Streety McCarface
Senior Member
Weight distribution can be argued for roads because the force is evenly distributed throughout the ground, but that can't really be argued in this scenario. I don't know the structural makeup of Castle Frank station, but I'm going to assume it's a simple structure of a plate supported by beams and columns in the tunnel. Plates are inherently complex structures and the bending moments within them are far more difficult to calculate, so for the sake of argument, we'll remove a dimension and pretend the plate is a beam, and the support beams are just classic pin connections. In this case, a distributed load is still going to induce numerous bending moments throughout the structure, and these moments can exceed the design of the original structure. A free body diagram would look something like this (I made point B simply supported to show the Bending Moment Diagram):I don't think I have seen that reported.
I'm not quite sure I fully believe it either, given a 30-metre Flexity weights about 48 tonnes - about 8 tonnes per axle compared to a 12-metre bus which weighs 19 tonnes, or 9.5 tonnes per axle.
Is there signage that stops 3 buses at Castle Frank following each other - because that would be a higher loading?
This may be the loading for the streetcar, notice how the moment can increase to 89 kN*m, compare this to an articulated bus:
Which would see a bending moment about half that of a streetcar.
Let me just clarify, this is not at all how the structural mechanics of the actual station would behave, but the point is to show the significance of bending moments. Even just the increased shear stress could force the concrete to break.
The major takeaway from this is that you have to be careful with not just the force the wheel exerts on the ground, but the location with respect to the beam supports. Streetcars have very closely spaced wheels, so having two sets close together will ultimately impact the loading of the plate it is on. You can pretty much treat it like a point load with double the mass.
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