Fib Various Types of Structures for Namma Metro

8/11/2019 Fib Various Types of Structures for Namma Metro

1/34

1

BANGALORE METRO RAIL PROJECT

Some Interesting Construction features in Namma MetroViaducts and Stations.

Sudhir Chandra B.S.Director (Project & Planning), BMRCL.

INTRODUCTION

The burgeoning growth of population, vehicular traffic and advent of IT and electronic industries in thelast four decades in Bangalore, reminded the need for a Mass Rapid Transit System (MRTS) inBangalore as far back as in 1983. Several studies were undertaken including a World Bank study in1988. A Light Rail Transit(LRT) system on Public-Private Partnership (PPP), based on a feasibilitystudy by IL &FS, after fixing a private partner was also tried; but it failed to takeoff due to a variety ofreasons. The success of opening a few sections in Delhi by Delhi Metro Rail Corporation (DMRC)resulted in the award of a contract in 2002 to DMRC to make a DPR for a metro system in Bangaloreconsisting of two corridors and costing about Rs.5000 crores. DMRCs report in May 2003recommended two corridors, one East-West corridor from Byappanahalli to Mysore Road terminalupto Ring Road junction, 18.10 kms long and another North-South corridor from Yeshwantpur to RVRoad Terminal 14.90kms long a total length of 33 kms at a completion cost of Rs.4989 crores. GoIapproved the project in May 2006 at a completion cost of Rs.6395 crores meeting out the inflation in

the intervening period. Equity participation of both governments, GoI and GoK, was equal at 15%each. Total share of GoI was 25% and GoK 30% including subordinate debt and the balance 45%was the senior term debt. Further in 2010, GoI approved extensions of 5.60km on north toNagasandra and 3.70kms on South to Yelachenahlli on North-South corridor at a completion cost ofRs.1763 crores, making the metro net work Phase-1 in Bangalore, 42.30 kms long, at a completioncost of Rs. 8158 crores. On account of phenomenal increase in prices of cement and steel, buildingmaterials -especially sand-and fuel, the estimate was revised and Govt. of India approved the revisedcost of Rs.11609 crores on 4thOctober 2011.(Rs. 1 crore = Rs. 10 millions).

The Phase-2 of Bangalore Metro, 72.10 kms in length, consists of 61 stations( 49 elevated and 12underground) and the cost of the project is INR 264.05 billion( about 5.0 billion USD) It consists of

four extensions on the N,S,E & W of N-S and E-W corridors of Phase-1 and two new lines 18.8 kmsand 21.2 kms long. Except for a length of 14 kms, rest 58.1 kms is elevated. The Public InvestmentBoard(PIB) has approved the proposal and the Govt.of India sanction is expected shortly. It isplanned to be completed in 2019.


2/34

2

2. Salient features of the Project:

Gauge : Standard Gauge(1435mm) double line.

Design speed : 80 kmphCommercial speed : 34 kmph

Total length of lines : East-West corridor - 18.10kms

North-South corridor - 24.20kms

Total - 42.30kms

Elevated corridor - 33.50kms

Underground corridor - 8.80kms.

Total number of stations : At grade 1 (Byappanahalli)

Elevated - 32

Underground - 7(incl. common Majestic interchange station)

Centre to centre distance of tracks :

Elevated 4.20m Underground 15.04m (twin tunnels).

Station platforms:

Elevated : Side platforms, 4m wide generally.Underground : Island platform, 12 to 16m wide.Sharpest curve (horizontal) : 120m radius in main line in elevated corridor

200m radius in main line in underground corridor100m radius in depots and yards.

Maximum cant : 125mmMaximum cant deficiency : 100mmVertical curve radius : 1500 m (min)

Steepest gradient : 3.3% (permitted 4%)Percentage of curved track : about 40%Rolling stock : Modern rolling stock with Stainless steel body and air

conditioned automatic closing doors.

