bde long span bridges supplement

7/26/2019 BDE Long Span Bridges Supplement

1/60

LONG-SPANBRIDGES

THE DEFINITIVE PUBLICATION FOR BRIDGE PROFESSIONALS WORLDWIDE | WWW.BRIDGEWEB.COM

SECTOR FOCUS


2/60

Naeem Hussain Richard Hornby Steve Kite

[email protected] [email protected] [email protected]

Global UK, Middle East & Africa East Asia

Peter Burnton Marcos Sanchez Matt Carter [email protected] [email protected] [email protected]

Australasia Europe Americas

Forth Replacement Crossing, Scotland

Whether to span nations, make a statement or

improve everyday links, Arup crafts better bridgesArup works in active partnership with clients to understand their needs so

that the solutions make their bridge aspirations possiblebig and small.The Arup global specialist technical skills blended with essential local

knowledge adds unexpected benefts.

www.arup.com


3/60

Long-span bridges have always held a fascination for structural engineers and

indeed, for the general public with the longest bridges of each type generally

categorised by their worldwide rating. When a new record is set, as seems to happen

on a regular basis, the latest title-holder is accorded great publicity and guaranteed

an audience around the world.

But as our supplement makes clear, the biggest challenges in long-span bridge engineering

are not necessarily the record-breaking structures. These may be challenging when they

are under construction particularly if they are being built in regions which experience

extreme weather conditions but often they employ tried and tested design approaches and

construction technologies, with the longer spans generally driven by topography or other

project-specific criteria.

The skills of engineers and architects working on any long-span bridges can often be testedmore thoroughly when it comes to designing them for highly-seismic locations, using unusual

combinations such as those with multiple cable-supported spans in series, or being tasked with

creating aesthetically-pleasing structures at this kind of scale.

In this special supplement we kick off with an overview of long-span bridges in China, where

many of the worlds longest spans can currently be found; canvass opinion on the hot-topics in

long-span bridges around the world, and report on some of the ongoing, planned and recently-

completed long-span crossings. It is by no means exhaustive, that would be impossible in a

publication of this size, but I hope it will give readers a flavour of some of the challenges the

industry is facing today

Editor Helena Russell

T+44 20 7973 4697 F +44 20 7233 [email protected]

Deputy editorJos Mara Snchez de MuniinT+44 1935 37 [email protected]

Advertisement sales managerLisa BentleyT+44 20 7973 4698 F+44 20 7233 [email protected]

For subscriptions queries please contactT+44 20 7973 6694 F+44 20 7233 [email protected]

Bridge design & engineering

32 Vauxhall Bridge RoadLondon SW1V 2SS, UKT+44 20 7973 6400

ISDN +44 20 7931 0833Wwww.bridgeweb.com

International advertisement salesGermany, Austria, Switzerland & Scandinavia Jrg HellerT+44 20 7973 4698 F+44 20 7233 5053Ej [email protected]

Italy, Spain, Portugal & Eastern Europe Fulvio BonfigliettiT/F+39 0171 95 59 [email protected]

North America David FidlerT+1 905 829 9340 F+1 905 829 [email protected]

Circulation manager Maggie SpillaneDesigner Lisa ArcangeliProduction Gareth ToogoodManaging director Graham Bond

ContributorsLisa Russell, Man-Chung Tang

Bridge design & engineeringis published quarterly and is available onsubscription at the rate of UK105/162/US$218 per year, which includesfour issues of Bd&eand eight issues of Bridge updatenewsletter.Subscription payment can only be accepted in the currency of thecountry in which a company is registered. If not registered in the UK, theEU or the US, payment should be made in US dollars.

Bridge design & engineering(ISSN No: 1359-7493, USPS No: 003-140) ispublished quarterly by Hemming Group and distributed in the USA byby SPP, 17B S Middlesex Ave, Monroe NJ 08831. Periodicals postage paidat New Brunswick, NJ. POSTMASTER: send address changes to Bridgedesign & engineering, 17B S Middlesex Ave, Monroe NJ 08831.

Every effort is made to ensure that the content of this publication

is accurate but the publisher accepts no responsibility for effects arisingthere from. We do not accept responsibility for loss or damage tounsolicited contributions. Opinions expressed by the contributors andadvertisers are not necessarily those of the publisher. This publicationis protected by copyright and no part may be reproduced in whole or inpart without the written permission of the publisher.

Printed by Latimer TrendISSN 1359-7493Published by Hemming Information Services(a division of Hemming Group Limited)Hemming Group Ltd 2016

Helena RussellEditor

Contents

Editors comment

04 THE LONG GAME: Half of the worlds top twenty longest-span suspensionbridges are in China, as are six out of nine of the longest spans of other types of

bridges. Man-Chung Tang reports on recent progress in the current internationa

hot-spot for long-span bridges

14 EXTREME LENGTHS: Some of our longest-span bridges have been aroundfor several decades now, and to a large extent the technologies and engineering

know-how of these structures are tried and tested. Lisa Russell explores the

influences on long-span bridge design today, and the challenges of our ageing

structures.

34 SUBSCRIBE: Get your own copy of Bridge design & engineeringevery quarter.

43 SPONSORED COMPANY PROFILES: Our commercial partners highlighttheir expertise and recent projects in the asset management sector.

43 INDEX OF FEATURED COMPANIES

LONG-SPAN BRIDGES

LONG-SPAN BRIDGES SUPPLEMENT 2016 www.bridgeweb.com 0

Cover image: Rendering of Hlogaland Bridge which isunder construction in Norway(Dissing & Weitling)

Bridge design & engineering group

@bdebridgeweb


4/60

04 www.bridgeweb.com LONG-SPAN BRIDGES SUPPLEMENT 2016

LONG-SPAN BRIDGES

The long game

Half of the worlds top twenty longest-spansuspension bridges are in China, as are six out

of nine of the longest spans of other types ofbridges. Man-Chung Tangreports on recentprogress in a hot-spot for long-span bridges


5/60

LONG-SPAN BRIDGES SUPPLEMENT 2016 www.bridgeweb.com

LONG-SPAN BRIDGES

Over the last 30 years, China

has built a huge network of

highways of about 4,000,000km

of regular highways and more

than 75,000km of expressways. A

comparison of Chinas expressway system

to the US Interstate bears discussion. The

US began to build the Interstate system in

1956 while China did not start until 1987.Being the strongest economy in the world

at that time, the US interstate system took

off very quickly. By contrast, China was a

very poor country in 1987 and the countrys

network of expressways was slower to

develop. But eventually, it overtook the

US and now has the greatest length of

expressways of any country in the world.

The expansion of Chinas highway system

is not the only reason so many bridges are

needed; its cities are also developing and

need increased river-crossing capacity. It

is somewhat sobering to consider that in

1985, there were only three bridges over

the entire 6,300km length of the Yangtze

River one in Chongqing, one in Nanjing

and one in Wuhan.

Today, there are more than a hundred.

In addition to those major bridges, a large

number of crossings have also been built

over other rivers and valleys, and many of

these are long span bridges.

How is long-span defined? Among the

Bridge type Name Span (m) Country Yearcompleted

Suspension Akashi-Kaikyo 1991 Japan 1998

Xihoumen 1650 China 2009

Great Belt East 1624 Denmark 1998

Cable-stayed Russky 1104 Russia 2012

Sutong 1088 China 2008

Stonecutters 1018 China 2009

Arch Chaotianmen 552 China 2009

Lupu 550 China 2003

Bosideng 530 China 2012

Girder Shibanpo 330 China 2006

Stolmasundet 301 Norway 1998

Costa e Silva 300 Brazil 1974

four categories of bridges in the world

girder bridges, cable-stayed bridges, arch

bridges and suspension bridges the

definition of long span depends on the

type of structure. A 300m span might be

very long in a girder bridge, but it would

be considered very short if it were a

suspension bridge.

The table below lists the three longestspans in the world in the four categories

of bridges; of these 12, seven of them are

in China, and of the 20 longest suspension

bridges, which are also the 20 longest

spans of all bridges either completed or

under construction, ten of them are in

China. There is no doubt this bridge boom is

an exciting time for bridge lovers.

In terms of bridge technology, China is a

latecomer, but it has been a rapid learner.

