RC Beam-column Joint with one beam connected to the column at a different level 1

[kellez]

As the title explains I have a RC beam-column joint where one of the beams is connected to the column at a lower level than the other two beams.(see picture below)
Is there going to be any issue with the column in the event of an earthquake? Do you guys have any advice for this type of joint?
Are there any restrictions for these joints in the design codes for earthquakes

The building is a 1-storey reinforced concrete frame
I am designing according to EC2 and EC8 therefore designing for earthquakes

 

[atrizzy]

Is this column and beam system part of your lateral load resisting system?

 

[kellez]

Hi,

Yes the column is part of the lateral load resisting system however the beam (rc beam 2 shown in picture) could be designed as a secondary element since it only carries its own load.

 

[KootK]

It would seem that you've one of two primary paths from which to choose:

1) Create plastic beam hinges in both beams. In this case, you'd need to design everything from the top of the high beam to the bottom of the low beam as the "joint" and ensure that there's enough capacity there to force hinging in the beams.

2) Create a plastic beam hinge only in the upper beam. In this case, the low beam may well improve matters seismically as it would effectively stiffen/strengthen the column at the joint.

I like path #2. In the US, there are provisions specifying a tie force between the primary structure and ride along elements. I'm sure there's something similar in EU.

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.

 

[kellez]

ok lets say I dont really want the lower beam (rc beam 2 shown in picture) to be part of the lateral resisting system and i only need it to provide support of the brick wall below it. is there any other approach?

 

[kellez]

What if i designed the lower beam with hinge joints at both ends and provide the minimum possible for anchorage at both ends?

 

[KootK]

What if i designed the lower beam with hinge joints at both ends and provide the minimum possible for anchorage at both ends?

This approach doesn't make sense to me in a monolithic concrete structure. Just assume the low beam not to be part of your lateral system and design it to be able to withstand the expected drift etc. Trying to disconnect things in monolithic concrete construction for the sake of simplified analysis is usually inadvisable in my opinion. Continuity is really the power of reinforced concrete construction.

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.

 

[briancpotter]

Kootk-

I'm not sure assuming the low beam as not part of the lateral system is conservative.

The issue I see is that the low beam(s) are probably going to attract lateral force regardless of whats assumed - my guess is the heavier lateral elements of the larger, left portion of the building are going to attract load and the two low beams are going to act as collector elements to transfer it from the smaller portion of the building.

Brian C Potter, PE
Simple Supports - Back at it again with the engineering blog.

 

[KootK]

I'm not sure assuming the low beam as not part of the lateral system is conservative.

Modern concrete buildings in north america use this strategy all over. Most beams and columns in a concrete structure will be "gravity only" and thus designed simply to accommodate the drift of the designated lateral system. In that way, they are made capable of resisting whatever load they would attract. Really, this results in those members being able to resist even more load than that as the frame drift is overestimated.


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.