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FINAL REVIEW OF THESIS ON

TECHNO-ECONOMIC ANALYSIS OF VIADUCT SYSTEMS OF DELHI

METRO

By Sanskriti Tiwary

Masters of Building Engineering & Management

School of Planning and Architecture, New Delhi

SANSKRITI TIWARY | BEM-539 | SCHOOL OF PLANNING AND ARCHITECTURE

Aim of the study is to arrive at the parameters and constraints leading to selection of different viaduct systems for elevated corridors for infrastructure.

Aim


Scope Cost, Constructability, Speed of construction and Site constraints of:

• Precast viaduct systems

• Cast in-situ viaduct systems

• Balanced cantilever viaduct systems

Limitations • Structural calculations and loading aspect

• Construction techniques for pile and pier

• Operation and maintenance

• Rail laying and alignment

• Electrical and drainage services

• Construction of metro stations


Viaduct ??!

Oxford Dictionary

A long bridge-like structure, typically a series of spans,

carrying a road or railway across a valley or other low

ground.

Cambridge Dictionary

A long, high bridge, usually held up by many arches,

which carries a railway or a road over a valley.


Viaduct System ??!

A viaduct system

comprises of a

deck resting on

pier caps which

transfer the load to

the pier and then

pile cap and piles. Piles

Pile Cap

Pier

Pier Cap

Deck


Viaduct Systems Studied

Category Viaduct Systems

Pre-fabricated Single Segmental U Girder

Segmental Box

Cast in-situ Single Segmental Box Girder

I girder and slab

Balanced Cantilever Extra-dosed Bridge

BCLC at Jasola-Apollo


Precast Viaduct Systems

It is a construction product produced by casting concrete in a

reusable mold or "formwork" which is then cured in a

controlled environment, transported to the construction site

and lifted into place.

Casting Yard

Transportation

Launching

Site


Single Segmental U Girder

• Precast Pre-tensioned deck

• Metro in Faridabad from Badarpur to YMCA Chowk

• Only in this system, the pier caps are also precast

• Two cranes of 400 ton and 330 ton capacity each are used to lift a 150 ton weight and 27 meter long U-girder


Segmental Box • Precast Post-tensioned deck

• Launcher- fixed point & variable point

• Site – Near Mayur Vihar over Yamuna & IP Extension

• The launched segments are aligned, glued and then the cables are tensioned and grouted.


Parameters

Single Segmental U

Girder Segmental Box

Inferences

A B

Length of

viaduct studied 12500 m 650 m

The length of A studied is twenty

times that of B

Cost per meter ₹ 3,03,200 ₹ 3,84,615 + ₹ 20,00,000

The cost per unit length of A is

less than half of B if assembling

and disassembling of launcher Is

considered

Speed of

construction

390.63 m /month

43.33 m /month

The speed of construction of A is

9 times that of B

Max. clear span 27 m 41.6 m The max. clear span achieved by B

is 1.5 times that of A

Depth of girder 1.85 m 3 m The depth of girder of B is much

more than that of A

Site constraints

The space below the

viaduct is accessible

for construction

activities

The viaduct is

constructed over a

flowing river, thus the

space below the

viaduct can’t be used

A doesn’t have the site

constraints that B has

Aesthetic

Requirements

Levelled smooth

soffit

Levelled soffit,

however joints are

visible between

segments

Comparatively A is aesthetically

much more appealing


₹ 6,92,308 ₹ 3,03,200

Single

Segmental U

Girder

Segmental Box

VO

LUM

E


Cast in situ viaduct is poured into site-specific forms and cured on site.

Cast In-Situ Viaduct Systems

Single Segmental Box Girder

I Girder and Slab


• Precast post-tensioned • This system is used only where the site conditions

demand • It can be considered a transition element

between different types of viaduct systems if there is a difference in the sizes of pier caps

• It is best suited for spans were precast deck is not possible and/or costly and/or launching is not possible

• It requires ground support for shuttering and thus cannot achieve greater heights.

Single Segmental Box Girder


• I girders are precast pre-tensioned, still this system is considered under cast in-situ due to the large amount of cast in-situ works it requires.

• The girders are lifted and rested on the pier caps.

• They are stitched together with cross beams and at the end by end diaphragms, cast in-situ.

