250 ÷ 300 40 2700 50 300 ÷ 380 100 300 ÷ 350 50 3200 60 370 ÷ 440 120 350 ÷ 400 60 3700 70 450 ÷ 550 150 400 ÷ 450 70 4200 80 - 200 450 ÷ 500 80 4800 90 - 250 500 ÷ 550 90 5500

100 - 300 550 ÷ 600 100 6400

Frame bridge

Static systems of frame integral bridges

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Vertical Piers Inclined PiersGirder ⇒ Bending + AxialGirder ⇒ Bending

Frame bridge

Tied archStatic scheme

Concrete / Steel / CompositeConstruction material

100 - 300 mSpan

Arch bridge

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Two hinges through archStatic scheme

Concrete / Steel / CompositeConstruction material

100 - 500 mSpan

Arch bridge

VariousStatic scheme

Concrete / Steel / CompositeConstruction material

200 - 1000 mSpan

Cable-stayed bridge

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VariousStatic scheme

Steel / CompositeConstruction material

≥ 500 mSpan

Suspension bridge

Simple beamStatic scheme

Steel / CompositeConstruction material

30 - 80 mSpan

Railway girder bridge

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Simple beamStatic scheme

Steel / CompositeConstruction material

30 – 50 mSpan

Railway pony truss bridge

Simple beamStatic scheme

SteelConstruction material

50 - 150 mSpan

Railway through truss bridge

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• Design speed determines bend radius, transversal and longitudinal gradients. • Typical values are:

.deck width = 6÷30 m (typical ∼ 12 m)

.longitudinal gradient < 7% (10÷12% special cases)

.transversal gradient ≥ 5 ÷ 7%

.vertical radius > 1000 ÷ 23.000 m

.horizontal radius = 40 ÷ 5000 m for design speed = 50 ÷ 140 km/h• Maximum vertical deflection under live loads: 1/500• Design loads roughly 7 ÷ 8 kN /m² ( 700 ÷ 800 kg/m²), (∼3 t/m most loaded lane, ∼1.5

t/m others).

Road bridges: traffic loads

• Maximum vertical deflection under live loads: f/l < 1/1000.

• Replacability of girders with no traffic interruption leads to a preference for simplebeams.

• Longitudinal gradient ~ 0,2 %

• Design loads: ~ 10 t/m per track.

Railway bridges: traffic loads and features

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Longest bridge in the world

World records in span

Girder bridges

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Steel truss girder bridges

Prestressed concrete girder bridges

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Quebec Bridge (L=549m) Quebec city, Canada 1917

Fifth of fourth (L=521m) Edimburgh, UK 1890

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Minato bridge (L=521m) Osaka, Japan1974

Shibanpo Bridge (L=330m) Chongqing, China 2006

The Shibanpo bridge is a multi-span in-situ concrete box girder bridge with an overalllength of 1104m and a main span of 330m, it also boasts the longest box girder span in the world. The central 108m of the main span was designed as a steel box girder to saveweight, and was delivered to site in 3 segments - a 1325 tonne, 103m centre section and two smaller 100 tonne 2.5m long steel transition pieces that connect it to the concrete deck at either end.

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Stolmasundet Bridge (L=301m) Austevoll, Norway1998

Platano bridge in Salerno, Italy

L=291m, 1978, S. Zorzi

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LONGEST STEEL BOX GIRDER BRIDGES

0

50

100

150

200

250

300

350

1950 1960 1970 1980 1990 2000 2010

YEAR OF COMPLETION

SPA

N L

ENG

TH (m

)

CONCRETE GIRDER BRIDGES

0

50

100

150

200

250

300

350

1940 1950 1960 1970 1980 1990 2000 2010

YEAR OF COMPLETION

SPA

N L

ENG

TH (m

)

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Milestone Segmental Bridges

0

50

100

150

200

250

300

350

1940 1950 1960 1970 1980 1990 2000 2010

YEAR

SPA

N L

ENG

TH (m

)

Balduinstein

Stolmasundet

KororBendorf

Worms

Shibanpo

Arch bridges

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Steel arch bridges

Concrete arch bridges

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Rank Name Span(m) Year Nation

1 Chaotianmen Bridge 552 2009 China

2 Lupu Bridge 550 2003 China

3 New River Gorge Bridge 518 1977 USA

4 Bayonne Bridge 504 1931 USA

5 Sydney Harbour Bridge 503 1932 Australia

6 Wushan Bridge 460 2005 China

7 Wanxian Yangtze River Bridge 420 1997 China

8 Caiyuanba Bridge 420 2007 China

9 Daning River Bridge 400 2010 China

10 Lianxiang Bridge 400 2007 China

Caotienmen, Chongqing (L=552m)2008

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Lupu bridge, Shanghai (L=550m) Lin Yuan Pui2004

