Haunch and Beam Seat Elevations for Prestressed Bulb T

[PAK_ENG]

Hi all. I am trying to calculate haunch and beam seat elevations for a 2 span bridge composed of prestressed bulb T beams. The roadway is on a crest curve.

Now for a straight gradient, it should be calculated as follows, correct?

Net camber = the upward camber due to prestress force - deflection due to self weight of beam - deflection due to deck/haunch/SIP forms.

Minimum haunch at supports = Net camber + minimum haunch/tolerance required by DOT (in my case this minimum is 3").

And therefore:

my beam seat elevations = Elevation of finished grade - deck depth - beam depth - min. haunch at supports calculated above - bearing/pad height.

Now I am a little confused in regards to a crest curve. How should I calculate the minimum haunch in this case? Using the method for a straight gradient above, I was getting quite a large haunch of over 7" at midspan, so I know I need to adjust for the vertical curve.

Should I calculate the difference between the horizontal reference line drawn from beam end to beam end and the max. height of the vertical curve along the beam = "vertical ordinate"

and then minimum haunch at supports = net camber + 3" (min. required) - vertical ordinate

or do I have this wrong? Also, what about deflection due to superimposed dead load? Should this also be subtracted to get my net camber? Some help on this would be appreciated. Thank you!

 

[3Fan]

Our DOT provides some good guidance in their BDM on determining topping thickness at any point along the length of a prestressed beam. Attached is that section.

 

[MIKE_311]

CDOT has a good example:

https://www.codot.gov/library/bridge/bridge-manuals/design_manual/example_7_2019_01.pdf

 

[PAK_ENG]

Thank you both for the help!