Did you notice the lovely cantilevered bridge across the Mo in my last post?
Punakha Dzong on the Mo Chhu
The original cantilever bridge (bazam) over the Mo Chhu was destroyed by a GLOF in 1958, which also widened the channel to be spanned from about 105 feet to 165 feet. It was replaced by a steel cable bridge, presumably with more character than these two nearby bridges across the Pho.
Steel Cable Pedestrian Bridge over the Pho Chhu
Steel Cable Bridge near Punakha
But, obviously, any steel bridge would not have been in keeping with the 350-year-old wood and stucco dzong. The problem was the new channel width. No one knew how to span such a wide channel with a wooden cantilevered bridge. In 2000 Pro Bhutan–Germany, an organization which had planned, financed, and built Punakha’s hospital and medical training facility, was asked by the prime minister to build a new wooden, cantilevered bridge. It, in turn, solicited the help of Walt + Galmarini AG, a Swiss engineering firm that specializes in bridge building.
The Bazam to Punakha Dzong
The result is a spectacular bridge that uses hidden steel elements “to stabilise the high bridge arch and to prevent it from twisting or falling sideward.” The new bridge was completed in May, 2008. At 55m, it is the longest unsupported span in the traditional cantilever architecture in the world. Be sure to follow the link above to see construction photos.
The Bazam over the Mo Chhu
Also note the location of the dredges in the above photo viz a viz their location in my last post. The above photo was taken Sunday morning when the yellow dredge was stuck.