I live a few miles from a bridge to nowhere. It was built a few miles from a centre of population. There was a bridge already at that place and another a few miles south. It cost $millions and is of questionable value. I’ve been over it a few times and it’s a lonely place. Usually there is not a single vehicle on it for long periods of time.
The bridge to nowhere in the news recently is a little different. There was a need for it but it had to be an engineering marvel to avoid disrupting a massive stream of traffic. It was designed to be moved suddenly into place with only a brief disruption late one night… It was a fine plan. It made the news. People loved it.
There was one dreadful weakness in the plan however. It was made of reinforced concrete. The marvellous structure was intended to be supported by a column bearing suspension cables and the reinforcements at each end were to be tied into concrete and steel at both ends. Wonderful. Marvellous. It wasn’t installed properly. Recently, a span was put into place and it was left to bake in the sun and shake with traffic moving underneath with no suspension and no tension in the reinforcing steel. That’s a crime. The engineers who planned the installation should be locked up forever for the lives they’ve taken.
Let me be more clear. Concrete is marvellous. It can be shaped smoothly, coloured brightly, made graceful in appearance, and has high compressive strength. Compression happens in the upper member of an “S” beam, which this bridge resembles, as the span sags slightly under its own weight. The crime, however, is that the lower member upon which pedestrians were to walk, is under tension as the bridge sags, not compression. To counter that, the normal procedure is to use steel rods, cables or beams in the lower member to hold everything up. The concrete keeps the steel parts in line. The steel keeps the concrete parts from coming apart. The steel still sags however and must be anchored at both ends and supported from above in this elegant long span. It wasn’t.
So, the span is resting there, shining in the sun, a thing of beauty. Heating, cooling and the rumbling of the traffic causes a crack anywhere in that span and the crack grows, just like in your windshield… Finally, a piece of concrete falls away anywhere along the span. The whole apple-cart is now upset. Steel moves out of position. More concrete crumbles under tension. The thing fails like cloth ripping. Stresses build at the weakest point until the span falls down like it did this afternoon crushing people moving underneath.
Look at the pictures of the scene. Notice the fractured concrete, not at the lower edges but at the upper edges. Under compression when the cracks grew there as the span bent further the concrete disintegrated and the last measure of rigidity exploded in fragments. Hundreds of tons falling several metres is like a horrible mouse-trap, only there were humans underneath. The only thing that saved any was that the lower parts of the bridge fell in chunks around the bending/failing points.
This is a catastrophe. It was totally unnecessary. It was preventable. Multiple people had to make multiple unsound judgments to make it happen. They need to rot in jail if not to be killed. The bridge would have worked as planned if it were made of steel only, not concrete. The bridge would have worked as planned if the reinforcements had been suspended and anchored properly. Instead, lives have been lost, useful technology will be forever linked to disaster, and the life-saving passage across a busy road will be delayed a year or more. How many more will have to die because of this crime?
UPDATE – Here’s a video of the collapse. Early on in the process, the bridge bent/broke at the first reinforcement position on the top side. It needed that suspension. It wasn’t there.