Beam with tapered ends resting on concrete beams

[jaskamakkara]

Hi, I have a need to "hang" a steel beam from two concrete beams. The top of the steel beam is 110mm above the top of the concrete but the beam needs to be at least 330mm deep so I was thinking to taper the beam ends and sit it on top of the concrete. There is a picture attached that hopefully shows it in enough detail.

My main concern is about the moment fixity. With this type of connection is it reasonable to say the beam is pin-ended? In my mind I don't think I can since there is no bolted interface or thin end-plate that will release the moments - I am concerned that the bolts at each end will end up trying to hold the beam flange down under bending and end up picking up big tensions, with the compression part of the moment couple being the interface between the flange and the concrete at the edges of the concrete beams. This lever arm will be quite small and will result in big tensions potentially. My alternative design is a bracket fixed to the concrete beam with a shear plate, this is I think better but the client doesn't like it because it's more complicated and needs much more fabrication.

It seems like such a simple connection but I can't get over this concern I have with there being some moment directed to the beam ends, the concrete is old we don't have much information on it so I am trying to keep any anchor forces to an absolute minimum.

What do you guys think? Maybe if the bottom flange of the tapered parts is thin enough then I can assume moment releases at the ends and I can ignore any nominal tensions in the bolts?

 

[HTURKAK]

Use rubber pad under the steel beam supports to make free rotation at supports..Another alternative, the use of steel pad having limited thickness which i will not recommend..

Good luck..

 

[MIStructE_IRE]

I like the rubber pad idea too. Although I’d still like to see stiffeners at the cranks.

Alternatively change the connection.

 

[jaskamakkara]

Use rubber pad under the steel beam supports to make free rotation at supports..Another alternative, the use of steel pad having limited thickness which i will not recommend..

Good luck..

Sounds good, I also thought a neoprene pad underneath the flange would do the job.

Alternatively change the connection.

Is the idea that the angle seat (or the end plate welded to it) provides a rotational release? I would guess so since the bottom flange of the steel beam wouldn't be continuous so would it be reasonable to design the angle seat for pure shear?