Future Trends In design & construction of bridges

8/7/2019 Future Trends In design & construction of bridges

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FUTURE TRENDSFUTURE TRENDSININ

DESIGN & CONSTRUCTIONDESIGN & CONSTRUCTION

OFOF

BRIDGESBRIDGES

bybyShiv KumarShiv Kumar

Director/IRICENDirector/IRICEN


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IntroductionIntroduction

UnprecedentedUnprecedented developmentsdevelopments bothboth inin thethe bridgebridgetechnologytechnology asas wellwell asas towardstowards appearanceappearance..

Technically,Technically, veryvery longlong spanspan bridgesbridges cancan bebe builtbuilt withwithpresentpresent--dayday materialsmaterials.. SpansSpans areare becomingbecoming biggerbigger ee..gg..bridgebridge onon ChenabChenab riverriver inin JJ && K,K, oneone ofof thethe longestlongest archarchspanspan ((480480m)m) inin thethe worldworld.. (Fig(Fig..11))

ConsiderationConsideration ofof thethe entireentire lifelife cyclecycle justifyjustify drivingdriving thethespanspan upwardsupwards..

SocietySociety increasinglyincreasingly willingwilling toto paypay forfor thethe convenienceconvenienceandand aestheticsaesthetics ofof longlong spanspan bridgesbridges..

CableCable--stayedstayed bridgesbridges encroachingencroaching onon thethe typetype ofof spansspans

traditionallytraditionally associatedassociated withwith suspensionsuspension bridgesbridges.. ee..gg..LongestLongest cablecable stayedstayed bridgebridge constructedconstructed inin thethe worldworld ininJapanJapan (Tatara(Tatara 890890mm span)span).. (Fig(Fig..22))

11,,000000mm barrierbarrier breachedbreached byby StonecuttersStonecutters bridgebridge ininHongkongHongkong andand SutongSutong bridgebridge inin ChinaChina andand 11,,200200mm spanspanalreadyalready plannedplanned.. GrowthGrowth inin smallersmaller suspensionsuspension bridgesbridgeswithwith spansspans ofof perhapsperhaps 100100mm toto 500500mm..


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Emerging trends in the design andEmerging trends in the design and

construction of bridgesconstruction of bridgesArchitectural Appearance

Appearance plays a far greater role in bridge design

today than it did a few years ago.

Greater awareness of the importance of a bridge designthat properly fits its setting e.g. Bow String Girder

Bridge across Thane Creek in Mumbai region provides a

visual treat to the rail commuters. (Fig.3)

A client wants an artist to dictate the design, the architectto interpret, the engineer to make it work.

The wow factor can come with something that is both

original and simple in concept e.g. much-praised

Gateshead Millennium Bridge (Fig.4)


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construction of bridgesconstruction of bridges

Security hazard

Multi-hazard protection growing importance against

blasts and earthquakes.

Massive increase in armoury of tools to protect bridges.

Developments in areas such as understanding of seismic

activity, techniques for risk assessment, means of

predicting seismic response .Solutions envisaged like

wrapping columns with glass/carbon fiber, energy

absorbing devices, structural fuses to dissipate energy.

Earthquake not a force but a deformation. New concept

to provide sufficient capacity in deformation and allow

bridge to move instead of trying to resist force.


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construction of bridges (contd.)construction of bridges (contd.)

Increased Span

Developments in cable technology a key parameter to

increasing the span.

Significant progress made by reducing the size ofstrand systems ,adding features such as helixes around

the cables.

Damping important for long spans .Solutions such as

tuned mass dampers, cross-cables or aiguilles as usedon the cable-stayed Pont de Normandie bridge in

France. (Fig. 5)

Todays spinning equipment is competitive with

preformed parallel wire strand systems.


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.Taller Bridges

Equipment developed for handling and driving

piles of large diameter upto 4m and length more

than 100m.

Improvements in drill hole stability while drilling

huge diameter holes.

Use of large diameter piles made it possible to

position the pile cap further above the river bed.

Larger piles can have a long unsupported length

enabling the footing to be constructed far closer to

the water surface.


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Getting stronger

Introduction of a new material will only be successful

if a new concept of structure can be developed to use

that material e.g. use of stone to build arches. Steelmade long span trusses box girders possible. High

strength wires made suspension bridges possible.

Together with concrete by way of prestressed concrete

made long span concrete bridges possible.

Ultra-high performance materials intoduced such as

VSLs cementitious material Ductal which is nearer

steel than concrete.


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Precast Components

Pre-cast foundation, abutment, pier and superstructure

units enable construction of bridges not in years but in

months and weeks e.g. San Juan, Puerto Rico (Fig. 6)

erected from the ground up in just 21 consecutive hours

Lake Ray Hubbard Bridge in Dallas, USA used pre-cast

bent caps (Fig.7) for all the 43 pier caps reducing

construction time from 8-9 days to 1 day for each pier

cap(Fig.8)

Pre-cast units eliminate costly field formwork as well as

extend seasonal construction time.


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construction of bridges(contd.)construction of bridges(contd.)

New materials

Use of advanced composites started e.g. stainless steel .

Different types of applications for composites e.g. use in

post-tensioning, plates and strips, FRP decks, stay

cables, wraps to provide seismic protection and

enclosures to protect structures.

For rehabilitation also e.g. composite rods to replace the

top mat of steel reinforcement effectively increasing the

cover to steel.

FRP bridge decks gaining popularity in USA.


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Increasing durability

Increased durability being demanded e.g. plastic ducts.

Introduction of enhanced protection through use of

electrically isolated systems .

Change in the bridge deck design e.g. in the traditional

design, there would normally be some kind of supporting

structure generally topped by a concrete deck which

could easily be replaced but now in the modern bridge,the deck is part of the structure and holding it up ,its

replacement could become more complex and expensive.


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Conclusion

In India, so far one cable stay bridge constructed

spanning across railway track near Bangalore. (Fig.9).

Another one under construction at Chirayatand near

Patna.

Significant growth expected in demand for long span

bridges .


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Thank YouThank You


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(Fig. 1)


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(Fig. 2)


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(Fig. 3)


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(Fig. 4)


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(Fig. 5)


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(Fig. 6)


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(Fig. 7)


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(Fig. 8)


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(Fig. 9)

Future Trends In design & construction of bridges

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