Construction Joint of vehicular ramp of car parking 3

[foxview11]

To all experienced construction engineers,

Our contractor wants to place the construction joint of ramp beam at the face of column support due to work difficulty if it is done monolithically. Is it safe to place the joint at the face of support? What provisions to be made if such joint is placed at the face of support? Please give your opinion on this issue. Thank you.

 

[CELinOttawa]

Sketch, please.

 

[foxview11]

Thanks celeinOttawa,

Attached is the plan of ramp beam

 

[PSEPK]

IMHO, should not be a problem, provided ramp beam size and reinforcement is revised as per new situation.

 

[CELinOttawa]

Thi is a natural place to have a cold joint... I would have designed to accommodate one here.

Definitely something you can allow; Just make sure they use proper detailing with a key and steel accross the joint, ideally plus a roughened surface, or (alternatively) design and detail for an expansion joint.

Personally I would never put an expansion joint at a change in grade or slope, unless absolutely unavoidable.

 

[foxview11]

Thank you CelinOttawa & PSEPK, your opinion is highly appreciated.

 

[hokie66]

In general, construction joints in beams at face of supports should be avoided. However, in this case it does make some sense. But I would want the beam to bear at least 50 mm onto the column, preferably more.

 

[KootK]

How does one go about coupling the beam bars into the columns in a situation like this? I would think that coming out of the column faces pitched and radiused would make form saver style couplers difficult.

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.

 

[CELinOttawa]

Could use:

- Small bars to be site bent (pain in the butt, but very simple)
- Spiral stirrup & links
- Drossbach ducts
- Threadbare & Couplers
- Elephant foot ferrules
- Embedded steel beam & joint
- Weld plates

 

[ajk1]

A really bad place to put a construction joint but if it absolutely has to go there, then you must carry out the design to accommodate it, which means in my opinion that you have to transfer the shear across the joint by shear-friction. So carry out the shear friction calculation. You may have to increase the amount of steel crossing the joint to provide enough shear friction resistance.

Can they not stop the column at the transverse ramp beam soffit and run the beam over the top of the column, then continue the column on up? Is that not the way it is usually done at transverse ramp beams? Seems much better than placing a joint at the column face.

 

[KootK]

Thanks for the suggestions CEL. I'll do some research and check 'em out.

I'm with AJK here in that I think that shear friction is a high priority. And that means top steel properly anchored within the columns to develop fy and to transfer tension back down to the beam compression zone. Hence my concern above regarding constructibility of the joint.

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.

 

[hokie66]

Shear friction...bah! But then you knew I would say that. How would you have done it before shear friction was invented? Bearing.

 

[neznajko]

Although I haven't always followed this ACI states:

...6.4.4 — Construction joints in floors shall be located
within the middle third of spans of slabs, beams, and
girders.
....

 

[KootK]

Agreed on all counts Hokie. I'll always take bearing in addition to FS when it's feasible.

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.

 

[foxview11]

AJK,et al

The idea of AJK is good, but ramp beam will land at the floor deck connecting the ramp. what we are going to do,
is put extra bars across the joint on both sides extending to the mid span of the beams adjacent to the column.

 

[ahmedhegazi]

I would do the following, if the joint can not be in middle third of the span

1- Check shear friction and get reinforcement required ,this reinforcement is not added to what required for bending , you should use the bigger

2- Before second poor is cast , make sure surface is rough to Amplitude 5 mm and old concrete surface is free debris and wet the surface (hydrate the concrete

3- Some contractors use bonding agent (which i do not believe is much useful)

 

[CELinOttawa]

3- Some contractors use bonding agent (which i do not believe is much useful)

I will see your "not useful" and raise you a "dangerous bond breaker when applied incorrectly".

Surface Saturated Dry (SSD) remains the gold standard for good reason...