Bridge Rehabilitation in Remote Area
Bridge Rehabilitation in Remote Area
Bridge Rehabilitation in Remote Area
--------------
BY
R.K. DHIMAN
Abstract
Bridges are generally designed for 100 years but there are cases where
distress has been observed prematurely. The reason for such distress may be poor
design, faulty construction and lack of maintenance. Each component of the bridge
has to play a vital role during serviceability period. In case any distress noticed, same
should be attended to in a planned way. Bridge construction in remote area is a
challenge due to number of factors like variation in foundation strata, space
restriction for launching superstructure, restricted weather conditions, highly
seismically active area. In case of natural calamity like cloud burst, earthquake,
flashflood distress in bridges has been observed leading to disruption in traffic. At
many location the distress to such bridges has been handled based on local
resources to make bridges traffic worthy. Generally distress are dislocation of
bearing, excessive scour around pier and washing away of approach to bridge proper
and some time collapse of superstructure. Once the distress is noticed a detailed
observation are taken along with proposed corrective measures. Opinion of the
bridge expert is also taken wherever required to address the problem in shortest
possible time. Bridge rehabilitation can be better handled if the engineer are fully
conversant with the sequence of construction involved in a particular bridge. There
are many cases where systematic approach and analysis simplified the rehabilitation
process and bridges are now serving well.
Border Roads had done rehabilitation of number of such bridge in remote area
departmentally Case studies of Ranga, Kunifer, Deo and Bhinni bridges has been
discussed in this paper.
Email : d_himan12@yahoo.com
1.0 Introduction
Bridge rehabilitation is a challenge for bridge engineers in remote area due to various
logistic problem. Remote area also devoid of latest technology and trained manpower. Few
bridges are located in high altitude and snow bound area. Infact if the engineers responsible
for maintenance of bridges are aware about the construction sequence of bridges, then
rehabilitation became easier. Major cause of distress is nonfunction of bearing, expansion
joint, excessive scour around pier, approach washed away. Rehabilitation of Ranga Deo
Kunifer, and Bhini Bridge has been discussed in this paper.
Border roads had constructed number of bridges in remote area, there had been
major problems during construction of foundation and superstructure. Foundation strata
posed big challenge due to heterogeneous mix underneath, flash flood and deep gorges
posed challenges for constructions of superstructure.
(a) There are number of bridges where approach washed away or structural
damage making bridge unfit for traffic, this is due to non compaction of approach or
due to non consideration of impact of high current on U/S of approach. Bridge where
such danger has been observed are Siji bridge on Lekhabali along road,Dimwo
bridge on Silapather -Pasighat road, (In Arunachal Pradesh and Assam).( Fig 1&2)
FIG 1&2 APPROACH WASHED AWAY AND DISTRESS IN CAP BEAM LOCATION
(i) River training works on Zero side and to confine the flow into the designed
channel only. However this proposal had demerit that there could be more scour
around piers.
(ii) To add additional single span of 67.00 m, in that case it was not possible to
accommodate the load on abutment A2 and also due to vertical clearance
consideration as the depth of superstructure (67.00m) is more than the existing
girders of 40 M span (Total 120 = 40 x 3).
There was a change in the flow pattern of the river and most of the discharge started
flowing through one span of the bridge due to silting observed on the u/s right side with the
continuous flow of water towards the left bank. There was a sizable damage to the abutment
consequent to which the reinforcement got exposed. The box return made towards
approaches on Agartala side got exposed and water started flowing below the foundation of
box return. This caused extensive damages to the bridge and rendering the bridge unsafe
for traffic. The damages were due to following reasons:-
(i) River changed its course and flow pattern with passage of time. Maximum
discharge of the river was flowing through A1 and P1. ( Fig 8)
The pile reinforcement at A1 and P1 location are exposed due to damage of cover to
the piles
(iii) Since the flow pattern is towards left side of the bridge, there has been
extensive damage to the box return on Agartala side due to piping action. This has
led to removal of soil below the foundation of box return. Due to piping action below
box return the earth filled in one of the chamber of the box has been taken away by
the water.
(iv) Based on detailed examination of U/S and D/S it was observed that existing
structures of old bridge on U/S were disturbing the flow which were removed and
water started flowing through all span. Bridge is behaving well now).( Fig 10 &11).
