Tie Rod Connection at Crown of Adjacent Box Beams

[jdilla87]

Hello all,

I am designing an adjacent box beam bridge and am wondering what would be a good way to connect the transverse tie rods at the crown of the road, which slopes 2% in each direction. As this is a wide bridge (100' roadway) we cannot just slope the deck on top of level beams because the added dead load is too great. There is also no skew so stepping the tie beam as is done is skewed bridges is not allowable. We have an example done by another company that just shows the tie rod bent at the crown and wedge plates between the beams. Is this the best way to connect the beams? Thanks

 

[MichSt]

Here’s how Ohio DOT handles your situation, see sheet 2/4:

http://www.dot.state.oh.us/se/standard/english/revisions/07-19-02 mailing/pdf/2002cms/psbd193.pdf

You can see the tie rods only extend through 2 or 3 beams and then overlap with another tie rod. This is done even when there is no skew. Using this arrangement the hole in the box beam is made large enough to make up for the change in cross slope at the crown.

Another thing you could do is call a local precaster. They are usually very helpful and will probably be able to answer your question better than we could here.

Also, why is stepping the tie rods not allowable when you don’t have a skew??

 

[TTK]

The OhioDOT detail would seem to work for Tie Rods or PT strands but seems like a hassle for normal width bridges.

All of the designs I have done have used 7-wire strand for the transverse PT and the strand simply follows the crown of the roadway across the bridge.

That is a very wide bridge for butted box beams. If you have not done so already, I would recommend that you review the PCI Bridge Design Manual for the section on transverse PT design of butted beams for wide bridges.

 

[MichSt]

@TTK - The ODOT tie rod method is actually not that bad for normal width bridges using tie rods. I have see a few 40’ or so wide adjacent box beam bridges erected in Ohio using this method. The rods are installed by the laborers while the crane is picking the next box. I could see though how this method would be a hassle if using transverse PT.

In Michigan we use transverse PT and let the strands follow the crown as you noted.

 

[bridgebuster]

The ODOT detail seems very awkward with respect to installing the boxes.

 

[Qshake]

Cumbersome or not, that is the same detail used by a lot of State DOT for low volume bridges.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[GoDucks]

The Ohio detail is very similiar to the Oregon DOT method