Motored axles - 67%

Axle load - 15 tonnes

Class of accommodation - One

Capacity of 3 car unit 975 Capacity of 6 car unit 2005.

Size: 20.80 x 2.88 x 3.80m high.

Maintenance facilities : E-W corridor - Baiyappanahalli depot N-Scorridor - Peenya depot

Train operations:

Minimum headway : 3 mins.

Design Phpdt (peak hour peak direction trips) : 40,100

Operating hours : 5.00 hrs to 24.00 hrs

Projected ridership : 19.7 lakhs by 2021

Financial Internal Rate of Return (FIRR) : 5.46%

Economic Internal Rate of Return (EIRR) : 24%


3/34

3

3. Construction features in brief:

3.1. Viaducts

Metro corridors are passing through one of the densest areas in Bangalore City. The roads

are narrow; at times it is hardly 14m wide. Immediately, alongside the road are the utilities

(water supply pipelines, sewers, communication cables, electric cables, etc) buried hardly

600mm below the ground. There is storm water drain thereafter with a foot-path on top of it.

Hugging on to the footpath are the shops or residences with or without setbacks and

compound walls. When the viaduct pier is located in the centre of the road, the road which is

already narrow becomes narrower still to the extent of the foot print of the pier. Hence in

narrow roads, the lateral dimension of the pier had to be kept to the minimum to affect the road

width least. So design of pier had to be suited accordingly.

Similarly, the superstructure girders were designed to suit the segmental construction with

launching girders (overhead and under slung) single cell, box shaped, deck type to support

both tracks (Up and Down). I girders were used as an exception.

Typical viaduct structure

3.2 Elevated Stations:

Design of elevated stations had to be done depending on the local conditions, road widths, foot

path widths available, etc. Broadly Station structures designed in Bangalore Metro Project can

be classified into two categories:

(i) Cantilever structure - Tracks, platforms & concourses are on single central pier.

Staircases/Escalators from concourse to platform have been housed in off road

structure. Station entry is also in off road structure. Off road structures provided are

connected through linking bridges to the station structure.


4/34

4

(ii) Portal structure- It houses entire station including staircases & escalators fromconcourse to platform. Only station entry staircases/escalators are on footpath or off

road.

4. Viaducts Construction details:

4.1 Nature of foundation Open individual footing,Strip footing,Raft,Pile

Open /Raft foundations are seldon used as the availability of rock at shallow depths is rare.

This is also limited to availability of hard strata at depths less than 4 to 5 meters. Beyond this

depth, pile foundations are adopted. The substrata consist of silty sand, sandy silt,

disintegrated rock and hard rock (230 to 300 mpa). For Viaduct, pile foundations, circular piles

of 1200mm dia have been used. The bearing piles capacity is taken as 500t and friction piles

capacity as 300t to 400t the lateral load capacity is taken as 20 to 28t depending on strata &

site constraints and conditions.


5/34

5

OPEN FOUNDATION :


6/34

6

RAFT FOUNDATION :


7/34

7

STRIP FOOTING :

PILE FOUNDATION :


8/34

8

PILES CASTED :

4.2 Sub structure Pier and Pier cap for Viaduct:

The pier width of 1.6m is chosen normal to traffic direction to minimize occupation of the road

foot print and least reduction in the carriageway.

4.2.1 Elliptical Piers:

Circular pier is the best shape for a pier- most efficient cross section. But since Bangalore

metro goes in narrow roads, the lateral dimension of pier should be reduced to have more

carriageway width. So, in the first reach elliptical pier was designed with the minor axis kept

square to the road and major axis parallel to the road. Since the pier is elliptical in shape, theshuttering for pier becomes cumbersome, costly and time taking. So in other reaches, it was

changed to Double-D shape, shutters for which is comparatively easier to make; Pier cap

shuttering is also not complicated. In the case of elliptical piers the pier cap shuttering is also

very complicated. All piers are having flutes (serrations) with horizontal bands in between.