Steel truss bridge with timber decking of 236 mtr length located at km 42.590 on
Dhar- Udhampur road in Jammu & Kashmir. This bridge was constructed during 1962 for
single lane requirement. The bearing of the bridge got dislocated due to traffic movement
and due to repeated seismic activity in the area has been rectified.
Salient features of the bridge are as under :-
There are 8 spans of the bridge and bridge is single lane only. Dislocation of bearing
was observed during are inspection.
Due to dislocation of rollers out of bearing plate at two bearing location, bridge
become unsafe for heavy traffic. Immediately it was decided to relocate this bridge bearings.
The wooden sleepers were placed under the cross girder on the pier cap girder near bearing
(both upstream and downstream sides) to stop further movement of rollers of bearing as a
temporary measure.
Based on this defect, a rehabilitation plan was made and on assessment of the dead
weight of the superstructure, it was decided to jack up bridge. Based on the calculation, it
was found that the dead load was approximately 45 MT and jacking up plan was made
accordingly alongwith position of jacks for application. Acton was implemented by the
trained team of technician of department and whole task of relocation of bridge bearings was
accomplished in six hours..( Fig 12,13,14& 15)
(a) Placing of wooden sleepers below girder (near bearings) to stop further
movement of bearings.
(b) Placing of 04 nos mechanical jack 50 ton lifting capacity below end of main
girder.
(c) Lifting of girder with jack and making roller position free
(f) A slopper plate was fixed to stop further moment of roller in future bridge is
now behaving well.
A Kunifer bridge located NH-1on Jammu-Srinagar road. Silent feature of bridge are
as under:-
It was observed that there is dislocation of bearing. Abutment was bulging out and
cracks in the cap beam. The cap beam was not reinforced during initial construction.
Details of defects are as under:-
(a) Abutment cap on left side crushed under the roller on U/S girder.
(b) Top plate of roller bearing of U/S girder slipped by 10 cms and roller moved
by 20 cms.
(c) Bearing is out of location and affected the load transfer mechanism.
(d) Expansion joints at both side were also not functioning due to problems in
bearing.
Fig-15 & 16 Dislocated and Jammed Bearing
Based on the distress observed and review of cracks, a detailed rehabilitation plan
was made to bring the bridge into original condition for regular traffic. Following actions
were planned for this bridge( Fig 15&16)
(b) Replacement of existing cap beam with reinforced cap beam after lifting the
superstructure.
(e) Replacement, expansion joints and approach slab on the both ends.
Rehabilitation was very cost effective
4.0 Recommendation
To ensure that bridge serve as per the designed life following recommendation are
made :-
(a) All the bridges should be constructed as per approved designed standard to
avoid any distress before completion of serviceability period.
(b) After construction, all bridges should be monitored closely on regular basis
and distress if any should be attended to avoid its aggravation.
(c) It has been observed that few bridge site have very serious distress but due
to non availability of fund it got aggravated led to major expenditure at later
date. There is need that all bridges where distress is noticed should be
attended to on priority. Financial requirement should also be managed in time
to avoid delay.
(d) There is need that manpower deployed in remote area should also have
sufficient training to handle distress to bridges as connectivity to remote area
is very important.
5.0 Conclusion
Bridge rehabilitation in remote area is big challenges for engineers but with regular
monitoring the distress even at initial stage can be arrested and bridges can serve better.
There is need that all bridges in remote area should be closely studied in advances and
team should be prepared to handle to distress if any. Infact to handle distress in bridges
there is need that team deployed at site is fully aware about the construction history of
bridges so that rehabilitation is handled in time.
REFERENCE
15. Dhiman R.K. Construction Challenges for Bridges in Hilly Area An Over
View - Indian Road Congress (IRC) Indian Highways Jan 2004.
16. Dhiman R.K. Damages to Bridges due to Flash Flood A Case Study -
Indian Road Congress (IRC) Indian Highways Oct 2004
17. Dhiman R.K.- Bouldery Bed Scour Proposed Formula Indian Road
Congress (IRC) Journal 65 Vol-3 Paper No. 508. Nov 2004
18. Special issue on Round Table Conference on Scour Around Bridge Pier
1993 Indian Institute of Bridge Engineering (IIBE), New Delhi.