Engineers?
Architects?
Builder?

Whats the reason for the crack at the column points, with the props are still in place

Reinforcement?
Concrete?
Workmanship?
What?


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engineer.dipo@yahoo.com
08033186563

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ABOVE ALL, I think this structure require a physical examination and interaction with the supervising engineer so that the quality and procedure used can be know.

Thanks for your response and your attempt to understand the situation given the little information you have.

I am not in charge of the building, and i can never make a mistake like this. I'm too much for it, and yes i have good structural experience.

What happened there was that a group of structurally deficient white guys decided to to run a lintel across without taking proper construction joints into consideration.
the actually stopped the first cast of the lintel on the side of the column. then drilled in 16mm dowel bars into the column to hold the entire span in place. the span in quite long for a 230 deep beam. it would deflect upon loading.

Right now, the beams are on props that are also on the ground that has low cohesion, so there was bound to be an expected insignificant settlement. but in this case, the shrinkage and slight settlement of the props has set the failure in motion. i expect that once the lintel in de-propped, it should meet with the ground 'cus the shear at the edge would be great as the beam is not acting as a continuous beam because of the cold joints.

Please note that there is no wall directly underneath that can help. there is a window spanning column to column.

Though the concrete tests give not less than 30, it has nothing to do in this case my brother because apart from the shear, under load, the concrete beam would want to pull away from the column and as such the reinforcement should take over. but there are no significant reinforcement in place, remember i said the reinforcement were drilled in.

To solve this a prop at the middle might work, but its been instructed to be pulled down.

did you also notice that the beam above, which is meant to support the steel rafters have also been stopped at the column position. this is a treat to the beam as it would crack over time at the top were most of the moment at the support ought to be resisted by the reinforcement which cant work in composite with the concrete because of the location of the construction joint. the top reinforcement is also short. I mean these are some really mean construction people, with no regard for structural engineering principles.

CASTING PLANS
On the overall what is to be learn here is that a proper construction casting plan ought to be made on all structural elements that cannot be cast at once or is too long. the casting plan would show the volume of concrete involved, the surface area, lengths, widths, construction joints with distances to the supports, expansion joints etc. this would be assessed by a structural engineer and modified if necessary. casting plans are very important and follow certain aspects of relevant BS Codes. construction joints are always calculated to fall into points of contraflexure.

POINTS OF CONTRAFLEXURE
In a bending beam, a point is known as a point of contraflexure. it is a location at which no bending occurs. In a bending moment diagram, it is the point at which the bending moment curve intersects with the zero line. Knowing the place of the contraflexure is especially useful when designing reinforced concrete or structural steel beams. it is also useful when deciding construction joints. the same goes for slabs etc.

The lengths of reinforcement specified on structural drawings are to remain until otherwise modified by a qualified structural engineer.

I am sure a few of us are familiar with this principles.

I only brought it into this forum so that we can share a lesson or two from this with many others out there without the understanding.

I appreciate your response and it shows that you may well be the only courageous person on this forum to respond with the approach of someone fully aware of construction practice.

thanks my brother.