This helps in easy tearing of bills pasted on piers by miscreants.


9/34

9

Elliptical Piers


10/34

10


11/34

11

Double D Pier:


12/34

12

4.2.2 Eccentric/ Inverted L-shaped Piers:

At certain locations, where the piers cannot be placed in the road lanes, as it becomes anobstruction, the piers are placed in the road median and eccentric piers are constructed, ie, the

box girder centre is eccentric wrt the centre of the pier. However, the maximum eccentricity is

limited to 1900mm.


13/34

13

4.2.3 Portal Piers:

Where eccentricity goes beyond 1.80m, eccentric piers are not preferred. But a Portal is

constructed with two legs and a beam on top to span the legs, which will support the Box

girder. In such a case, the rail level goes up compared to standard piers/eccentric piers.

4.2.4. Shuttering used for piers in both the above cases(4.2.2 and 4.2.3) are not interchangeable with

the standard circular piers shuttering, whereas the Double D pier shuttering are

interchangeable. Hence, the non-circular pier scores over circular pier in this respect.


14/34

14

4.3 Superstructure for Viaduct

Single cell, box type, segmental girder has been mostly used on viaducts. They are posttensioned. Blisters are left in 2ndand 3rdsegments for future pristressing, if required.


15/34

15

4.3.1 The standard viaduct span is 28m. Each segment is 3m long except the pier segments (first

and last which are 1.95m long). The 3m modules when taken out / added in from the standard

span make the spans 25m, 22m and 31m. On sharp curves (120m radius) shorter spans of

22m are used as otherwise there is uplift of bearings in larger spans.

4.3.2 At road junctions or while crossing rail tracks,etc non-standard spans, cast-in-situ, post

tensioned girders are used viz 41m,50m,66m on Bangalore Metro project. The 66m span only

one of its kind is on a 136m radius sharp curve crossing electrified railway tracks, a single cell

box girder, post-tensioned. To prevent uplift of the bearings, vertical prestressing with 96

strands, 7 ply is being done for both the piers. A dummy hole has also been left in each pier,

for future use, if need be.

4.3.3 The viaduct spans are designed as simply supported spans except for those at track cross

over and turnout locations where the slabs are designed as continuously supported over

girders.

4.3.4. Elastomeric bearings have been used for spans upto 31m and POT and PTFE bearings for

longer spans as well as spans carrying track cross-overs and turnouts.


16/34

16

ELASTOMETRIC ( UPTO 31M SPANS GENERALLY ) :


17/34

17

POT-PTFE ( FOR SPANS ABOVE 31 M , SHARP CURVES 120M RADIUS ,CROSSOVERS AND TURNOUT

SPANS)


18/34

18

5. Elevated stations Construction details:

There are two types of elevated stations in Bangalore Metro Rail.

5.1 Cantilever stations:

There is a central pier carrying the tracks; the concourse and the platforms cantilever out from

this pier. They are spaced 15 to 20m apart. It has limitations in that the cantilever length is

limited as otherwise there will be excessive deflections. Also resonance is to be specially

checked up. But it gives a very sleek and pleasant look. The diversion of utilities is minimized

in this configuration of stations. The concourse girders are I type (precast, pretensioned/post

tensioned) or Pi type (precast RCC). There are pier arms at concourse and platform levels to

support I type or Pi type girders. Platform girders are I type (precast, pretensioned/ post

tensioned, steel) or Pi type (precast RCC).

Track girders are I type posttensioned girders (4 nos) or U type pretensioned girders (3 nos).

U type girders are not suitable in the spans where the d.c. electric traction cables have to bebrought from the track level to the Traction substation in the station building at concourse level

as there is no space between the girders to puncture hole/slit through the deck slab. Hence,

in such spans, I-girders have been used as there is enough space available between the top

flanges of the adjacent girders for hole/slit to be made through the deck slab. They rest on

elastomeric bearings.

