And yet, here it is - the most awesome, the most beautiful bridge in the world! (Pic courtesy: samizdata.net)
The challenges were many - from pouring out concrete into the super complicated shaped pylons (an Architect's dream may be an Engineer's worst nightmare!), which required reshaping and reinstalling the multi-tonne casts every 4 m, and over 250 times in all, to figuring out how to push out the steel decks over the slim and slender pylons. Here's how they did it (from Wikipedia):
The bridge deck was constructed on land at the ends of the viaduct and rolled lengthwise from one pylon to the next, with eight temporary towers providing additional support. The movement was accomplished by a computer-controlled system of pairs of wedges under the deck; the upper and lower wedges of each pair pointing in opposite directions. These were hydraulically operated, and moved repeatedly in the following sequence:
1) The lower wedge slides under the upper wedge, raising it to the roadway above and then forcing the upper wedge still higher to lift the roadway.
2) Both wedges move forward together, advancing the roadway a short distance.
3) The lower wedge retracts from under the upper wedge, lowering the roadway and allowing the upper wedge to drop away from the roadway; the lower wedge then moves back all the way to its starting position. There is now a linear distance between the two wedges equal to the distance forward the roadway has just moved.
4) The upper wedge moves backward, placing it further back along the roadway, adjacent to the front tip of the lower wedge and ready to repeat the cycle and advance the roadway by another increment.
When I see these programs, I realise how we tend to over-glorify ourselves at the smallest achievements!
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