Another concrete corbel question
Another concrete corbel question
(OP)
Hi everyone,
An Existing corbel is to support a new precast beam. The corbel doesn't have the capacity to resist the reaction from the beam. Can we provide plates like the ones shown in the attached sketch welded to existing embedded plates in the column to reduce the load applied on the corbel? We thought we can do load distribution between the corbel and the new plates based on relative stiffness. How?
1- Apply a unit load on the corbel and the plate and calculate deflections due to bending, compression, and shear,
2- the load carried by the corbel/the load by plate = deflection in plate/deflection in corbel.
Is this correct?
If yes, what do you think can go wrong? BTW, we know that carrying all the load on the corbel is more certain approach, but the corbel, that is one of many, need be demolished and re-built, which we don't mind doing if other ways are not available.
An Existing corbel is to support a new precast beam. The corbel doesn't have the capacity to resist the reaction from the beam. Can we provide plates like the ones shown in the attached sketch welded to existing embedded plates in the column to reduce the load applied on the corbel? We thought we can do load distribution between the corbel and the new plates based on relative stiffness. How?
1- Apply a unit load on the corbel and the plate and calculate deflections due to bending, compression, and shear,
2- the load carried by the corbel/the load by plate = deflection in plate/deflection in corbel.
Is this correct?
If yes, what do you think can go wrong? BTW, we know that carrying all the load on the corbel is more certain approach, but the corbel, that is one of many, need be demolished and re-built, which we don't mind doing if other ways are not available.






RE: Another concrete corbel question
RE: Another concrete corbel question
The corbel is infinitely stiffer than the angles you show an will fail before any significant load gets taken by the angles (it already is taking all the existing load).
How are the existing corbels failing?
RE: Another concrete corbel question
The corbels are not failing. They are built now. The beams are not istalled yet but they have higher loads now than what the corbels were designed for.
RE: Another concrete corbel question
RE: Another concrete corbel question
RE: Another concrete corbel question
We were hoping the plates can do it because this is much faster way. In our relative stiffness analysis, we assumed a cracked concrete section and full fixity for the plates, which is why we have uncertainty in this solution. The result of this analysis showed about 65% load to be carried by the corbel and 35% by the two plates, which would be adequate.
haynewp,
We were to carry only vertical shear on the new plates. We're allowing for horizontal movements by providing slotted connections.
Any ideas are welcomed.
RE: Another concrete corbel question
One positive thing is your detail tends to diminish the lateral load on the corbel. Good luck.
RE: Another concrete corbel question
If "most of the vertical load" is more than what the corbel can safely support, it may then experience damage, distress or failure. This distress would mean the corbel, to some extent, moves or shifts such that the load is quickly transferred to the plates, which cannot take the vertical load all that well based on your sketch.
It all doesn't look like a good solution to me.
A better solution would be to strengthen the corbel directly. Possibly by constructing a support corbel beneath it.
RE: Another concrete corbel question
RE: Another concrete corbel question
The precast beam, when loaded, tends to rotate upward. The rotation is restrained by the plates with a couple in them. Watch out for the extra pulling/pushing forces - are both the column and the precast beam are capable to resist the forces without doubt.
RE: Another concrete corbel question
RE: Another concrete corbel question
I dont mean how is it literally failing, I mean, how are the numbers saying the corbel is going to fail - i.e. what is the critical design criteria. Is it reinforcement or is it concrete strength.
If it is failing due to insufficient reinforcemet then you can provide additional external reinforcement by way of 2 angles and a bolt each side wrapping around the column.
If it is failing due to concrete strength then you may be able to get insitu testing to justify a higher strength.
RE: Another concrete corbel question
If thus, I reserve my doubts on effectiveness of this connection scheme.
RE: Another concrete corbel question
RE: Another concrete corbel question
both steel and concrete are failing.
ksledd1000 and JAE,
So you don't see this connection to work?
RE: Another concrete corbel question
So...no, it doesn't look right to me.
RE: Another concrete corbel question
RE: Another concrete corbel question
Think twice.
RE: Another concrete corbel question
One possibe suggestion that no-one has thought of - remove the load from the corbel entirely by removing the masticord pad, and provide a bracket that can take the entire load.
RE: Another concrete corbel question
RE: Another concrete corbel question
RE: Another concrete corbel question
Yes,form under the corbel and allow for an opening with a foot or so of concrete head and use high slump concrete (8" say), then breack the additional concrete after few hours from casting.
RE: Another concrete corbel question
RE: Another concrete corbel question
RE: Another concrete corbel question
looks like the design part is well set. Keep an eye on construction. Good luck.
RE: Another concrete corbel question
RE: Another concrete corbel question
Also, I believe that through bolts with bearing plates front and back are better than epoxy anchored ties.
BA
RE: Another concrete corbel question
RE: Another concrete corbel question
BA
RE: Another concrete corbel question
It would be the best way among all.