Kicker Beam Design

[MichSt]

The bridge I’m working on has a radius on the off end to allow traffic to turn off the bridge. A kicker beam will be used at the end of the bridge to carry the additional deck required for the radius. The main fascia girder the kicker will frame into is a two span continuous steel girder and the kicker will frame in at about the 1/4 point of the fascia girder.

My question is does any one know of any references or have any advice for determining the distribution of the LL to the kicker beam and main girder (or any general references for this situation)?

Also, any thoughts on the design of the connection between the kicker and fascia girder would be appreciated. This will most likely be a simple shear connection. I’m not sure how thermal movements and other longitudinal force will play into the connection design. The abutment end of the kicker will be an expansion bearing.

Thanks in advance for sharing your thoughts.

 

[curvbridger]

I don't believe you will find any canned answers to this situation.

I would start with trying several load distribution methods.
Lever-rule will probably be the thing to use.

I would use one distribution factor for moment, and another for shear, and apply them throughout. Take the layout at kicker midspan or 1/3 pt to determine mom dist fact, and the layout at the abutment for shear.

When you have your design, apply some common sense checks:

1.) Don't use a weaker main girder than you would have if the kicker/flare wasn't there.
2.) look at matching the kicker depth to the girder depth. Deflections are your enemy, especially during the placement of the deck.
3.) Design your connection to the main girder conservatively. You might want to apply bolted-splice thinking and design as a minimum for 75% of the kicker's shear capacity.
4.) Make sure you can assemble the kicker connection. watch out for lack of access in the narrow corner of the connection.
5.) Remember that thermal movements at the abutment will be (most likely) not along the line of the kicker. Expansion joints are difficult here.

Good luck!

cb

 

[Qshake]

If you're using a integral endbent and the amount of flare is relatively small - the load will be absorbed into the slab and onto the beam and diaphragm thereby eliminating a need for a short cantilever.

If not then the best reference for the design of the connection is the Structural Steel Designer's Handbook which has a similar cantilever bracket connection design. It does not go into live load distribution though. The design is still remarkably simple - matter of shear and prying from the moment. You can find this type of design in other steel texts. Admittedly many cantilever brackets are much larger than their building counterparts!

The live load should be, in my opinion, treated the way we design slab overhangs. Place the wheel load on the cantilever 1' away from the curb and assume full distribution to the cantilever but that all other wheel loads are otherwise distributed. This would hold true if the flared end is small enough only to see one wheel load at a time.

Regards,
Qshake

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