huangyhg

requirements for bridge deck on steep slope
i'm currently looking at a highway bridge with a longitudinal slope of as much as 14%, which is more than i--or anyone else in my office--can ever recall seeing. i think i generally have my head wrapped around it with the exception of the deck. i'm concerned that it could be difficult to construct. i'm sure that a method to pull the paving machine up the bridge can be devised. however, i'm wondering if we're going to end up with bad results because of the plastic concrete heaving slightly behind the machine when the concrete is vibrated in front of the machine, or perhaps something else i'm not thinking of.
i'm also wondering if some special finish is going to be needed to provide some extra skid resistance.
anyone ever do a bridge this steep?
i have not dealt with a bridge that steep. but, a 14% slope is considered optimum for a boat ramp. years ago, as a contractor, we constructed a large cast-in-place boat ramp with approximately that slope. in those days, screeding was longitudinal which was an advantage to keep the concrete from flowing downhill. using a "stiff" concrete mix, together with due care not to over-vibrate the concrete should be enough to give a good surface.
as for skid resistance, i believe that grooved finish would help. wet weather and winter conditions could be a very big problem, however.
i once did a bridge with an 11% slope. it was on a local road over the interstate (don't think that interstates are allowed to have such grades - trucks can't use them!!).
anyway you do need to be careful to instruct the sequence of pours to be from the low to high end.
as for bearings, you may want to bolt some angles on the downhill side of the bearings as a stop. this will depend on what type of bearing your using of course.
regards,
qshake
eng-tips forums:real solutions for real problems really quick.

thanks for the (semi-)warm and fuzzy feeling and advice.
qshake: we have laminated bearing pads, and they're detailed so that they can't "walk off".
you will have problem for bottom flange undercut at bearings if this is to be precast as precasters cast this flat.
a solution to this may bevelled plate of some sort during casting, external to the flange.
hth

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