The countrys first real long-span bridge,

the 423m-span cable-stayed Nanpu Bridge

in Shanghai, was opened to traffic in 1992,

while most of the longest spans in Europe

and North America were completed many

years previously. Real long-span suspension

bridges flourished in the 1930s in the USA

while segmental girder bridges and cable-

stayed bridges began in the early 1950s

in Germany. So bridge building is neither

a modern technology nor considered a

high-tech venture. Building a conventional

long-span bridge today even the worlds

longest span is only contingent on cost,

as the technology for building bridges

is already mature. In many ways it is the

speciality bridge that hold more interest,

though they may not be the longest spans

in the world, or even in China.

Girder bridges

Of all bridge types, the girder bridge is the

most common. But the Shibanpo Bridge in

Chongqing, which is a 330m-span hybrid

structure, currently holds the world record

for span length. It is located next to an

existing girder bridge which was completedin 1981 and because of the proximity of

the two bridges, it was natural to design

the new structure as a girder bridge for

aesthetic reasons.

The span arrangement of the old


6/60


LONG-SPAN BRIDGES

bridge has two main spans of 156m and

174m, and the original intention was to align

the piers of the new bridge with those of

the old bridge. However the Waterways

Authority was concerned that the 174m-long

main span of the old bridge was already

very tight for modern river traffic and

the presence of the new piers would have

created a tunnel effect for ship navigation.

Thus, the authority insisted that the pier

between the two spans be deleted, creating

a 330m-long main span. To date, the longest

all-concrete box girder bridge is the 301m

span Stolmasunde Bridge in Norway, which

was completed in 1998, while the longest

all-steel girder bridge is the 300m span

Costa e Silva Bridge in Brazil, completed in

1974.

For the Shibanpo Bridge, with its

330m-long main span, a concrete structure

would have been too heavy and the long-

term deflection would have been difficult

to control, especially at the middle portion

of the bridge. A steel bridge on the other

hand would have required very thick plates

and would have been too difficult and too

expensive to fabricate, especially the girder

portion over the piers.

To avoid these problems, TY Lin

International designed a prestressed

concrete girder bridge with a 130m-long

steel box at the mid span. The concrete

portion of the bridge was built segmentally

using form travellers a large number of

concrete segmental bridges had already

been built in China, so this was rather

routine.

The steel box girder was fabricated

in Wuhan, which is about 1,000km

downstream of the bridge site. To facilitate

its transportation, the steel box was

designed to act as a barge as well. After

closing the two ends it was launched like a

ship onto the Yangtze River and towed to

the site where it was lifted and connected

to the two cantilevers. The lifting operation

was completed within the permitted 12-hour

window and the bridge was opened to

traffic in 2006.

Arch spans

The worlds three longest span arch

bridges are all in China; the 552m span

Chaotianmen Bridge which crosses the

Yangtze River in Chongqing; the 550m span

Lupu Bridge crossing the Huangpu River


7/60

With a 116-year

history of completing

the worlds most

challenging projectsbehind us, were fully

focused on the future.

Because it will always

be legendary.

LEGENDARY

CONSTRUCTION

The Queensferry Crossing, Edinburgh, Scotla

Photo Credit: Transport Scotla

career opportunities: americanbridge.ne


8/60


LONG-SPAN BRIDGES

in Shanghai and the 530m-span Bosideng

Bridge over the Yangtze River in Luzhou.

The Chaotianmen Bridge is a truss arch,

the arch ribs of the Lupu Bridge have box

shape cross-sections and the arch ribs of

the Bosideng Bridge are concrete-filled

steel tubes. The design and construction

of first two bridges was fairly conventional

with the Chaotianmen Bridge constructedas a pair of cantilevers and the arch ribs of

the Lupu Bridge built using highlines and

temporary cable stays.

China has built more than 400 arch

bridges using concrete filled steel tubes, as

this type of construction is very economical

in China and many steel fabricators have

acquired the equipment needed to produce

the spirally-welded steel tubes used for

this type of arch bridge. Erection is mainly

done using highlines and most of these arch

spans are relatively moderate in length.

But the Bosideng Bridge in Luzhou,

Sichun, which opened to traffic last year,

has a span of 530m, with the steel portion

of the arch measuring 518m. The arches

typically consist of a group of steel tubes

braced against each other by smaller

steel tubes. The main tubes are filled

with concrete after the arch has been

constructed. To ensure that the tubes were

completely filled with concrete, the vacuum

pumping method was successfully applied

to the Bosideng Bridge for the first time.

Currently, the worlds longest concrete

arch span is the Wanxian Bridge in

Chongqing a 420m span bridge which

crosses the Yangtze River in Wanxian and

was opened to traffic in 1997. The arch rib

is shaped like a catenary and is 16m wide

and 7m deep with a rectangular triple-cell

box concrete section. An arch truss madeof steel tubes was first erected with the

help of temporary cable stays. This steel

arch was designed to be embedded in the

concrete section and was used as a form

support for theconcrete arch, which was

cast segmentally from both abutments

toward the span centre. The concrete deck

is 23m wide and 140m above the normal

water level of the Yangtze River, and it

consists of precast T-beams resting on

vertical spandrel columns.

Cable-stayed bridges

The first major cable-stayed bridge to be

built in China was the Nanpu Bridge over

the Huangpu River in Shanghai, which

opened to traffic in December 1991. Its

main span of 423m was the longest in

China at the time of its completion. The

same team of engineers and contractors

went on to design and build another cable-

stayed bridge, the Yangpu Bridge, also over

the Huangpu River in Shanghai. It took

them just 29 months to design and build

this second bridge which had a span of

602m and was the worlds longest cable-

stayed bridge when it opened to traffic in

September 1993. This bridge opened 16

months before the 856m span Normandy

Bridge, even though it began construction

later.

It is interesting to note that these bridgeswere all designed and built by the Chinese

themselves with only DRC Consultants,

which merged with TY Lin International in

1995, as a special consultant to the owner,

the designer and the contractor.

China currently has the worlds second

longest cable-stayed bridge, the Sutong

Bridge in Jiangsu Province, not far from

Shanghai. It crosses the Yangtze River near

Suzhou. The main bridge has a main span of

1,088m with side spans of 300m and 100m

and a roadway width of 30.5m. It was the

worlds longest cable-stayed bridge when it

opened to traffic in 1997.

Suspension bridges

As previously noted, half of the 20 longest

span suspension bridges in the world

today are in China. Considering that China

only built its first long-span suspension

bridge, the 888m span Humen Bridge in

Guangdong Province 17 years ago, the pace

of construction has been remarkable.


9/60

INNOVATIVE TECHNOLOGYFOR BRIDGE CONSTRUCTION

+39 0432 60 79 [email protected]

Deal HeadquartersPozzuolo del Friuli(Udine) Italy

DEAL

For over 20 years we have been operating on a global scale, providingour clients with a full set of innovative and customized solutions.Thanks to our highly trained and qualified personnel, we are ableto supply specialized equipment for bridge and viaduct construction,as well as the highest levels of associated engineering servicesand technical assistance.

With the recent acquisition of TENSA - Italys leader in Post Tensioning,Stay Cables, Bearings, Expansion Joints and Antiseismic Devices we have significantly improved and expanded the range of our productsand services, in order to find even more comprehensive solutionsto our clients challenges.

RELIABILITY EXPERTISE DEDICATION RIYADH METRO PROJECTKINGDOM OF SAUDI ARABI


10/60


LONG-SPAN BRIDGES

Since that time, China has built many

long-span suspension bridges. The worlds

second longest suspension bridge, the

1,650m span Xihoumen Bridge in Zhoushan

was opened to traffic in December 2009.

Almost all long-span suspension bridges

have a steel box girder with an orthotropic

deck and have been produced exclusively

in China by Chinese fabricators. Likewise,

the wires for the main cables are also

manufactured in China and both air

spinning and prefabricated strands have

been used for the installation of the main

cables in those suspension bridges. Because

of the plans to continue building many

more long-span bridges, the industry was

willing to invest in new equipment and

learn new technologies. At the current

time, China probably has the most modern

steel fabrication facilities in the world; the

steel components of the new San Francisco

Oakland Bay Bridge in California, USA,

including the girder, the tower and the

cables were all fabricated in China.

Worth mentioning are a few smaller

suspension bridges in mountainous areas:

the 1,176m span Aijai Bridge in Hunan,

completed in 2012; the 1,088m span

Balinghe Bridge in Guizhou, completed in

2009, and the 1,196m span Longjiang Bridge

in Yunnan, which will open to traffic in 2016.

