I started to do some rough sizing of the box girder and columns/piers. The Leonhardt steel box girder section that Dong posted yesterday is suitable for spans of about 25m, so I suggest we start with that. We can use a steel box girder for spans up to 60m, but it would get deeper.
The most slender 4-meter-tall column that complies with the American Institute of Steel Construction is 5-inch (0.13 m) diameter. We would need one column for about every six meters of span. In other words, if we had a 36-meter-long span, we would could support it with six columns (three at either end). Each of our bridges will be about 150 meters long, so they will require about 25 columns each. We have quite a bit of leeway to scatter them where we want.
The span can slope up to 1 in 20 to avoid landings. The box can bend in plan to a minimum inside radius of 5.5m (this is super tight and I assume we won't bend this sharp).
6 comments:
ps- I will try to get my hands on Eurocode and see how slender that will let us go with the columns.
scott you are ruling. this is way rad.
about the box girder, the column isnt centered. is this intentional? do you have guidelines for the amount of leeway we have to offcenter the columns?
also, would it be possible to have multiple box girders, say two or three lines, kind of like metal decking? just curious. it would allow us to place columns in multiple places along the width of the bridge and might also think the depth of the girder(s). maybe. i think i saw an section like this in the leonhardt book. ill post it if i can find it.
Yeah, it is fine to put the columns off-center as long as they connect to the bottom of the box and not to the cantilevered top plate.
It is common to use two smaller box girders, instead of one larger one. However, this would reduce the torsional strength and stiffness (i.e. not as good for curving the bridge in plan).
We can make the single box girder the full width. We just need to make sure that it can be welded up from the outside! (box girders for highway bridges are large enough for guys to walk around inside and weld.)
Yeah, post up any other cross-sections you see and like. I will do likewise.
I found Eurocode information in "Steel Building Design: Design Data" by Corus ( http://www.corusconstruction.com/en/design_guidance/structural_design/eurocodes/ )
Eurocode allows columns even smaller than the 5 inches (0.13 m) allowed here in the states. I am going to look at this closer, but it seems we theoretically would be allowed to use columns as small as 0.033m diameter!
.033 diameter is what eurocode allows or what we structurally could go down to? would we need more than 25 columns per side? siiiiiick.
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