Concrete simple beams 3

[Gus14]

Recently, I was consulted on structural plans, where all concrete beams where designed as simple beams where top reinforcement ended at the support and did not continue over the support into the adjacent span. In theory, although the structure will not fail, if beams where designed as simply supported, cracks over the support are expected due to the negative moment resulting from continuity of the concrete during construction.
However, my questions are;
1) What does ACI think about this ? is it allowed ?
2) How would the structure behave under a seismic action ? ( with references )
3) Could the court expert committee regard this as unsafe and sentence a substitution ?

 

[dik]

It may crack... I like continuity of reinforcing over supports... strength wise, it may not be necessary.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[MIStructE_IRE]

I’ve designed plenty of simple RC beams but always provide the minimum area of steel required over the supports. There is a detailing minimum which is normally about 50% As in my part of the world.

It may crack and simply redistribute the load as required. As long as its designed as simple and you have sufficient tension steel in the bottom then it can’t go anywhere. EDIT - i say this provided you have As min required (50% As or so) over top of support.

As for seismic, I’m not a seismic guy but I’d be surprised if there’s not a minimum As required to meet the code?

 

[rapt]

Most design codes do not allow it, even without seismic requirements. 100% redistribution is never allowed.

You will not achieve reasonable crack control over the support with just minimum reinforcement. You will need the amount you needed for ultimate strength anyway to get crack control over the support.

I hate the idea that the bottom reinforcement is expected to provide your shear connection.

Why would you do it anyway?

 

[Gus14]

Thank you, everyone, for replying, here is what I found after doing my research and the general ideas that I will say in my report ( Correct me if you think I am wrong ) :
Although the structure won't fail as it complies with the basic engineering principles, the following issues needs to be mentioned regarding non-compliance with the ACI building specifications requirements :
1) This method of analysis and design does not follow the ACI moment redistribution guidelines.
2) The design engineer used high ratios of top reinforcement, which increased the construction cost to limit the crack width, and still, he did not provide any calculations on the estimated crack widths over the support and whether they affect the assumed structure lifetime or not.
3) The details do not comply with ACI recommended details for non-permiter beams.
4) The details do not provide the structure with enough structural integrity, meaning that beams failure will be localized, which decreases the structure lifetime.

Sidenote, I don't think this is enough to get a substitution with the entire project cost, but I sincerely feel that the client had an unfair treatment. Also, there is a transfer girder that was not designed according to the strut and tie method, with no anchorage details whatsoever. So I think this will be enough for the engineer to be held accountable.