In these cases, because transportation

through mountainous terrain can be

difficult, a long-span bridge across the

entire valley is sometimes the best solution.

As well as the challenge of supply of

materials, the construction of a suspension

bridge over such a mountainous area poses

two major difficulties; erection of the lead

strand for the catwalk and erection of the

main girder. Unlike construction of a bridge

over water where the lead strand can be

carried by a barge from one tower to the

other, the same solution is not possible in

the mountains where it would be caught

by trees and rocks along the way. For theLongjiang Bridge, the lead cable was carried

from one end of the bridge to the other

end by a drone; in Xihoumen Bridge by an

airship, and in Siduhe Bridge by a rocket

which was provided by the military.

The girders of most suspension bridges

are erected by raising the segments from

a barge, but again this is not possible if

the terrain underneath the bridge is not

accessible. So, a new method was developed

for the Aijai Bridge. Firstly, a temporary rail

system was attached to the suspenders at

the girder level once the main cables and

all suspenders were in place. The segments

were then pulled along this rail system one

by one from the work platform at the tower

to their final position, until the entire girder

was completed.

China has built a large number of self-

anchored suspension bridges, although

most of them have spans at the shorter

end of the spectrum. They are suitable for

sites with poor soil conditions which are


11/60


LONG-SPAN BRIDGES

not good for building anchors. However,

the Pingsheng Bridge in Foshan, which was

completed in 2006, has a main span of

350m, and was the longest self-anchored

span in the world until 2013, when the new

east span of the San Francisco Oakland

Bay Bridge with its 385m-long main span

was opened to traffic. A year later, this was

overtaken by another Chinese bridge, the

420m span Huanghe Bridge in Zhengzhou,

Henan. Nevertheless, the Pingsheng Bridge

and San Francisco Oakland Bay Bridge

spans have only single towers, while the

Huanghe Bridge has two.

This record is set to be broken again in

the near future, as a record-breaking self-

anchored suspension bridge designed by

TY Lin International and Smedi is currently

under construction the Ergongyan Bridge

in Chongqing. This bridge is being built

next to an existing suspension bridge with

a 600m span, and for aesthetic reasons,

the new suspension bridge will also have

a 600m span. The ideal solution would

have been to build the new structure as

a traditional suspension bridge. However,

the soil conditions at the site were not

reliable enough to be able to securely

anchor the main cables, hence the client

decided to build a self-anchored suspension

bridge even though the main span will be

rather long. The towers are now underconstruction and the girder will be erected

using temporary stay cables. Once the

girder is in place, the main cables will be

installed and the load of the girder will be

transferred to the suspenders, after which

the stay cables will be removed.

Partially cable-supported girder bridges

A further development on the extradosed

bridge concept has recently been developed

in China for medium-span bridges; the

partially cable-supported girder bridge.

The process involves first designing the

structure as a girder bridge, which does not

have sufficient capacity to carry all of the

loads; this is supplemented by the forces

from the cables. Cables can be provided as

a suspension system, a stay-cable system

or from an arch rib. The system ensures

that the capacity of the girder and the cable

system are both fully exploited. It may look

similar to an extradosed bridge, but the

basic premise of an extradosed bridge is

that it is a girder bridge with post-tensioning

tendons raised above the deck to gain more

eccentricity. The cables are designed as

prestressing tendons with higher allowable

stresses, and they must have a relatively

flat inclination and the bridge towers

must be relatively short. A partially cable-

supported girder bridge does not have these

restrictions and the cables are designed as

stay cables.

The difference between a cable-stayed

bridge and a partially cable-supported girder

bridge is the function of the girder and

the cable system. In a traditional cable-


12/60


LONG-SPAN BRIDGES

stayed bridge, the cables are designed to

carry all the loads from the girder and the

capacity of the girder is only there to resist

local bending moments and axial forces.

Therefore the girder of a cable-stayed

bridge can be made very flexible, often with

a span to girder depth ratio of more than

150 or even 300, as in case of the ALRT

Skytrain Bridge in Vancouver, Canada. As

a rule of thumb, the span to girder depth

ratio for a girder bridge is around 20. For

many medium span bridges, the span to

depth ratio is often in the range of 25 to 45;

the girder itself can carry a large proportion

of the loads so the cable system is only to

carry the load that the girder is not able

to carry. Thus the required capacity of the

cables and the towers is much less than

that in a traditional cable-stayed bridge.

In the case of the Sanho Bridge, for

example, the cables carry only 50% of the

total load. This means a saving of 50%

of the cables and tower compared to a

conventional cable-stayed bridge.

The first partially cable-supported girder

bridge was the Sanho Bridge in Shengyang,

China, which was completed in 2008 and

has two spans of 100m.

The longest partially cable-supported

girder bridge is the Dongshuimen Bridge

in the city of Chongqing which was opened

to traffic in 2014. It has a 445m-long

main span and the girder is 13m deep

to accommodate transit trains on the

lower deck. It is located at the tip of the

peninsular where the Jialing River meets

the Yangtze River. The client wanted a

bridge that was prominent and beautiful

to serve as a landmark, but the design had

to minimise any obstruction of the view

of the city. The design of this partially

cable-supported girder bridge, takes full

advantage of the carrying capacity of such

a deep girder with its span to girder depth

ratio of 34, so fewer cables were required,

which makes the bridge even more

transparent. It has a sister bridge on the

other side of the peninsular, the Qianximen

Bridge, which was also designed as a

partially cable-supported girder bridge.

Over the last 30 years, China has built

many new bridges and with its population of

1.4 billion and its boom in construction, this

trend looks set to continue.

Man-Chung Tang is chairman of the board

of TY Lin International

LONG MULTIPLICATION

In recent years, many multi-span cable-

supported bridges have been designed and

built in China, including the Taizhou Bridge,

the worlds largest multi-span suspension

bridge (see page 15)and the Jiashao Bridge

(right), which is the largest multi-span cable-

stayed bridge.

Jiashao Bridge crosses Hangzhou Bay in

Zhejiang Province and is a six-tower cable-

stayed bridge which has five main spans each

428m long, and side spans of 200m. It is the

largest multi-span cable-stayed bridge in the

world and has a deck width of 55.6m.Compared to a traditional cable-stayed

bridge, the multi-tower version has a lower

vertical stiffness under live load, and hence

this needs to be improved by increasing the

size of the tower, increasing the stiffness of the

deck or adding auxiliary cables; none of these

options was practicable for the Jiashao Bridge

so alternatives had to be developed.

An x-shaped bracket was designed to

support the deck in plan at the towers and a

rigid hinge in the middle of the bridge releases

the temperature-induced load and longitudinal

displacement, hence reducing its impact on the

towers, while constraining rotation, deformation

and shearing displacement of the bridge deck.

One of the other major challenges for the

Jiashao Bridge was design of a maintenance

gantry for the twin box-girder deck; a traditional

system could not be used due to the obstruction

caused by the brackets at the towers, and the

rigid hinge at the centre of the main span. By

design of a special gantry, the number of units

required was reduced from 20 to just four.

China Foto Press/Getty Images


13/60

Cable stayed bridge, Marchetti viaduct, Ivrea (Italy)

YOUR CHALLENGES,

OUR SOLUTIONS.

tensainternational.com


14/60


LONG-SPAN BRIDGES

Four decades on from the advent of

the aerodynamic box girder bridge

deck on the Severn Bridge in the

UK, the impact of wind loading is still

one of the most critical factors in the

design of long-span bridges. But more recent

influences such as new procurement routes,

and the introduction of high-strength materials

also have an impact on the process.

Wind effects continue to be the governing

factor in the structural design of long-span

bridges, and more advanced testing rigs

and advanced computational methods are

being used nowadays to better mitigate the

aerodynamic instabilities, agrees Ender

Ozkan, a technical expert at Rowan Williams

Davies & Irwin. Another area of interest for

aerodynamic performance is the retrofit of

existing long-span bridges. Bronx Whitestone

Some of our longest-span bridges have been around for several decades now, and to alarge extent the technologies and engineering know-how of these structures are tried andtested. Lisa Russellexplores the influences on long-span bridge design today, and thechallenges of our ageing structures

Bridge is a good example where engineers

took advantage of the retrofitting to improve

the aerodynamic performance and breathe

new life into an ageing structure.

