2007-01-06 17:54:26 · 5 answers · asked by GUNA S 1 in Science & Mathematics ➔ Physics
They age over time due to resonance.
2007-01-06 18:00:45 · answer #1 · answered by apollo 2 · 0⤊ 0⤋
Most materials deteriorate over time. Cement crumbles and iron rusts. They also deteriorate due to stress. A truck crossing the bridge causes more stress than a truck parked on the bridge because the pressure on the bridge is changing. Repeated bending of iron breaks it due to metal fatigure.
Methods of analyzing bridges have improved. The Tacoma Narrows bridge collapse was due to unexpected resonance from swaying in the wind. We've learned a lot about earthquake behavior of structures.
Standards are becoming tighter. We are no longer content to build a bridge to survive a 5.0 earthquake, but now demand survival of even stronger quakes.
2007-01-07 07:46:55 · answer #2 · answered by Frank N 7 · 0⤊ 0⤋
Because of they continues use and (Ton-age weight) bridges last so long be-fore they start to go out and the bolts begin to give way if that happens the bridge becomes unsafe to drive on anymore.
Look it's just like the human body say for instance if you are carrying a heavy load across the room say from (.0 ) to ( 30 feet ) and you have never carried that much weight before your arm will start to give out on you. Or if you began to put on the weight over the years and your body is not use to that then what happens is the weight of your body put stress on your hips and legs and if that happens then your body can no longer carry you and your knees start to give out from the extra body weight, it's the same thing for bridges there's no difference between the two.
I hope that answered your question...
2007-01-07 02:55:03 · answer #3 · answered by Anonymous · 0⤊ 0⤋
It has got to do with something called elastic creep. An object constructed to operate under strain continuously creeps due to the continued force acting on it. Eventually this creep causes the object to snap even if the forces acting on it are balanced.
This is why objects fall off a wall over time when put up with cellotape.
See also Young's modulus, stree, strain and hysterisis
2007-01-07 16:47:03 · answer #4 · answered by sheer_carisma 1 · 0⤊ 0⤋
they get weak after lng time due to continous pressure eg how long can u hold a 40kg dumbell in ur hand?
2007-01-07 02:02:12 · answer #5 · answered by Akshay p 2 · 0⤊ 0⤋