Location of Concrete Beam / Wall Pour Joint

[nicholi]

I would like justification to determine the location of a pour joint for a concrete beam and wall. The wall is approximately 2.0 meters high supported on piles, which is designed both as a retaining wall (elevation differnce between finihsed slab and outside grading )and beam to support the contiuous warehouse building loads from above. The contractor has to heat and hoard the concrete and given the size of warehouse permiter, wants to divide the work into two / three pours. Thus, where is the pour joint and why? The reason I am asking is becase I have heard 1/4 , 1/3 and 1/2 span points. Is there some agreement?

Would this change if the builing loads where point loads directly onto the piles below? What if the point loads were offset from the pile locaitons and at some location along the span? How do you determine where the pour joint location is then?

Thanks in advance for your advice.

 

[ishvaaag]

It is generally accepted that inflection points as by statical analysis are the good points to make joints like the ones you are talking about. This is because there being no moment there you won't have tensile forces from moment to pass from one segment to the other. You can ascertain from your calculation the point, but 25 to 35% are usual stations.

Anyway there are shear forces at the interface, and all the sound meaures of keeping roughness, ande clean the joint remain valid.

Reinforcement must be designed as the beam requires (as if deep beam if deep beam) and at the joint points a supplementary revision of passing the shear in shear friction with enough development length to each side needs be made.

Of course if you have some moment at the joint, the required capacities need be spliced to both sides of the joint as well.

 

[JAE]

Most suspended beam cast-in-place concrete construction joints are placed at or near midspan to avoid excessive shear across the joint. Concerns over moments are not real valid as the compressive side....well, its in compression and the tension side is dealt with by the reinforcing.

So for spanning beams/joists etc., the joint is usually preferred in the middle third of the span.