But the definition of a long span is

often the subject of discussion within the

engineering community, as Aecom vice

president Barry Colford pointed out in his

keynote at last years European Bridge

Conference in Edinburgh, Scotland.

In terms of numbers there are around 220

cable-supported bridges throughout the

world with spans greater than 300m; the

majority are either suspension bridges or

cable-stayed bridges and there is almost an

equal split in numbers of each of these two

main types.

As might be expected, it is economics

at the construction stage that is driving

the long-span bridge market and at spans

between 150m and 1,000m, cable-stayed

bridges now appear to be the preferred

option for most clients and engineers,

said Colford in his paper. Even in the USA,

where the development and use of cable-

stayed bridges has lagged behind Europe,

the cable-stayed form seems to be gaining

in popularity. Whether the industry wants

to continue to push the envelope out and

build cable-stayed bridges of 1,200m span

or more remains to be seen. Both forms of

cable-supported bridge have advantages and

disadvantages, he says. Recent problems

with corrosion of main cables may have

dented confidence in suspension bridges,

but Colford believes that the success of

dehumidification retrofit projects could

reverse this.

Spanning the future


15/60


LONG-SPAN BRIDGES

Chacao Channel Bridge is a flagship

project for Latin America - though onethat is still some way from coming to

fruition. It will be the regions the first multi-

suspension bridge with spans longer than

1,000m; the three-tower crossing will have

main spans of 1,155m and 1,055m.

At present, the client Chiles Ministry of

Public Works is in the process of reviewing

the final design. Construction is due to start

soon and the target is for the bridge to come

into operation in 2020.

The project has had a long gestation and

has been talked about for decades as part ofthe plan for a road to link the whole of the

American contintent, from Alaska to south of

Chile.

A scheme to build the bridge under a public-

private partnership was cancelled in 2006,

mainly for financial reasons. The project was

then re-evaluated during 2011-2012 from both

economic and technical standpoints. The

decision was taken to use traditional funding to

build the bridge for a maximum cost of US$740

CHACAO CHANNEL BRIDGE, CHILE

New forms

Chinas Taizhou Bridge, which opened in

2012, was first three-tower, two-main span

continuous suspension bridge system. The

structural behaviour of this type of system is

different from that of a conventional two-towersuspension bridge system, says Robin Sham;

cable slip at the saddles must be prevented

under all loading conditions, which leads to

conflicting demands at the central tower. A

flexible tower would help prevent cable slip but

would be ineffective in the control of girder

deflection; while a stiff central tower would

make it hard to prevent cable slip, although

it would improves deflection control of the

girder. The main reason for adopting the

three-tower form is that it enables very large

distances to be crossed, with only the minimal

number of bridge supports, Sham says. Oneof the challenges at Taizhou was that the

superstructure construction for a three-tower

suspension bridge system is much more

complicated than that for a two-tower system,

particularly in the main cable erection, main

girder erection and bridge geometry control.

Another different form of cable-supported

bridge is currently reaching completion in

Turkey. The final deck segment was raised

into place in early March of a hybrid cable-

stayed suspension bridge that is being built

north of Istanbul over the Bosphorus Straits;

a concept developed by Michel Virlogeux andT Engineering. The Third Bosphorus Bridge

officially called the Yavuz Sultan Selim Bridge

is being built by a joint venture of Astaldi and

IC Ictas and has 1,408m main span far longer

than the world record for a traditional cable-

stayed bridge, the 1,104m-span Russky Bridge.

The new bridges A-shaped towers stand a

million, including associated work such as

access roads.

The government signed a contract with

a joint venture of OAS, Hyundai, Systra and

Aas-Jakobsen in February 2014. Chile is one ofthe countries most affected by earthquakes,

making the project particularly challenging.

Not only is the bridge in a highly seismic

region, but also there are strong winds,

high tides and fast currents to address all

significant issues for construction. Both cable-

stayed and suspension bridge options were

studied before concluding that a suspension

bridge would offer many advantages, including

in terms of seismic behaviour.


16/60


LONG-SPAN BRIDGES

LOOKING AFTER OLDER BRIDGES

Many of todays challenging issues for bridge engineers come

from looking after old structures. In the years to come, Cowis

Tina Vejrum expects to see more projects to replace decks on

existing suspension bridges, following Canadas original lead with the

Lions Gate Bridge and now the ongoing Macdonald Bridge project.

I think there is a new market there with interesting challenges, she

says. A number of such bridges are reaching the end of their service

life, she says. Fortunately on a suspension bridge we can replace the

deck its a lot easier than for a cable-stayed bridge. Limiting closure

times is a key issue, as too is maintaining the aerodynamic stability in

the interim phase where the bridge is not fully connected and has two

different cross sections.

Another issue is deterioration of the main cables of suspension

bridges. Following successful use elsewhere, dehumidification is

being discussed for a number of US bridges including the George

Washington, Anthony Wayne and Benjamin Franklin. And in February,

the Delaware River & Bay Authority awarded American Bridge a

US$33.6 million contract to install a dehumidification system for the

main suspension cables on both structures of the Delaware Memorial

Bridge.

Dehumidification on main cables has passed the tipping point

in the USA, believes Aecoms Barry Colford. What has convinced

owners (and me) are the results from acoustic monitoring of the

UK bridges following application of dehumidification. These are

of course confidential and sensitive but owners are likely to be

aware of them through the International Cable Supported BridgeOperators Association, he says. It not only the results from acoustic

monitoring that have increased confidence in the effectiveness

of dehumidification. The results of internal inspections post

dehumidification have been very encouraging, Colford adds.

Hydrogen embrittlement needs moisture to generate hydrogen ions

and of course corrosion needs moisture and oxygen. If we can stop

moisture from getting into cables then we can potentially stop both of

these things happening, he says. The whole ethos is to make sure that

the service life of the cables matches the service life of the bridge. I

do think that dehumidification is the only way that we can be given

some assurance that this will happen. We now know that painting initself doesnt stop moisture getting into cables. We also know that

oiling doesnt appear to work either.

Aecom has been working on the dehumidification of the two

Chesapeake Bay Bridges and the scheme is now up and running. The

cables have dried out really well, says Colford.

Novel solutions involving complex surgery can also be required

when long-span crossings age, but some of the issues may not become

apparent until work begins. A recent project at the Humber Bridge has

highlighted the need for the client, designer and contractor to work

closely together to address any unexpected challenges on site. It has

also demonstrated some of the potential difficulties of using the new

higher-strength steels.

The Humber Bridge opened in 1981 and its 1,410m-long suspended

main span held the world record until 1997. The ends of the deck

boxes at the towers and anchorages were supported by pairs of steel

A-frames to allow free longitudinal movement of the deck boxes undertraffic and other effects, and providing horizontal restraint under wind

loading.

Routine inspections had raised concerns over a lack of articulation

and wear, so a scheme was designed by Arup for the Humber Bridge

Board, to replace the 3.8m-high A-frames with vertical pendels and

wind-shoes (Bd&e issue no 73). Owners of similar long-span bridges

are likely to have to contend with similar issues in the coming years,

says Spencer Group deputy managing director Richard Burgess.

His firm won the contract and completed the work in 2015, without

needing to close the bridge.

High-strength steel, grade S690 had been specified to reduce

the element sizes in the limited space available. But we found that

we couldnt meet the weld strength requirements with that steel,

says Burgess. When we dropped down a grade we got a far more

compliant material it was more weldable and still met the strength

requirements for the bridge, he says.

As a result, engineers believe caution is needed over the use of such

steel in bridges, where demanding fracture toughness requirements

may be coupled with the heightened risk of hydrogen embrittlement.


17/60

LONG-SPAN BRIDGES


record-breaking 322m-tall and its 59m width

will accommodate an eight-lane motorway

and two railway lines (Bd&e issue no 80)

It is an innovative structure, not only

because of its hybrid design but also because

the cables are the biggest ever installed on a

bridge, explains Erik Mellier, technical director

of Freyssinet, which designed and installed the

cables. Another notable feature is the use of

1,960MPa strand. It is the first time that we

are using such a high-strength strand, he says.

We have celebrated the biggest stay cable

ever installed in terms of length and size, says

Mellier. The longest of the cables are 597m

long, and have 151 strands. Compact cables are

being used, to reduce the drag.