Roofing is supported on steel trusses. Galvalume sheeting of different colors with

polycarbonate sheets interspersed for adequate lighting is used. Sides of the platform to the

extent possible are kept open for good ventilation.

Station entry to concourse is provided in off road structures.


19/34

19

REACH - 2 (ALL SIX STATIONS): CANTILEVER STATION (EXAMPLE MAGADI ROAD).

SUPER STRUCTURE FOR TRACK SUPPORT : I GIRDER (POST-TENSIONED)


20/34

20

PLATFORM LEVEL AND CONCOURSE LEVEL PIER ARM DETAIL :


21/34

21

SUPERSTRUCTURE CONCOURSE SUPPORT : Pi - GIRDER (PRE-CAST RCC)

(SUPERSTRUCTURE PLATFORM SUPPORT : Pi GIRDER (PRE-CAST RCC)


22/34

22


23/34

23

ROOF STRUCTURE STEEL FRAME WITH GALVALUME SHEETING.

PLATFORMSUPPORT

TTGIRDERS

CONCOURSESUPPORT

TT

GIRDERS

DOUBLEDCOLUMNS

PIERARMSWITHLBEAMS

SUPPORTTHE

CONCOURSEGIRDERS

ANDPLATFORMGIRDERS


24/34

24

5.2 Portal structure stations:

Station structure consists of portals, generally three-legged, to span the road widths. The

other members and components remain more or less the same. Such structures have

been adopted in reaches R-1, 3b and 4a. The merit of this structure is that it is more stable

and the internal stair cases & escalators are within the main structure. With such aconfiguration, the land acquisition is minimum at the sides.


25/34

25

SUPER STRUCTURE FOR TRACK SUPPORT: I GIRDER (POST-TENSIONED)

SUPERSTRUCTURE PLATFORM SUPPORT: I GIRDER (PRE-TENSIONED)

SUPERSTRUCTURE CONCOURSE SUPPORT : I - GIRDER (PRE-TENSIONED)


26/34

26

6. Some unique design of Viaduct and Stations.

6.1 Special Curved span 66m flyover over Electrif ied Railway tracks (Cast-in-si tu):

The Northern line of Bangalore Metro from Peenya to Sampige Road station flies over theSWR Tumkur electrified main lines at Malleshwaram (Kuvempu Road). It is a skew crossing

with curvature of 136 mtrs radius. The span across the railway land is 66mtrs. It consists of a

single cell box girder, post tensioned. Due to the sharp curvature and long span, the outer

bearings are subject to uplift; replacement of bearings often over running tracks will be

difficult. To prevent uplift of the bearings, vertical prestressing was thought of in the beginning,

but was given up considering the durability, the need to have spare arrangements for

prestressing during service, if the need arises, as very limited periods will be available for

repairs, retrofitting, etc once the commercial operations are commenced.

CONCOURSESUPPORTIGIRDER


27/34

27

Salient Features:

OVERALL SPAN (C/C OF EXP JT) : 66M

RADIUS AT CENTRELINE OF ALIGNMENT : 136M

DEPTH OF THE BOX GIRDER : 4.0 M

WIDTH OF THE BOX GIRDER AT TOP : 8.8 M

WIDTH OF THE BOX GIRDER AT BOTTOM : 3.6 M

TYPE OF BEARING PROPOSED :POT-CUM-PTFE

MAX. NO OF AXLES ON THE SPANS : 13 AXLES / TRACK (OF 15 TONS)

TOTAL NO OF PRESTRESSING CABLES (LONG.) : 24 NOS OF 19 T 15

TOTAL NO OF VERTICAL PRESTRESS STRANDS : 95 NOS OF 15 DIA

HEIGHT FROM RAIL LEVEL TO PILE CAP TOP :13.7M (MAX)

OVERALL HEIGHT OF PIER : 8.82M (MAX)

PIER SIZE : 4M X 2.5 M

PIER CAP SIZE AT TOP : 4.9M X 4.5M

THICKNESS OF PIER CAP : 0.6 M ST + 0.9M VARYING

NO. OF PILES : 8 & 9NOS RESPECTIVELY.


