Beam support along edge

[oranda]

How do you design a continous wide beam (between 1.2m to 1.8m) support along the edge by columns (ie. some columns are not located along the centre line of the beam)?

What I mean is that the columns don't really effect the spans of the beams, but how does the loads get transfer from the beam to the column when there are a bit of eccentricity from the centre line of the beam to the column.

Thanks

 

[dik]

Design the bracket (plate or T-section?) for the moment due to the beam eccentricity, use the plate as a web stiffener and add one outboard and design the column for the moment...

Can either bolt the 'T' to the column or have the plate on the column and bolt it through the web. Shear not likely an issue and flanges take most of the moment...

 

[JAE]

Is this concrete or steel? Sounds like concrete to me.

If it is concrete, the eccentric beam can be analyzed as a straightforward continuous beam. At each column support, you must design into the beam/column connection a bracket/corbel type of reinforcing arrangement.

Then, you must include the resulting moment that is transferred from the beam eccentricity to the column along with the axial loads.

 

[chicopee]

Eccentricity at beam to column connection means moment.To have a moment connection on steel beam, reinforcment is needed in the form of stiffners. Such stiffners are normally installed by welding plates between flanges and to the webb. Stiffners are places on both on both sides of webb at connection level. Refer to the AISC steel manual, it has great illustrations.

 

[dik]

Oranda:

It does sound like concrete... can you confirm; thanks, JAE. Just finishing up a large steel project and have it on the brain.

If concrete, then how far is the edge beam from the CL of the column? There will be a point where the the top mat over the column will create a lesser moment in the column and also will diminish the moment in the top mat... The rigidity of the beam will have a lesser effect on the 'column strip'...

 

[oranda]

Yes, it is RC or post tensioned continous beam supported on RC column (& possibly steel column as well). It is still at a conceptual stage.

Thanks for all your help.

 

[ARIFSIDDIQUI]

THE APPROACH OF JAE FOR THE DESIGN OF SUCH SYSTEM IS ABSOLUTELY PERFECT.

ARIF ALI SIDDIQUI
STRUCTURAL DESIGN ENGINEER
IMCC 8 JANTAR MANTAR MARG
NEW DELHI INDIA

 

[cyak]

While analyzing the system, in order to model the concrete continuity you would assume fixed connection of the beam and column. The eccentricity of the beam is better modeled via an elastic beam secion and not rigid offset (if the eccentricity is large).

It has been found that there are local effects in that connection so you have to reinforce so that the eccentric beam-column connection acts in the way you assumed in the analysis. Rigid fram action is hard to accomplish...