Jigme Choden & Sonam Chukey
After remaining closed for over 18 months, the reconstruction of the Changjiji cantilever bridge has begun a fortnight ago.
The bridge which connects Changjiji to the Expressway was built in 2007.
The cantilever on one side of the bridge had moved and compelled the thromde to close it in June 2018 for safety of the commuters.
Thromde’s engineer Dendup Lhamo said the initial plan was to reconstruct only the side that was sagged. “Since there were cracks on the abutments, it was decided to reconstruct the whole bridge,” she said.
Why the bridge failed?
Thromde officials said that the bridge was repaired in 2016 due to bulging of abutment and parts of counterweight on the beams on the side next to the Expressway were removed. A study into the collapse of the bridge stated that this might have been for the ease of work or appears to have been removed to facilitate maintenance work. The counterweight comprises of soil and pebbles.
During an inspection last year, the inspectors found big space left where they could move around the area freely as the volume of counterweight was much less which supposedly to be compact.
The secondary beams of the cantilever had rotten. This is attributed to moisture during monsoon. Mud mortar and cross beams deteriorated from rain and resulted in cracks on the wall of the abutment.
The contractor carrying out the reconstruction, Jigme Namgyel said the new bridge will have glued laminated timber which is more durable and moisture resistant compared to the heavy timbers used then. “We’ll use concrete mortar in place of mud mortar for the abutments. The old materials are carefully inspected during dismantling and would be reused.”
Jigme Namgyel and his 18-member team of construction workers called Dash Group based in Thimphu started dismantling the bridge on December 27, 2019.
The bridge designed is changed and it would be bigger. The budget for the construction is estimated to be around Nu 9.4 million. “It could be lower if more materials from the old bridge could be reused,” said Dendup Lhamo.
The bridge was supposed to open by the academic year 2019. It was suspended because the works and human settlement ministry released the bridge design only in 2019. Other factors were budget constraints and the risk to workers from the swollen monsoon river.
The bridge is expected to open to the commuters in the six months.