The company has taken advantage of its

earlier work at Russky Island. It was a good

thing to have done before, because we could

take all the experience we had accumulated

there and adapt it to this project, says Mellier.

The initial challenges were in the design


18/60


LONG-SPAN BRIDGES

of the system, which had to be upgraded

compared to the standard. We carried out a

quite significant testing campaign, with fatigue

tests both in Germany and Chicago, says

Mellier. In addition, the bridge is quite flexible

and so there were issues during the design

stage about deformations and fatigue of the

cables. A special test was carried out, looking

at the behaviour of the cable under highdeflections.

Looks matter

Every long-span bridge is the result of

countless decisions - but some of those

decisions naturally have a far more profound

impact than others. The choice of procurement

method is one of the most fundamental,

affecting everything from the type of bridge

to how much influence the contractor and the

eventual maintenance team will have on what

it is made from and how it is built.

Procurement choices can also govern

the degree of receptiveness to innovative

approaches, whether involving the use of the

latest high-strength materials or by looking

for better ways of addressing issues such as

vulnerabilities.

But on all too many projects, price turns

out to be the only thing that matters in the

end, says Poul Ove Jensen, bridges director at

Dissing & Weitling. He is surprised that there

is so little focus on the appearance of major

bridges, particularly as they have an enormous

impact on the visual environment, much more

than buildings.

It is also surprising because clients seem

fully aware of the power of bridges as symbols;

in any project brief these days there is a clause

saying that the bridge must be a landmark, a

signature structure or an icon. Therefore its

very disappointing that at the end of the daythey just take the cheapest one, he says.

The client isnt even necessarily saving much

- if any - money. As far as were concerned,

there is no real relationship between cost and

lets call it beauty, he says. There is no reason

why a cheap bridge cant be a beautiful bridge.

There are many great bridges being built

around the world - but also quite a few

mediocre and some outright ugly ones, he

feels. The reason for this is not lack of talented

bridge designers, but often that clients are

not prepared to do what it takes, or dont

understand what it takes, to achieve the

intended result. The procurement method is

often the problem, Jensen feels.

The decline in the traditional approach

of completing design before construction

tenders are invited has been accompanied by

a corresponding increase in formats where the

contractors team is given responsibility for

much of the design. In design and construct

tenders, the bidders often see no reason to

make an effort because they assume only the

price matters - and all too often they are right,

he says. But in fact we can usually save them

money, he adds. For instance, this might come

from input such as reducing the concrete

quantities for the bridge.

Our main problem as architects is that

architecture is still considered an add-on to

bridge design, says Jensen. Yet in working with

engineers, no-one can see where the architects

work stops and the engineers begins; it doesnt

matter who came up with which idea we

always work as a team, he adds.

Balancing different demands in procurement

causes much debate, including the extent

to which you prescribe details, while leaving

sufficient opportunity for achieving value.

Client-based designs with construction-only

contracts do still happen, particularly in

some regions such as the Middle East. These

days, markets such as the USA or Europe

tend to go down the design and build route,

or public-private partnerships, says Stuart

Withycombe, who is CH2Ms director of major

crossings. How far you take the definition

drawings determines how much room you

leave for choice in terms of design, he adds.

If you want to be fairly protective of what

your output looks like then I think there is

justification for provision of a high level of

definition. But in other areas, maybe less so.

As well as appearance, the choice of

procurement method naturally has aconsiderable effect on who pockets any

savings that arise from value engineering. In

design-bid-build, savings arising from changes

that are accepted by the client may be shared

50:50 between client and contractor. But in

design-build, the contractor will simply seek to

put in the lowest price possible; all the savings

from the innovations therefore go to the

owner. At the same time, the concern is that

the owner may not get exactly what it wanted,

adds Marwan Nader, senior vice president at

TY Lin International.

However the use of definition designs is

starting to open up a new option for clients

in this regard, enabling them to lock-in the

appearance they want from the start. The new

Champlain Bridge in Montreal, Canada also

known as the New Bridge for the St Lawrence

is a current illustration. We ended up with a

definition design that was mandatory for the

bidders, explains Jensen. The Oresund Bridge,

which opened in 2000, was an early example

of this process, which is still only rarely used.


19/60

Better Bridge Solutions,from Beginning to End

2015 Bentley Systems, Incorporated. Bentley and the B Bentley logo are either registered or unregistered trademarks or service marks of Bentley Systems, Incorporated or one of its direct or indirect wholly owned subsidiaries. Other

brands and product names are trademarks of their respective owners. CS4337 12/15

Join the worlds top engineering consultancies and experience the satisfaction of delivering

safe, sustainable bridges on time and on budget. Achieve the highest level of real-time team

collaboration using Bentleys bridge information modeling software for the lifecycle of your bridge

project. Making informed decisions using the right data at the right time is critical to your success.

Were ready to help you build and maintain a better bridge.

Only Bentley can take you there.

www.bentley.com/BridgeInformation

Comprehensive Software for Designing, Building,

Maintaining and Inspecting Bridges of All Sizes.


20/60

Some see such an approach as beneficial,

others less so, feeling that it does not really

engage the creativity and resourcefulness of

the private sector. There can also be situations

where the ambitions of the architect ambitions

and the engineer dont really converge.

In Montreal, client Infrastructure Canada

was determined that the new bridge should

meet local expectations of a landmark bridge.

However, the project has an exceptionally

tight time schedule, particularly because

of the urgent need to replace the existing

bridge, which is in poor condition. A design

competition would have delayed the 2018

target completion. Use of the mandatory

definition design was a good solution, Jensenbelieves; it would have been impossible

to describe the architectural treatment,

proportions and so on sufficiently well in

words. The owner effectively had a guarantee

that it would get what was envisaged.

The public-private partnership agreement

with the government of Canada was won

by Signature on the Saint Lawrence Group,

which includes designer TY Lin International.

The aggressive schedule could never have

been achieved under a design-bid-build

environment, according to Nader. What the

client is getting is the best of both worlds, he

says. The project can meet the schedule, and

will be the bridge that was envisioned.

The Mersey Gateway in the UK (see page 42)

took an intermediate approach, partly using

the planning process to provide that definition,

says Withycombe, with some rules for what the

structure would look like. That took a high-

level view that nevertheless was very careful in

terms of how it defined visual quality, he says.

Were getting better as designers in


LONG-SPAN BRIDGES

terms of making things look better but its

not just how it looks its making sure it

works better as well, says Withycombe.

Aspects such as durability and choice of

materials are important. Its important to

fix the requirements so that you dont rule

out contractors coming along with their

most creative and best ideas for how to

build it. Contractors bring important areas of

innovation to the project.

This influence also extends to maintenance:

concession projects run for perhaps 30 or 35

years and clearly the structure needs to be in

a certain condition when handed back to the

client. This means designing for a particular

measure of performance 30 years from now,or risking expensive repairs before handover.

There have been changes in our world

because of the advent of PPP. says Mike

Cegelis, senior vice president at American

Bridge. There is a much greater focus on

the operational and maintenance costs of

components of the bridge than there was in

former times.

There is increased interest in health checks

for the bridge, particularly as the cost of

instrumentation falls. It is very fashionable to

equip all your bridges with all kinds of sensors,

says VSL International group technical

officer Max Meyer. But there is no point in

collecting extensive data unless it can be used,

he stresses. Adding value involves helping

clients to come up with a system that gives

meaning to the data and enables maintenance

interventions to be well planned.

Checking for vulnerabilities

Risks such as accidents and the potential

of terrorism have a significant impact

for the long-span bridges that are often

critical infrastracture links and the choice of

procurement method can also affect how such

risks are addressed.

At the advent of privately-funded bridges,

financial backers were mostly concerned with

the seismic risk. Earthquakes had certainly

been considered before then, but it had not

been such an overriding issue, says TY Lin

International senior vice president David

Goodyear. The same is now becoming true for

vulnerability assessments, he says.

Someone financing a project for several

decades needs to weigh up risks and revenue

implications, not just of terrorism but of all

kinds of major incidents - perhaps a tanker

catching fire. My personal belief is that

there is a lot of good thinking generated by

having private financing step in front of public

financing, because with private financing there

seems to be more ownership of the funding

stream, says Goodyear.

