AMSTERDAM, The Netherlands (Bentley Be Inspired Conference), Oct 28 2010 - Cable stayed bridges, and their many variants, seem to be all the rage, having supplanted the even more graceful suspension bridges as the bridge of choice. The reasons cited are always ease and cost of construction, as the decks of cable stayed bridges can be built out from the towers. I'm not a civil engineer so I'll take them at their word.
Cable stayed bridges make the news these days due their spanning of enormous waterways. I imagine they are not cheap. I'm now used to them popping up in well-off countries. It gave me a start to see one being built in Bangladesh. High Point Rendel has made a 950m long "extra-dosed" bridge across the Karnaphuli River.
This project was a finalist in Bentley's Be Inspired Awards, held in Amsterdam in October of 2010. It did not win.
Bangladesh is one of the poorest countries in the world. I've not been there but was close when I was in Kolkata, India, a city known for its crumbling infrastructure, much of it not updated since the British left 60 years ago. I wondered how Bangladesh got the funds to create this bridge or how they are going to maintain it.
Of particular interest to this part of the world:
- Quality of concrete was critical. This type of bridge depends upon high strength concrete that up until now may never have been made in such an impoverished country.
- Special slow lanes for the foot, rickshaw and bicycle traffic.
- Seismic load due to scouring (shifting silt in the river bed)
I paid special interest because I had set up a small office in India, which at many times along the way I considered an impossible task. That part of the world has a way of exasperating foreigners. I am simply astounded that something as ambitious as a bridge can be created. Not only did HPR succeed, but it is buoyed by the success of the bridge. They proclaimed proudly that "the days of not building high tech bridges in the 3rd World are gone." In fact, Bangladesh holds a special interest for future projects, as it is a country sliced and separated by multiple north-south waterways, almost all unbridged.
In other words, Bangladesh is a "bridge designers heaven."