I just saw an article about an allegedly "wonderful" pedestrian/ bicycle bridge designed by architects. It was awful. So I, snarling with rage, designed this very different one:

It's kind of like London's Tower Bridge's middle, but with a roadway outward from each side of the center towers and span. It has a raised center section that is a permanent elevated walkway. The technical term is a two-leaf bascule, but the road is also divided between the lanes so widely that the bridge towers are in the "median". There are fixed bridges with the supports between the lanes. but no drawbridges that I found.

The arch of the bridge is part of the support for the raising mechanism, and is not a true arch, rather it has three straight segments. At each end is a partly-sloped "upright" section, which serves as a stair for pedestrians. Across the top is a flat walkway.

The ground-level roadway is built in two straight lanes, one on each side of the arch, parallel to it. Each lane is broken in the middle of the channel, and each half of the drawbridge pivots at ground level at the edge of the riverbank. For each half of the bridge, the two lanes are tied together under the arch by a girder between them.

The drawbridge's lifting mechanism pulls up on the girder that connects the two lanes, and is anchored where the arch's upright section meets the flat top of the arch. When the bridge is drawn up, the girder is up in the corner of that intersection, and the ends of the roadway are sloping up above the permanent pedestrian walkway, one on each side, roughly parallel to the stairways at each end.

The raising mechanism is either a cable on a winch, or a set of two- part linkages, powered by hydraulics. Counterweights are as needed, as on any bascule.

The towers on each end can be built vertical on the river side, with the other side sloped for stairs, and braced upstream and down by additional sets of stairs, with a flat section over the roadways. The road lanes can be used by pedestrians while lowered, while the arch walkway ensures that they can always cross (those on wheels will have to wait, unless elevators are put in the towers).
-- baconbrain, Sep 09 2014

Tower Bridge' s middle section http://www.feverpr....WER-BRIDGE-02-2.jpg
except with a drawbridge on each buttress, and different proportions. [baconbrain, Sep 09 2014]

Please link the article. If you are using it as a referent, we need to see it.
-- Vernon, Sep 09 2014


Tower Bridge is my referent. That's why I mentioned it.

The bridge in the article was just so bad that I made something quite different. That's why I didn't link it.

If you mean you want to see an existing pedestrian drawbridge, well, they come in all sorts.
-- baconbrain, Sep 09 2014



random, halfbakery