Blast protection is increasingly a key issue

for long-span bridges, though this tends not

to be widely discussed in public for fear of

raising awareness about vulnerabilities. At the

same time, increased attention is being paid

to the issue of fire protection both in service

and during construction. Various incidents

have made owners more concerned about

the potential consequences of fire affecting

a main suspension cable, hangers or staycables. In one instance a few years ago, a truck

caught fire by the low point of a main cable of

new Little Belt Bridge in Denmark and direct

lightning strikes of bridges such as the Rion

Antirion Bridge in Greece, which damaged

a cable and a similar incident in Korea have

raised this as an issue. Cable and hanger

suppliers are developing systems to provide

some fire protection.

We are beginning to see a requirement in

design, reveals Tina Vejrum, vice president

of international bridges at Cowi. Replacing

hangers or stay cables is one thing, but would

be a different matter if the main cable of a

suspension bridge was affected, she says.

Meyer is aware of five or six cases of

fire damaging cables on ong-span bridges,

including a recent one at a bridge in China

where fire broke out when welding was taking

place inside a tower. Nine cables were lost,

snapping one after the other; luckily the sites

tower cranes were able to drop water into the

tower from above to put the fire out.


21/60


LONG-SPAN BRIDGES

The Post-Tensioning Institute has

acknowledged the risk of fire and has

formulated test requirements. Details of

fire resistance qualification testing were

among the significant additions and updates

introduced in its 2012 edition. If you want to

supply a system you need to be able to pass

this test, says Meyer.

One of the key questions to address on a

project is what level of protection is really

necessary. Once the bridge is in service,

tankers pose a particular risk and Meyer

suggests that a rule of thumb might be to

take the protection to double the height of the

vehicles that will be crossing the bridge.

It is not only heat that poses a risk: cold and

in particular the build-up of ice are potentially

damaging. High-profile cases such as Canadas

Port Mann Bridge have highlighted the

dangers and cable companies are developing

prevention or removal technologies.

The devastating tsunami of 2004 highlighted

a further risk that major bridges can be

exposed to. Awareness of disaster prevention

was heightened in the aftermath, points out

Aecom director Robin Sham, the companys

global leader of long-span bridges. This has

fed into projects such as the Second Penang

Bridge, where a study of the likelihood of a

tsunami event and the resulting soil liquefaction

phenomena was carried out. The bridge,

which opened in 2014, consists of precastsegmental concrete marine viaducts and a

475m-long cable-stayed bridge. The study

sought to determine the risks and magnitudes

of tsunami-generated waves on the bridge, says

Sham. A simulation was then calibrated with

records to allow a predicted wave height to be

accommodated in the bridge design.

Advanced materials

There is correlation between advances in

materials and increases in maximum span

length over time, says Nader. But such

increases have now tapered off, he feels. In

my opinion, we are now on the cusp of starting

to look at ultra-light high-strength concrete

and what that will bring to the equation. It is a

major factor when spanning longer distances.

I dont think at this point that somebody is

going to dream up structural systems that give

us the ability to go longer - its going to have to

be through the materials, he says. Ultra-high-

strength steel, fibres and ultra-light high-

strength concrete will all play their parts.

A difficulty with high-strength materials

arises in relation to codes and standards, says

Vejrum. At the moment we cant go higher

than the grades we are using. For instance,

manufacturers can produce 2,200MPa steel

but this is far outside codes that only allow

values of perhaps 1,860MPa or 1,960MPa.

There is a similar situation for high-strength

concrete; it all boils down to who takes

responsibility. Without the backing of codes,

its difficult to get the materials introduced as

standard on projects, she says; consultants

wouldnt take the responsibility if the client

doesnt want to.

Perhaps it is more likely in the meantime

that such materials find a home on PPP

projects where the contractor is responsible

for subsequent of maintenance. This could

be a likely way forward, says Vejrum, as the

contractor will benefit from a saving on initial

costs and would deal with any subsequent

issues. However, agreement would also be

needed with the independent checkers about

going outside the codes.

Introducing innovations is certainly

becoming more difficult, feels Mellier, partly

for reasons to do with issues like CE marking

and norms. I believe that most clients are

increasingly reluctant to be the first, he says.

You really need large projects, such as the

Third Bosphorus Bridge, in order to move

forward. The technology can then be used onsmaller projects, as clients are less reluctant

once someone else has demonstrated that

it works. They can also take confidence from

the fact that the larger schemes are closely

examined by top consultants.

Advanced materials like high-strength

steel are not necessarily straightforward to

use. Issues can arise when using this kind of

material under high tension in bridges exposed

to chlorides and water. For example American

Bridge has had to deal with high-profile failures

of a small proportion of the tension rods on

the self-anchored suspension span built as part

of the new East Span of the San Francisco-

Oakland Bay Bridge. There have also been

some rod issues on other projects.

Such materials are now part of the bridge-

building world, says Cegelis, and they solve a

lot of other issues in an economical manner.

But we are now highly dependent on the

success of this material. It has obviously

been proven in a test environment that it can

meet the stresses that are imposed on it but

the question is whether it can withstand the

environmental attack.

Samples of any new material tested in the

lab are checked over by the manufacturer

in tremendous detail, points out Cegelis. But

fabrication of these one-off test pieces is not

the same as for general production and normal

handling on site in the real world.

Such elements may have their benefits but

American Bridge has certainly become quite

wary about them. Cegelis observes that the

company asks a lot more questions about jobsthat will use them. However, he regards the

issues as part of a natural process - inherent

problems have to be overcome whenever


22/60

We launch your projects e

CIMOLAI TECHNOLOGY SpA

Via dellIndustria e dellArtigianato,17 - 35010 Carmignano di Brenta (PD) Italy - Ph +39 049 9404539 - Fax +39 049 [email protected] - www.cimolaitechnology.com


23/60

technology advances.

Meyer too is seeing a move to go for higher

strength steel than the current 1,860MPa:

there are fabricators who want to push this to

something like 2,200MPa. The steel is harder

to produce - and more expensive - but for the

big bridges, wind is more of a controlling factor

and there is definite interest in keeping the

diameters of cables down, he says. However,

the product would need to be economical,

which may not be possible if the volume is not

there.

Patenting ideas

The long-span bridge engineering fraternityhas traditionally been very open with regard

to sharing details of innovations developed for

projects. Deciding what to patent is difficult.

We are patenting technology but we are

being quite careful about it, says Matt Carter,

Americas long-span bridge leader at Arup.

We are not going down the line of patenting

everything in sight.

One idea on which Arup does have a patent,

jointly with GS Engineering, involves earth-

anchored cable-stayed bridges. The system

enables thinner steel plates to be used for

very long spans. We felt there were good

arguments for cable-stayed bridges up to the

1,400m kind of range, and we felt that the

technology that really works well at that range

was to build partially earth-anchored cable-

stayed bridges, says Carter.

But publishing rather than patenting was

the choice for an innovative idea that was

developed at the time of bidding for the Izmit

Bay Bridge (see page 30), which Arup didnt

win. The concept involves a way of seismically


LONG-SPAN BRIDGES

TYPE TALK

What counts as a long span naturally depends on the type of the bridge. Acrow Bridge

recently supplied two bridges to a flood-damaged area in the Himalayas. The bridges were

customised with modular components to address local conditions and had clear spans of

60m and 80m. Such bridges can be operational in days, with minimal construction machinery and

using unskilled labour, says Acrow Bridge president Bill Killeen. In remote areas such as this, building

a modular steel bridge on site is often the best option, since constructing a conventional bridge of a

long length in-situ is most likely not feasible due to challenging topography, he says. Substandard

road conditions also make it difficult to transport heavy highway construction equipment or materials

to site. In contrast, the components for the Acrow structures were shipped in standard ocean

containers, which were then loaded onto compact trucks with a length of 6.5m.

isolating the anchorage of a suspension

bridge. Arup toyed with trying to keep the

technique as secret as possible though the

information had been included in the bid or

patenting it. But at Arup were not trying to

patent too much construction technology,

says Carter. We are a relatively patent-free

industry. We dont want to be a market leader

in taking us to a place where engineering

consultants are suing each other for patent

infringements. Instead, the decision was

taken to publish. He regards it as very positive

that the sector promotes a collaborative

environment, where people want to discuss

and share the work theyve done.

