2006 iitk-urban transportation-infrastructure

Urban Transportation Infrastructure-Construction Techniques

Presented by-

Pravin Kolhe,MTech, Transportation System

Engineering,Department of Civil Engineering,

IIT Kanpur.

Overview of presentation

IntroductionConstraints during constructionPlanning for projectMaterialsTechniques for Urban Transportation Structure

Superstructure Substructure

PPT Downloaded from http://www.pravinkolhe.com/

1. Introduction

Urban transportation infrastructure involves large scale construction

There are various constraints.Need of innovative techniques for timely

completion.


2. Constraints during construction Space constraint Time constraint Utilities Environment Aesthetics Safety Economy


2.1 Space constraint Historical Places Existing structures Minimum

disturbance to traffic

Photo.1. Space constraintPhoto: http://www.civil.skanska.com/skanska/templates/page.asp?id=3359


2.2 Time constraint

Construction of new infrastructure is normally taken up when existing infrastructure is not sufficient to fulfill the demand.

Urgent need to start and complete the construction During the construction, the existing infrastructure is

strained further. So, timely completion of the project is important.


2.3 Utilities Infrastructure normally passes through densely

populated area. So, there are some utilities as

Water mains (Underground) Sewer lines (Underground) Telephone lines (underground or overhead) Power supply lines. (overhead)

These utilities should be diverted, which is time consuming and costly affair.

Many times, the utilities are not known till the starting of work.


2.4 Environment

Air and noise pollutionDue to slow moving vehicular trafficDue to construction activity


2.5 Aesthetics

Photo 2. Aesthetics of urban transportation infrastructurePPT Downloaded from http://www.pravinkolhe.com/

2.6 Safety

Accidents causes loss ofLifePropertyEnvironment


3 MaterialsPreferred materials-

BricksStonesTimberMetalsConcreteComposite


3.1 Bricks

• For small spans• Light Loads


3.2 Stones

• Old construction material

• For small spans• Time consuming• Light load


3.3 Timber

• Temporary Bridges• Less span and less load


3.4 Metal

• Speedy construction

• Large span• Heavy loads


3.5 Concrete

• Precast• Pre-stressed


3.6 Composite

Use of metal + Concrete


4. Techniques for ConstructionElevated structures are divided it to-

SuperstructureSubstructure

Fig. 3. Components of elevated structures


4.1 Techniques for Superstructure

Techniques-Span-by-span construction with precast girder.Precast post-tensioned segmental techniqueContinuous units on ground supported stagingCentral span by Cantilevering techniqueBalanced cantilevering technique


4.1.1 Span-by-span construction with precast girdersMost economicalPrestressed girders are

lifted from casting yard and transported to site on trailers

At site they are lifted and placed on pier cap by cranes.

Deck slab is then casted over these girders.


4.1.2 Precast post tensioned segmental techniqueSimply supported post-tensioned units of 2~3

m with epoxy bonded joints.For standardization of segments, cable profile

is made horizontal in the middle span.

Fig.5. Construction by Precast post-tensioned segmental technique


4.1.3 Continuous units on ground supported staging

At crossing, central span is more.So prestressed continuous units becomes

obligatory.In such case, central unit can be casted by

staging by diverting traffic


a) End spans are casted on staging

b) Traffic diverted and central span is casted on staging

c) Open to traffic.

Fig 7. Construction of continuous unit on ground supported staging

4.1.4 Central span by cantilevering techniqueEnd spans are casted on stagingCentral span is casted by cantilevering.When two cantilever meet, the stitch

segment is casted.


a) End spans are casted on staging

b) Cantilevering construction started from ends

c) Cantilevering construction completed from both ends.

Fig 8. Construction of central span by cantilevering PPT Downloaded from http://www.pravinkolhe.com/

d) Stitch segment is casted

e) Construction completed

Fig 9. Construction of central span by cantilevering PPT Downloaded from http://www.pravinkolhe.com/

4.1.5 Balanced cantilevering technique

Only end portion of end span is casted on staging

Remaining end span and central span is casted by balanced cantilevering.

When two cantilever meet, the stitch segment is casted.


a) End portion of end spans are casted on staging

b) Cantilevering construction started from ends in both directions

c) Cantilevering construction completed from both ends.Fig 10. Construction by balanced cantilevering


d) Ground supported staging at end spans

e) Stitch segment is casted

f) Construction completedFig 11. Construction by balanced cantilevering


Fig. 12. Construction by balanced cantileveringPPT Downloaded from http://www.pravinkolhe.com/

4.2 Techniques for SubstructureTechniques-

Self supporting cutting.Sheet pilesDiaphragm wallSingle cast-in-situ bored pile.Driven casted pileGroup of piles.Well foundation


4.2.1 Self supporting cutting

For shallow depth and hard soil, soil cutting is possible at self supporting slopes.


5.2.2 Using sheet pile

For higher depth &/or soft soil sheet pile are preferred.


4.2.3 Using diaphragm wallFor deep

cutting, diaphragm wall is most useful

These are installed prior to taking up the excavation work.

Generally, it is part of final structure


4.2.4 Cast-in-situ bored pile150 - 600mm dia to

20m deepAs a rotary auger

causes minimal vibration it is ideal for use next to buildings or underground services without destabilization.

Dewatering techniques can be used if water is present.

Fig 13. Cast-in-situ bored pile


4.2.5 Driven casted pile150mm - 600mm to

20m deepUsed on soft soils

overlay. Permanently steel

cased piles are driven with an internal drop hammer.

Suitable reinforcement is then added and the casing filled with concrete.

Fig 14. Driven casted pile


4.2.6 Group of piles Most of pile foundations

consists not of a single pile, but of a group of piles, which act in the double role of reinforcing the soil, and also of carrying the applied load down to deeper, stronger soil strata.

Fig 15. Group of piles


4.2.7 Well foundation.Used under very

heavy loads to be carried by soft soil.

Fig 16. Well foundation


Thank you(c) Pravin Kolhe, 2006

http://www.pravinkolhe.com/



2006 iitk-urban transportation-infrastructure

Technology

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