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London Transport (uk.transport.london) Discussion of all forms of transport in London. |
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Truck weights and bridges (was: Stating prices at retail inclusive of taxes)
In article ,
Adam H. Kerman wrote: But what about the way spans are designed to flex? There are several trigonometric formulas that apply (that I never learned). Aren't there instances in which the same live load on various wheelbases can positively or negatively impact the span's flexibility by creating different kinds of deflection? Things get complicated, and messy, in the real world. wry grin Longer distances between axles can serve to spread the load over a larger part of the spam, without increasing peak loading. Additional axles, on the same overall wheelbase, can reduce the 'rate of change' of the load at a particular point, BUT they can also _increase_ the peak load at a particular point. This can be significant, at/near the weakest point -- mid-span. 'Drive' wheels apply different forces on a span than "non-drive" wheels do. Powered axles, in addition to the 'down' force of the load, provide a 'push' towards the rear of the vehicle. Un-powered ones have the effect of adding a push towards the -front- of the vehicle. This adds increased compression effects _between_ the drive and non-drive axles, an a reduction before the drive axles, as well as after the non-drive ones. These forces aren't large, but can make for some significant changes as they pass over the mid-span 'divide'. |
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