Technology

As bridge engineers design ever longer spans,

they typically depend on highly sophisticated

analysis models to use in the process. Vanja

Samec, global director bridges at Bentley

Systems, points to the issues involved for large

prestressed concrete and composite bridges

built using the incremental launching or free

cantilevering methods. The challenge is to

model accurately the erection process, while

considering different construction stages,

time-dependent behaviour, and the required

pre-cambering in order to achieve the design

shape once construction has been finished,

she says.

However, different challenges face engineers

when designing ultra-long-span bridges, such

as stay cable or suspension bridges with

high pylons and slender steel or concrete

decks. Here the challenges are mainly related

to optimising the stressing sequence of

the cables to the geometrically non-linear

behaviour of the structure, and to dynamic

problems such as wind-induced vibrations

and seismic events. It is natural that wind-

load effects would be greater on longer span

lengths of cable-supported bridges, she says.

These phenomena include vortex shedding

and the lock-in, across-wind galloping and wake

galloping, torsional divergence, flutter, and

wind buffeting.

Another area of IT development is in 3D

printing. Its going to change our industry in

a very big way, predicts Nader. Being able to

go from the computer to printing the bridge

would bypass a major part of the contracting

process. It may not happen within our lifetimes,

but could happen someday.


24/60

www.acrow.com

[email protected]

+1.973.244.0080


25/602016 Acrow Corporation of Ameri

For over 60 years, Acrow has been creating and restoring transportation lifelines under extreme

circumstances. In the spectacular foothills of the Himalayas, pilgrims make the annual trek to a Temple at

3,700 meters. Damaging floods cut off the route to the temple. Acrow supplied a clear span modular bridge

with components customized for local conditions. Installed in a matter of days, with minimal construction

machinery and unskilled labor, locals are able to make the pilgrimage again.


26/6026 www.bridgeweb.com LONG-SPAN BRIDGES SUPPLEMENT 2016

LONG-SPAN BRIDGES

HLOGALAND BRIDGE, NORWAY

Anew suspension bridge with

distinctive A-shaped towers and an

unusual cable arrangement is taking

shape over the Rombak Fjord near Narvik in

northern Norway.

Hlogaland Bridges 1,145m main span will

make it one of the longest in Europe, though

it is certainly not among the widest of the

worlds major suspension bridges as the

main spans steel box girder deck measures

just 18.6m across. It is also notable for its

A-shaped towers, the form of which has

governed the unconventional arrangementof the cables and hangers. As a result, the

bridge will be the longest in the world with

a spatial cable system: its main cables will

follow an oval shape in the horizontal plane

and the hangers will be slightly inclined in

the vertical plane.

Client for the scheme is the northern

region of the Norwegian Public Roads

Administration, Statens Vegvesen. The

bridge is typical of Norways crossings of

deep and wide fjords, in that traffic levels are

relatively low and so it will carry just a single

traffic lane in each direction, as well as a3.5m-wide walkway.

The towers have been designed very much

with aesthetics in mind. What we always

try to do is to take advantage of the special

conditions at the site and in this case it was

natural for us to choose an A-shaped tower,

says architect Poul Ove Jensen, bridges

director at Dissing & Weitling. The choice

suited the requirement for an attractive

structure, but decisions arent taken for

aesthetic reasons alone, he stresses. Design

should take account of a sites specific

requirements, rather than trying to invent

some dramatic forms, which often lead tovery contrived results. In this case a long

span bridge with an extremely narrow deck

it was quite a logical concept.

It is not a solution that would work

everywhere. For a conventional suspension

bridge, it would be difficult to have A-shaped

towers because of the very wide deck, says

Assad Jamal, chief project manager for

international bridges at Cowi.

At the start of design, members of the

team went to visit the site. By the end

of the week, we had the concept, recalls

Jensen. An H-shaped tower didnt look very

good, given the tall height and narrow width

needed; and a central tower between traffic

lanes was out of the question with the two-

lane road. The design team quite quickly

came to the conclusion that the A-shape was

right.

Two separate contractors are building the

bridge, with Sichuan Road & Bridge Group

responsible for the steelwork deck

Norways low trafficvolumes and localtopography have

led to creation of astunningly slender

structure


27/60

www.freyssinet.com

Follow us on:

NEW STRUCTURES

Cable-stayed structures

Prestressing

Construction methods

Structural accessories

REPAIR

Bridges and tunnels

Buildings

Water civil engineering

structures

Industrial structures

Historic buildings

by Freyssinet

Repair

Yavuz Sultan Selim Bridge

Turkey


28/60


LONG-SPAN BRIDGES

and cables and NCC for the concrete.

By March 2016, construction of both of the

concrete towers had been completed, and

the catwalk installation, which will take aboutthree months, had just begun. Installation of

the prefabricated main cable is due to start

at the end of July.

The tower design has dictated the layout

of the rest of the structure, in particular the

unusual spatial arrangement of the cables

and hangers. The two main cables meet at

saddles on a narrow support on the top of

the towers, splaying out at the centre of the

bridge. As a result of this alignment of the

main cable, the bridges hangers are slightly

inclined. In terms of stability of the bridge

subjected to traffic load, this has minor butbeneficial effect in regards of wind stability,

says Jamal though it did mean that

additional load cases had to be considered.

Having the A-shaped towers poses extra

challenges for installation of the cable

system; a special construction sequence

is needed to obtain the correct shape,

beginning by allowing the two main cables to

hang vertically during air spinning. Initially,

there will be a single common catwalk

between the two main-span cables.

The next step will be to displace the main

cables horizontally using an hydraulic strutsystem to create the oval shape, with struts

at 16m centres. The struts need to span

approximately 16m at the centre of the main

span, and they need to be able to telescope

outwards by using a hydraulic system,

explains Jamal.

The hangers can then be installed and the

deck erected, before the struts are removed.

The saddles are at the top of the towers,

and the shape of the towers means that the

saddles are very close together. As they are

so close together, there is an influence on

how the loads are distributed between theside span and the main span cables: where

a conventional suspension bridge tower

will twist for uneven main cable loading

in the main span, this is not the case for

Hlogaland Bridge. The towers do not twist,

which means that the loads of the back span

cables are shared evenly.

The ratio of span length to tower height

above deck for the bridge is 1:9; the ratio of


29/60

LONG-SPAN BRIDGES

LONG-SPAN BRIDGE SUPPLEMENT 2016 www.bridgeweb.com

main span length to the distance between

the cables is 90, while typical values for

suspension bridges are in the range 55-

60, explains Jamal. This combination of

a slender bridge with a long main span

posed considerable design challenges in

order to fulfil the requirement of ensuring

aerodynamic stability at 63m/s at bridge

deck level. The aerodynamic stability was

verified through numerical analyses and

wind tunnel tests; this showed a critical wind

speed of 68m/s.

The bridges box section deck is arranged

with a slope of 15.8 of the lower inclined

side plates relative to the horizontal bottom

plate, says Jamal. Wind tunnel tests carried

out in smooth flow proved that there will beno vortex-induced vibrations, thus saving the

potential costs of installing and maintaining

any mitigation measures.

Each tower is topped with a towerhouse; a naturally-ventilated structure

designed to enclose them the cable saddles

and give extra protection. They will also

be an architectural feature; their internallighting will be the only strictly non-

functional feature on the bridge, admits

Jensen.

! " " # $ % &

' $ # " ! ! ( $ " ) ! # * +' $ # " ! ! ( $ " ) ! # !

, - - - ./ % 0

! " " # $ % &

' $ # " ! ! ( $ " ) ! # * +' $ # " ! ! ( $ " ) ! # !

, - - -


30/60


LONG-SPAN BRIDGES

Anew bridge with one of the worlds

longest suspension spans is nearing

completion in Turkey. Izmit Bay Bridge,

which has a 1,550m main span, is being built

by IHI Infrastructure Systems and Itochu.

The team was given notice to proceed in

September 2011 and the bridge is set to open

in May this year a very short period for such

a major crossing.

The project had been on track for

completion in the first quarter of this year, but

suffered a setback last year when the catwalk

collapsed in March just as the contractor was

preparing to start erecting the main cable.

Luckily bad weather had halted work that

day and no-one was injured; the catwalk was

completely reconstructed and ready for use

by August.

The bridge is in a region that is seismically

very active and where a major earthquake

occurred on the North Anatolian fault in 1999.

Seismic issues have placed considerable

additional demands on the design.