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New River Gorge, USA (L= 518.3m)Michael Bakers 1978

The Hellgate Bridge in New York (L = 298m) by Gustav Lindenthal1916

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Sydney Harbour Bridge (L = 503m) by Ralph Freemann1924 - 1932

Bayonne Bridge in NY (L = 503.6m) Othmar Ammann1928 - 1931

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Krk Bridge, Krk iland, Croatia (L = 390 and 224m)1980

Wanxian Bridge (L = 420m)Wanzhou, China1997

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Competition of Arch Span Length

0

100

200

300

400

500

600

1850 1900 1950 2000 2050

Year

Spa

n Le

ngth

s (m

)

Hel

lgat

e

Sydn

ey H

arbo

rBa

yonn

e

New

Riv

er G

orge Lu

puC

aotie

nmen

Pia

Mar

iaG

arab

it

St. L

ouis

Luis

I

Man-Chung Tang: “Concept of Structures”

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ARCH BRIDGES

0

100

200

300

400

500

600

1920 1940 1960 1980 2000 2020YEAR

SPA

N L

ENG

TH (m

)

CONCRETE

STEEL

Man-Chung Tang: “Concept of Structures”

ARCH BRIDGES

0

100

200

300

400

500

600

1920 1940 1960 1980 2000 2020YEAR

SPA

N L

ENG

TH (m

)

CONCRETE

STEEL

Man-Chung Tang: “Concept of Structures”

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Suspension bridges

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Rank Name Span(m) Year Nation

1 Akashi Kaikyo Bridge 1991 1998 Japan

2 Xihoumen Bridge 1650 2008 China

3 Great Belt Bridge 1624 1997 Denmark

4 Runyang Yangtze River Bridge 1490 2005 China

5 Humber Bridge 1410 1981 England

6 Jiangyin Yangtze River Bridge 1385 1999 China

7 Tsing Ma Bridge 1377 1998 China

8 Verrazano-Narrows Bridge 1298 1964 USA

9 Golden Gate Bridge 1280 1937 USA

10 Yangluo Yangtze River Bridge 1280 2007 China

Akashi Kaikyo Bridge (L = 1991m)Kobe, Japan1998

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Xishoumen Bridge (L = 1650m)Zhoushan Island, China2008

Humber Bridge (L = 1410m)Kingstone-upon-Hull, UK1981

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Verranzano Narrows Bridge (L = 1298m)New York NY, USA1964

Golden Gate Bridge (L = 1280m)San Francisco, USA1937

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50

Longest Suspension Bridge Spans

0

500

1000

1500

2000

2500

1800 1850 1900 1950 2000 2050

Year

Span

Len

gth

(m)

Men

ai Broo

klyn G

. Was

hing

ton

Gol

den

Gat

e

Verr

anza

no

Hum

ber

Stor

ebel

t Akas

hi

Sarin

eVa

lley

Iron Steel

Cable-stayed bridges

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Rank Name Span(m) Year Nation

1 Sutong Bridge 1088 2008 China

2 Stonecutters Bridge 1018 2009 China

3 Edong Bridge 926 2010 China

4 Tatara Bridge 890 1999 Japan

5 Pont de Normandie Bridge 856 1995 France

6 Jingyue Yangtze River Bridge 816 2010 China

7 Incheon Bridge 800 2009 Korea

8 Shanghai Yangtze River Bridge 730 2009 China

9 Minpu Bridge 708 2010 China

10 Third Nanjing Bridge 648 2005 China

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Sutong Bridge (L = 1088m)Suzhou-Nantong, China2008

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Stonecutters Bridge (L = 1018m)Hong Kong, China2008

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Tatara Bridge (L = 890 m)Onomichi - Imabari , Japa1999

Normandie Bridge (L = 856m)Le Havre, France1995

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Longest Cable-Stayed Bridge Spans

0

200

400

600

800

1000

1200

1950 1960 1970 1980 1990 2000 2010 2020

Year

Span

Len

gths

(m)

Stro

msu

ndTh

. Heu

ss

Leve

rkus

en

Knie

Neu

enka

mp

Sain

Naz

aire

Anna

cis

Yang

puN

orm

andy

Tata

ra

Suto

ng