• Slabs are casted over the girders.

I Girder and Slab


Parameters

Single Segmental

Box Girder

I girder and slab

Inferences

C D

Length of

viaduct studied 28 m 2770 m

Length of D is almost a 100 times

that of C as only a single span of C

was required

Cost per meter ₹ 4,00,000 ₹ 2,61,733 Cost per unit length of C is 1.5

times that of D

Speed of

construction 37.33 m /month 115.42 m /month

Speed of construction of D is 3

times that of C

Max. clear span 28 m 31 m The difference in max clear span is

3 m

Depth of girder 2.25 m 2.25 m The depth of the girder is same

Site constraints

A single span was

casted on site due

to the pier cap size

constraints

No such constraint

C can be casted on site if there is a

difference in the pier cap size on

both ends, but it requires support

from ground.

Aesthetic

Requirements

Levelled soffit,

however

shuttering marks

are visible

Shows I girder and

web from below;

no smooth soffit

Comparatively C is aesthetically

more appealing


• Balanced cantilever construction implies construction of cantilever segments from

a pier in a balanced fashion on each side until the mid-span is reached and a

closure known as stitch segment is made with other half span cantilever

constructed from the preceding pier.

• The fundamental of the design is building a bridge deck by succession of segments

where each segment carries the weight of the next segment. Each segment is

integrated with the previous one as soon as it is strong enough. Each segment

becomes self-supporting and also becomes a base for a new segment.

Balanced Cantilever Viaduct Systems


The Pragati Maidan viaduct is an extra-dosed railway bridge with a main span of 93 m.

The deck cross-section has a U shape, which permits a perfect integration of the metro

system in the superstructure. The extra-dosed cables are covered by a concrete beam

that allows considering them as internal pre-stressing. This beam also increases the

stiffness of the main span.

Constraints:

• Crossing of 5 railway tracks

• Sharp plan curvature

• Railway vertical clearance

• Impossible location of intermediate piers

• No possible interruption of the railway traffic

• Minimum span length of 93 m

Extra-dosed Balanced Cantilever


The balanced cantilever bridge with a hundred metre long span is between Okhla

and Jasola metro stations over the Indian Railways tracks on the Central

Secretariat – Badarpur corridor. The bridge is part of the 20.16 km-long under-

construction Central Secretariat-Badarpur corridor.

Constraints:

• Crossing of 5 railway tracks

• Sharp plan curvature

• Railway vertical clearance

• Impossible location of intermediate piers

• No possible interruption of the railway traffic

• Minimum span length of 100 m

Balanced Cantilever at Jasola-Apollo


Parameters

Extra-dosed Bridge BCLC at Jasola-

Apollo Inferences

E F

Length of

viaduct studied 196.3 m 250 m

The length of viaduct under study is

comparable

Cost per meter ₹ 6,62,252 ₹ 2,77,000 The cost per meter of E is twice as

much as that of F

Speed of

construction 21.81 m /month 41.67 m /month

Speed of construction of F is almost

double the speed of construction

of E

Max. clear

span 93 m 100 m

The max. spans achieved are

comparable

Depth of girder 1.5 m – 3 m 2.5 m Depth of girder is comparable

Alignment Curved with a radius

of 302 m

Curved with a

radius of 300 m

Alignment is also comparable

Site constraints Railway line is

passing from under

Railway line is

passing from

under

Railway traffic cannot be

obstructed

Workers 230 130

More workers were engaged in E

than F


Conclusion

Parameters

Single

Segmental

U Girder

Segmenta

l Box

Single

Segmenta

l Box

Girder

I girder

and slab

Extra-

dosed

Bridge

Balanced

Cantileve

r

A B C D E F

Greater Max Clear Span 1 4 2 3 5 6 High speed of Construction 6 4 2 5 1 3

Least Cost 4 1 3 6 2 5 Constraints Space constraint below the viaduct x 1 x x 1 1

Short viaduct (< 300m) x x 1 x 1 1

Long viaduct (> 300m) 1 1 x 1 x x

Aesthetic requirements 1 1 1 x 1 1 Viaduct at large heights (> 5m) 1 1 x 1 1 1

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Documents

sanskriti tiwary bem

architecture viaduct

architecture aim

b length of viaduct

architecture scope cost

construction site

speed of construction

pier caps