Deck erection began at the start of this

year with the erection of three 51.2m-long

segments at each of the towers. A floating

crane was used for installation of the initial

segments at locations including the towers

and the ends of the side spans, with the

remaining deck segments positioned by a

lifting device mounted on the main cable.

Detailed design of the bridge has been

carried out by Cowi, with Dissing & Weitling

as the project architect. CH2M performed

the independent design check. Steel has

been used both for the main towers and the

One of two major bridges currently being built in Turkey isa long-span suspension bridge which forms part of a new420km-long motorway in the north of the country

IZMIT BAY BRIDGE, TURKEY

deck of the new bridge. The 235m-tall towers

have two legs and two cross beams; and the

legs measure 7m by 8m in cross section at

the base. The suspended deck is a single,

orthotropic box girder that is 30m wide and

4.75m deep and has a 2.8m-wide inspection

walkway attached to each leg.

The main cables on the main span have

been formed from 110 prefabricated parallel

wire strands each made of 127, 5.91mm-

diameter cable wires with a breaking strength

of 1,760MPa. The main cable on the side

spans has two extra strands of the same

size. Hanger ropes are of parallel wire strand,typically formed of 133, 7mm-diameter wires

with a breaking strength of 1,760MPa. They

are connected to a cable clamp at the top and

hanger anchorage at the bottom.

The side spans flanking the 1,550m main

span are each 625m long, giving a total

suspended deck length of 2.8km, which is

continuous between the two side-span piers.

A key design change was made early in

the project following ground investigations

by Fugro that showed a potential fault at the

planned location to the south anchorage. This

led to the anchorage being moved 138m to a

safe zone, reducing the main span from theoriginally planned 1,688m.

The structure is a central part of the

420km-long Orhangazi-Izmir motorway

project, which is being developed by Nomayg,

a consortium of six companies. The bridge will

carry the new link across the Sea of Marmara

at the Bay of Izmit in northern Turkey.

Read our full feature about Izmit Bay Bridge in

Bd&e issue no 83


31/60

byDCTowersDonauCity

KSPJrgenEngelArchtitekten,

Krebs&K

ief

erInternational

forces in motionMAURER AG|Frankfurter Ring 193 | 80807 Munich/Germany

Phone +49.89.323 94-0 | Fax +49.89.323 94-306 | www.maurer.eu

SOCAR TOWER,

ASERBAIDSCHAN

Job Description: Prevention of hori-

zontal accelerations of the flame-

shaped 200 m high structure, caused

by wind and earthquake.

Project scope:One MAURER Tuned

Mass Damper MTMD with a mass

of 450 tons, plus MAURER HydraulicDampers MHD which dampens at

0.32 Hz and a stroke of +/ 400 mm.

Including a monitoring system for dis-

placements, forces and accelerations.

DANUBE CITY TOWER,

AUSTRIA

Job Description: Reduction of the

horizontal acceleration of the struc-

ture caused by wind and earthquake

at a high rise building of 220 m height,

to generate sufficient comfort.

Project scope: Two MAURER ad-

aptive hydraulic dampers with a

response force of up to 80 kN and+/ 700 mm stroke, which dampen

the 300 ton mass-pendulum. Inclu-

ding a monitoring system for displace-

ments, forces and accelerations.

MOSQUE ALGIERS,

ALGERIA

Job Description: The third biggest

mosque in the world requires an in-

novative seismic protection, with a

design life of 500 years.

Project scope:246 nos. sliding isola-

tion pendulum bearings SIP with a ro-

tational hinge (design specification3 % dynamic friction and 2,400 mm

effetive radius), as well as 80 nos.

MAURER Hydraulic Dampers MHD

with a response force of 2,500 kN.

SIGNATURE BRIDGE,

INDIA

Job Description:Structural protection for

the new landmark in Delhi, displaying

a 150 m high pylon with asymmetrically

arranged stay cables.

Project scope:38 nos. MAURER MSM

Spherical Bearings, of this two pylon

bearings which have to support a verti-cal load of up to 23,000 tons. Moreover,

eight rocker bearings will accommodate

17,500 kN tensile forces each from the

stay cables and transfer these loads into

the foundation.

Structural Protection SystemsSTRUCTURAL BEARINGS | EXPANSION JOINTS | SEISMIC DEVICES | VIBRATION ABSORBERS| MONITORING


32/60

DYWIDAG Post-Tensioning Systems are known for their superior load-carrying

performance, durability and simple design. For decades, they have been renowned for

their extraordinary versatility and reliability.

DYWIDAG Post-Tensioning Systems employ high-quality corrosion protection methods

significantly contributing to the longevity of structures.

Visit us at

Bauma 2016Hall A2, Booth 339

Local Presence Global Competence

DSI DELIVERING SUPPORT & INGENUITY

www.dsi-posttensioning.com

North America, USA

www.dsiamerica.com

South America, Brazil

www.dywidag.com.br

EMEA, Germany

www.dywidag-systems.com/emea

APAC / ASEAN, Austral ia

www.dsicivil.com.au

Supplying Solutions to the Construction Industry

Approved Quality On Time Delivery Excellent Service

150

YearsofServic

e

Abraham Lincoln Bridge, Louisville, KY, USA


33/60


QUEENSFERRY CROSSING, UK

A

landmark cable-stayed crossing

is in its final year of construction

alongside two other famous bridgesover the Firth of Forth near Edinburgh in

Scotland. Design and construction of the

new Queensferry Crossing began almost five

years ago and the bridge is on track to be

completed by spring 2017.

The new bridge will take the record for

the worlds longest three-tower cable-stayed

bridge and it will also be the UKs tallest

bridge. Queensferry Crossing will itself

provide reasons enough for people to visit

the area when it opens next year - but it also

stands alongside one of Europes longest

suspension spans, the Forth Road Bridge,

and close to the historic Forth Bridge, which

carries railway traffic.

Forth Crossing Bridge Constructors,

a joint venture of Hochtief Solutions,

American Bridge International, Dragados

and Morrison Construction, is responsible

for designing and building the cable-

stayed bridge which will create a new link

between South Queensferry and North

Queensferry when it opens.

Including the north and south approach

viaducts, the bridge has a total of 14 spans,three concrete single-leg towers which

are on the centre-line of the transverse

cross-section, two planes of stay cables

anchored along the centre of the structure

and a composite steel and concrete deck

superstructure.

The three bridge towers reached

full height at the end of 2015, marking

a key milestone for the project team.

The reinforced concrete towers start at

bedrock nearly 40m below the water. The

middle tower is a height of 210m, while

the flanking towers are each 207m tall.

The towers are roughly rectangular in

cross-section, with the east and west sides

curved and the north and south sides

(where cable anchorages are located)

inclined. They were built in 4m sections

using climbing formwork, with a total of

54 lifts per tower. Each of the 54 tower

lifts had a slightly different profile, as the

hollow structure tapers from 16m by 14m

at the base to just 5m by 7.5m the top.

The towers are integrated onto structural

foundations through heavy verticalreinforcement and embedded into the

massive 25,000m3concrete bases formed

by using 1,219t steel caissons sunk to the

Forths seabed (Bd&e issue no 70).

The focal point of the visible bridge is the

cable-stayed section which makes up just

over 2km of the total 2,638m of the main

crossing, including the twin main spans of

650m supported by the three main towers.

The bridge has a multi-cell steel box girder

design with a composite reinforced and post-

tensioned concrete deck; a parallel strand

system is used to anchor the deck girders to

the towers.

Deck construction began with the erection

of temporary falsework at each tower to

accept four starter segments. The starter

segments contain more steel and concrete,

making them heavier, and so were erected

on the temporary falsework in order to allow

the concrete decks to be cast in situ. For the

rest of the units the typical segments

LONG-SPAN BRIDGES

The worlds longest three-tower cable-stayed bridge is reaching completion in Scotland


34/60

+44 (0)20 7973 6694

www.bridgeweb.com

[email protected]

Your bridge

specialist

SUBSCRIBE TODAY

THEDEFINITIVEPUBLICATIONFOR

BRIDGEPROFESSIONALSWORLDWI

DE | ISSUENO.70 |FIRSTQUART

ER2013 |WWW.BRIDGEWEB.COM

DARK

ARTSLIGHTING

LOWRY

AVENUEBRIDGE

7/26/2019 BDE

bde long span bridges supplement

Documents