Chenab Bridge

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Chenab Bridge & Anji Khad Bridge

Chenab Bridge is an arch bridge under construction in India that spans the Chenab River between Bakkal and Kauri. The bridge will be 1,315 m (4,314 ft) long, with a 480 m (1,575 ft) trussed arch span 359 m (1,178 ft) above the river Chenab and a 650 m (2,133 ft) long viaduct on the Kauri side.^[1]

The bridge is part of several bridges and tunnels that comprise the Katra to Laole Section of the Udhampur – Srinagar – Baramulla Rail Link Project in Jammu and Kashmir. Another, smaller, arch bridge in the link will be the 657 m (2,156 ft) long, 189 m (620 ft) high Anji Khad bridge between Katra and Reasi.

The Chenab Bridge is scheduled to be completed in December 2009,^[2] and will then have the highest bridge deck above ground, surpassing the Millau Viaduct in France.

1 Introduction and Topography
2 Salient Features of Chenab Bridge
3 Special Considerations
4 Anji Khad Bridge
- 4.1 Salient features of Anji Khad Bridge
- 4.2 Special considerations
5 Footnotes
6 References
7 External links

[edit] Introduction and Topography

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The Indian Railways has undertaken a mega project of construction of a new Railway line in J&K state from Udhampur to Baramulla, which has been declared a national project.^[3] The alignment is a culmination of large number of Tunnels and Bridges which are to be implemented in highly rugged and mountainous terrain, with most difficult Himalayan Geology. The alignment crosses deep gorges of Chenab River near Salal Hydro Power Dam which necessitates construction of long span bridges. After lots of deliberations, the configurations of steel arches were found most suitable on account of aesthetics, economy, and availability of local expertise and construction materials.

The Chenab Bridge, 359m above river bed, will be the highest bridge in the world, and longest span for BG Rail line with arch span of 485 m. This bridge is in the most difficult part of the project which has been assigned to the Konkan Railway Corporation Ltd. Many experts throughout the globe based on the versatile and relevant experience have been involved in order to make this project a success.

National codes of India; Indian Railway Standards (IRS), Indian Road Congress (IRC) and Indian Standards (IS); have been supplemented with International standards; British Standards (BS), International Union of Railways (UIC) and Euro; as national codes were found inadequate for such large spans. The Quality aspect has been emphasized, as the quantum of fabrication and welding is colossal. Mostly indigenous material has been planned to be used where as for the design, international codes have been referred which makes the Quality Control work still difficult.

Regular painting of such bridges is an intimidating task. Hence a painting scheme has been developed having life over 15 years compared to 5 to 7 years (approx.) of life in most of the Indian Railway Bridges. The erection scheme for the Bridge is a project in itself where two pylons (about 130 m and 100 m high) are to be erected on either side of the river and two auxiliary cable cranes (Capacity 80T each) consisting of self propelled equipment will be running on the carrying ropes across these pylons.

[edit] Salient Features of Chenab Bridge

1. Total length of the Bridge : 1315 m
2. Contract amount : Rs.5120 Millions
3. Height of Bridge (river bed to formation) : 359 m
4. Main Arch Span : 485 m
(Span may vary (between 465 to 485) as per detailed design of foundation)
5. Total No of Spans : 17 Nos.
6. Concrete Pier/ Abutment : 13 Nos.
7. Steel Piers : 5 Nos.
8. Pier/Abutment Foundation : 16 Nos.
9. Concrete Pier Type : Hollow Rectangular
10. Deck Type : Inverted U-type steel deck
11. Deck Width
Viaduct Portion : 13.50 m
Arch Portion : 17.00 m
12. Max. Ht. of Steel Pier : 133.734 m
13. Max. Ht. of Concrete Pier : 49.343m
14. Max. Size of Foundation Viaduct Portion : 18x15x4.15 m
Arch Portion : 50x30 m
15. Type of Bearing : Spherical Knuckle Bearings
16. Track Provision : Two Track
17. Total Steel Fabrication : 25000 MT
18. Seismic zone : Zone V
19. Wind Velocity : 220 km/h (at deck level)
20. Geology of terrain : Slope along Katra side bank (South): 35 to 50 deg. Qazigund side bank: vertical to sub vertical

[edit] Special Considerations

The structural concept of bridge over river Chenab is a large span arch over the river with approach viaducts on either side. The proposed arch is a two-ribbed arch, fabricated from large steel trusses. The chords of the trusses will be sealed steel boxes, filled with concrete to assist in controlling wind-induced forces on the bridge. Another advantage of concrete filling is that internal painting will not be required. The boxes will be stiffened internally.

The numbers of bearings have been minimized, particularly on the approach viaduct, through the use of continuous construction. This is advantageous as it reduces the maintenance and inspection efforts and improves the riding quality. The viaduct piers are of concrete while the piers near the arch are in steel.

The design of major arch rail bridges requires considerations of a number of additional parameters, such as fatigue, global stability, second order effects, composite action, etc. It also requires that such a bridge is designed to achieve a consistent level of reliability for all load cases and that the design standards match the construction standards.

The Indian Railway Standards (IRS) is primarily intended for simply supported bridges with spans up to 100m (although these have been successfully used for higher spans up to 154m). The spans proposed for this bridge greatly exceed this limit and are continuous. In order to provide these additional features it will be necessary to augment the design with additional international codes and standards that provide suitable provisions to enable the designer to produce a safe design.

