Half beam pour
Half beam pour
(OP)
I always do beam pour all at one time or monolithic but I heard some engineers do it by stages especially those who don't use ready mix. For the case where the beam is poured one half first (left side) and then next day the other half (right side). There is a separation right in the middle. Wouldn't this have the same effect as flexural crack that goes above the neutral axis all the way to the compression zone splitting the beam in half?






RE: Half beam pour
The answer to your question is yes, it has the same effect as a flexural crack but the effect is not harmful.
BA
RE: Half beam pour
RE: Half beam pour
RE: Half beam pour
I was asking this because once flexural cracks form in a fully placed beam and since concrete is fragile in tension, then what would prevent the crack from forming beyond the neutral axis even if it is in compression? Supposed you have a glass, and the neutral axis is at middle, once "flexural" cracks form below the glass, won't the crack propagate beyond the neutral axis even if the glass above is in compression?
And let's say your beam is such that the stress block in compression is in the T-beam flange. When the web flexural cracks form below, what would prevent the compression zone in the flange from being affected in the crack propagation (say hairline cracks). If this occurs, it's like having half beam pour occurring anywhere in the beam. Hasn't this happened anywhere as it's theoretically possible?
RE: Half beam pour
Flexural beam design already assumes that the beam cracks (you neglect concrete in tension anyway). So a formed construction joint a midspan is no problem. Some type of shear key or roughened surface is preferred, but the formed joint is not problem.
RE: Half beam pour
RE: Half beam pour
RE: Half beam pour
We are discussing a cold joint at or near the midspan of a beam. There are no cracks to propagate. The new concrete in the compression block simply bears against the existing. What is your concern?
BA