28/34

28

6.2 Deepanjalinagar Station:

Deepanjalinagar station is the penultimate station on the Magadi Road-Mysore Road stretch of

E-W Corridor. The station is sandwiched between the ROB across the Mysore Bangalore SWR

lines and the National Highway to Mysore. The topography on either side of the station is

undulating and the formation is in deep cutting. It is also surrounded by three built up areasand an important temple just at the edge of the station which have to be saved and these

constraints make entire station (three legged portal structure) an indeterminate structure with

unequal spans. The portals have also unequal legs.


29/34

29

6.3 Some special features at stations:

6.3.1 Foundations : Mono Piles:

At times the extreme rows of columns go very near to the property line making construction of

multipiles and pile cap construction impossible. Mono piles of higher diameter 1600mm have

been used (normal piles are 1200mm diameter)

6.3.2 Floating columns:

Due to space constraints and shifting of utilities (sewer lines especially) not

becoming feasible, floating column concept has also been adopted.

MONOPILES (1600MMDIA)


30/34

30

6.3.3 Replacement of girders/bearings dur ing maintenance:

Generally elastomeric bearings are provided for all standard spans and at stations. POT and

PTFE bearings are provided for special spans greater than 31m and cross over spans. The

bearings have life of 20-25 years. Bearings have to be replaced in viaduct by lifting girders by

taking temporary block for train movement. In case of station, replacement of bearings will berequired only on the track girder where trains are moving. This can be replaced by opening the

rail fastening system and connection to the bearings and refitted after replacement of the

bearings. Other bearings of the stations at concourse are not subjected to heavy load thus

unlikely to be replaced.

6.3.4 Transition spans:

In the station lengths the track supporting structure is either I-girders or U-girders whereas the

viaduct in the approaches of the station consists of segmental box girders. Hence the first pier,

just after the station ends, is a transition pier on which from one side I or U girders of station

rest and on the other side the segmental box girder rests. As the depths of girders vary, thebearings are at different levels and the pier cap has to be meticulously designed to take care of

the extra moments due to the couple action. These transition spans are kept normally not

more than 20m in length.

FLOATINGCOLUMN


31/34

31

6.3.5 Electrostatic insu lating membrane:

As the mode of traction is 750 v dc, to prevent electrocution of passengers while alighting or

boarding the train (one hand being held against the coach and the foot being on the platform)

special electrostatic membranes are placed below the floor finish for a width of about 4 meters,

which acts as an insulating medium.

7 Stray current protection:

A special feature of this metro is that since 750V dc third rail system is used, there is the

problem of stray current corrosion which doesnt arise in other metro systems where AC

traction is used. We have to guard against it. Special measures have been adopted to

minimize the corrosion of neighboring utilities, of steel members, rebar of metro structures

which will otherwise weaken the structure and reduce its life. This has been done by inter

connecting rebars from the track level to the foundation bottom level of piers, columns, etc so

that they get earthed.

MAHATMA GANDHI ROAD STATION:


32/34

32

SWAMI VIVEKANAND ROAD STATION:

BYAPPANAHALLI STATION:


33/34

33

YESHWANTHPUR STATION:

VIJAYANAGAR STATION:


34/34

34

NATIONAL COLLEGE STATION

Conclusions:

Stations have been designed passenger -friendly, persons with disabilities- friendly (lifts and

tactile provision), etc. Bangaloreans, being especially aesthetic loving and connoisseurs, the

stations have been architecturally designed to give a pleasing look in the Bangalore sky line.

------A THING OF BEAUTY IS A JOY FOR EVER-----

Fib Various Types of Structures for Namma Metro

Documents

Transcript of Fib Various Types of Structures for Namma Metro