Following are some of the special features of structural design for the bridges.
1. Limit state philosophy of design has been decided to be followed as per BS codes.
2. Computation of wind load effects as per Wind tunnel tests
3. Site specific seismic spectra developed by Indian Institute of Technology (IIT) Roorkee.
4. Provision of Euro code 8 for ductility detailing of very tall and hollow rectangular RCC piers.
5. Provision of long welded rail (LWR) over the bridges and resulting force calculation as per UIC – 774-3R guidelines.
6. Blast resistant design has been used.
7. Design checking for Fatigue as per BS codes.
8. Deformation limits as per comfort criteria of UIC – 776-2R and UIC 776 -3R guidelines.
9. Redundancy provided in the structures, for lower level of operation during mishaps and against collapse in extreme cases of one pier failure.

[edit] Anji Khad Bridge

The alignment is a culmination of large number of Tunnels and Bridges which are to be implemented in highly rugged and mountainous terrain, with most difficult Himalayan Geology. The alignment crosses deep gorges of Anji-Khad near Reasi which necessitates construction of long span bridge. After lots of deliberations, the configurations of steel arches were found most suitable on account of aesthetics, economy, and availability of local expertise and construction materials.

Anji Khad Bridge, with main arch span 265m long at a height of 189 m from the Bed Level is perceptible. Many experts throughout the globe based on the versatile and relevant experience have been involved in order to make this project a success. National codes (IRS, IRC and IS) have been supplemented with International standards (BS, UIC and Euro) as national codes were found inadequate for such large spans. The Quality aspect has been emphasized, as the quantum of fabrication and welding is colossal.

The material procurement has been done as per IS codes where as for the design, international codes have been referred which makes the Quality Control work still difficult. Regular painting of such bridges is an intimidating task. Hence a special painting scheme has been developed having life over 15 years compared to 5 to 7 years of life in most of the Indian Railway Bridges

[edit] Salient features of Anji Khad Bridge

1. Total length of the Bridge : 657 m
2. Contract amount : Rs.2070 Millions
3. Height of Bridge ((river bed to formation) : 189 m
4. Arch Span : 265 m (Trussed Steel Arch)
5. Viaduct Span on Katra side : 80 m (2 x 28.41 + 23.18)
6. Viaduct Span on Reasi side : 312 m (8 x 30 + 3 x 24
7. Total Steel Fabrication : 7000 MT
8. Deck Width : 13.50 m
9. Seismic zone : Zone V
10. Wind Velocity : 189 km/h (at Deck Level)
11. No. of Foundations : 16 Nos.
12. Type of Foundation : Open Foundation
13. Number of Piers : 15 Nos.
i. Abutment - 01 No.

                ii. R.C.C Piers     - 11 Nos.

iii. Steel Piers - 04 Nos.
14. Number of Spans : 14 + 1 Arch Span
15. Type of Bearing : Knuckle Bearing
16. Number of Track : Single track at present at centre
(To carry 2 future Broad gauge tracks)
17. Centre to centre of Track : 5.5 m (with 1.5m wide footpath on either side)
18. Geology of terrain : On Katra Side bank slopes are steep and are vertical to sub vertical.

[edit] Special considerations

Aesthetic merit of the bridge has been considered and strong attempt has been made to bring a natural cadence to the site. The structural concept of bridge over river Anji Khad is a large span arch over the river with approach viaducts on either side. The proposed arch is a three-ribbed arch, fabricated from large steel boxes The chords of the trusses will be sealed steel boxes, filled with concrete to assist in controlling wind-induced forces on the bridge. The boxes will be stiffened internally. It is proposed to fill concrete inside the arch ribs to improve the structural performance. Another advantage of concrete filling is that internal painting will not be required.

The IRS is primarily intended for simply supported bridges with spans up to 100m. The spans proposed for this bridge greatly exceed this limit and are continuous. In order to provide these additional features it will be necessary to augment the design with additional codes and standards that provide suitable provisions to enable the designer to produce a safe design.

Following are some of the special features of structural design for the bridges.
1. Use of Limit state design method as per BS codes for steel design.
2. Computation of wind load as per Wind tunnel tests.
3. Site specific seismic spectra developed by IIT Roorkee.
4. Use of Euro code for ductility detailing of very tall and hollow rectangular RCC piers.
5. Calculation of long welded rail (LWR) forces as per UIC guidelines.
6. Consideration of Blast Load.
7. Design checking for Fatigue as per BS codes.
8. Deformation limits as per comfort criteria of UIC guidelines.
9. Redundancy provided in the structures.

[edit] Footnotes

^ Narayan, Laxmi (March 2006). "TECHNICAL PAPER ON ANJI KHAD AND CHENAB BRIDGES" (pdf). Advances in Bridge Engineering: 101–114. “Type of Bridge : Trussed Steel Arch (Arch Span = 480m)”
^ "J&K to have world's tallest bridge", TOI News, 2007-11-05. Retrieved on 2008-01-14.
^ Template:Title=Northern Railway Website: Official Page on the Kashmir Railway Project

[edit] References

Narayan, Laxmi (March 2006). "TECHNICAL PAPER ON ANJI KHAD AND CHENAB BRIDGES" (pdf). Advances in Bridge Engineering: 101–114. “Type of Bridge : Trussed Steel Arch (Arch Span = 480m)”