Project Value: 4361.4 million BDT
Client: 16 Engineers Construction Battalion (16 ECB), Bangladesh Army.
Contractor: Infratech Construction Company Ltd. and Hercules Engineering (Malaysia)
Details of Existing Meghna Bridge:
Length of Curved Bridge: 930 meters
Carriageway :9.20 m
Construction Period: 1986-1991
Location: On the 25 th km of Dhaka-Chittagong Highway
No. of Span: 13 nos.
Type of Super-Structure: Pre-stressed Box Girder
Condition of Meghna and Gumti bridge before rehabilitation:
1. The expansion joints were fully damaged and prevents free flow of traffic
2.Due to overloaded and increasing number of heavy vehicles hinge bearing performance was fully collapsed.
3. Due to high turbulence and tide water, serious scour of riverbed occurred specially on the pier no: 7,8 and 9
Rehabilitation Measures taken for Meghna and Gumti bridge:
To protect the bridge government of Bangladesh took a project named ‘ Meghna and Gumti Bridge Rehabilitation Project’ and was implemented by 16 Engineers Construction Battalion , Bangladesh Army.
Rehabilitation completed in Three Steps:
- 1st Step of Rehabilitation-Replacing the Expansion Joints of Meghna and Gumti Bridge:
On the first step, a detailed preventive measures were worked out on expansion joints and its performance. The bridge was remain closed for 7 consecutive nights. At first temporary measuring steps were carried out such as fastening the expansion joints plate,anchoring the plate, welding etc.
At the second step, the existing expansion joints were replaced by Finger type joints. To do this a high early strength concrete mix design were prepared and the bridge was closed for 18 consecutive days in 3 phase. in each phase 6-14 nos. of expansion joints were removed and replaced with finger type joints.
To remove the existing joint Hilti 1500AVR hammering machine was used. Before applying concrete, to make proper bonding of old concrete and new concrete Nito Bond chemical was applied on the previous concrete surfaces. To have a good initial strength of concrete Glenium Ace 30 JP was used as admixture. After concrete when the concrete surface hardens then for proper curing MasterKure was applied over the newly placed concrete surface. Intensive care in curing done by applying water for 10 days continuously.
- 2nd Step of Rehabilitation-Replacing the Hinge Bearings Meghna and Gumti Bridge
The hinge bearing of Meghna and Gumti bridge was fully collapsed and was created a huge sound when vehicle passes by before replacing. The replacing of expansion joints and hinge bearing was carried out at the same time. The newly placed hinge bearing was prepared in Malaysia and tested for abrasion. It has a 5 mm thick brass plate over its main surface. After replacing the existing one, after some days it has been noticed that, the top of the bearings are polished due to high abrasion factor. Then it was suggested to use non abrsive brass over the surface. After replacing the hinge bearing with the abrasion resistant brass hinge bearing the problem gone out and the hinge bearing was completely OK again.
- 3rd step of rehabilitation- scour Protection on Meghna Bridge
This scour protection is done on only Meghna Bridge around pier no: 7,8 and 9. Gumti bridge has already been silted and there is very less probability of scouring.But, Meghna is a tidal river with heavy current. That’s why, the bed level around pier no. 7,8 and 9 was gone to -21 m in some portion that indicates that there is heavy scouring.
To solve the problem at first the scoured bed is filled with sand filled gunny bag. Around 64 bag gunny bag were dumped into the river with around 80 kg of sand containing each sack.
After completing the filling of bed surface, geo-textile bag containg around 5 cft of local sand with FM greater than 0.8 dumped on to the elevated bed level. Around 2.1 million geo-textile bag filed and dumped.
After that to protect the bridge pier from further scouring around it, 72000 thousand of 600 mm x 600 mm x 600 mm concrete blocks were dumped around bridge pier.
After that to seal the pier head that was exposed to the environment due to scouring , concrete mix has been pushed under the bridge pier head.
And that’s it.The works done.