Transfer beam modelling analysis and design

[Peter_L]

I have a building where a transfer beam is required at a lower level to allow for the removal of some columns for vehicular access.
My first attempt is a single span beam over two bays but my problem in modelling is to cope with the end moments which arise in the columns as the columns won't be able to large moments?
I can reduce the column stiffnesses to shed some of the moment back to the beam or design the beam for the full simply supported moment but not sure what the correct response is?

 

[rowingengineer]

Genrally it is best to try and get a back span for the transfer beam.

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[Peter_L]

Thanks I am looking at doing that on the internal side but can't on the outside of the building. I can try and make the columns as slender as possible about the in-plane axis and use a cracked stiffness but still concerned about the level of moment the model indicates will be transferred to the column

 

[KootK]

- stiffen the beam if possible to drew moment from the column to the beam.

- capacity design a a flexural hinge into the top of the column and design the column for the associated hinge moment.

- post tension the beam.

Frankly, if you're having this problem, I take it as evidence of your transfer beam not being stiff enough. Attempting to fix that by softening and potentially weakening your column seems sketchy to me.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Peter_L]

More stiffness equates to greater depth and hence comprises on floor height. Prestressing is a definite option which I am looking at but then requires a different level of construction expertise for an isolated activity and is not something that many local building contractors are familiar with.

 

[KootK]

Another strategy that can be employed in multi story buildings is to have partial transfer beams at multiple levels, distributing the "transfer" over several stories. Disadvantages include:

1) you have to be much more careful in considering the sequential nature of the construction and;

2) this might just spread the floor height problem over multiple floors. That said, extra floor height above grade is usually cheaper than extra floor height below grade. It can work well if the lower floors of the building already have high ceilings for mixed use occupancies and the beams can fit within the plenum space.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Peter_L]

The building in question only has two floors above the transfer level but carries very heavy stacking loads (16 kPa LL). Currently trying to get some more depth from the architect as first prize