This is a Structural doubt on cantilever slab posted by a structural engineering intern in civilera structural community. I thought of posting this in this general civilera structural forum so that more civil engineering freshers are benefited. By following our forum and blog and actively participating in structural discussions here, you can learn tips and tricks in structures.
In this structural question, the student wants to know about the possibility and options to support a particular slab that she has come across. See the sketch and video to understand this better.
I also want you to understand that based on the situation and site conditions and the requirement, one or more or even a different solution may be workable. Also, all the designs should meet the strength, serviceability and stability requirements. So, don’t freelance structures unless you have enough experience or a mentor to guide you around with your doubts.
The solution I have provided for this question also need some better understanding of load or moment redistribution. Redistribution is nothing but the load taking an alternate load bath deviating from the normal stiffness-based path when there is a slight lack of strength in that direct primary path. Code allows certain redistribution and if you don’t know about it, please check this blog
Also, when the slab cantilever is at a different level there are chances of instability issues and the beam may be subjected to equilibrium torsion and you need to attend to it. You can read about torsion in beams here
Also, the anchorage of the slab rebars is of importance especially when it is a freestanding slab with no back anchorage. Even if you have all the necessary strength and all other considerations attended in design, if the anchorage is not correct, the slab can fail in anchorage and can create an unforeseen disaster. This failure can be more sudden than we think and hence ensure we have proper detailing of rebars incase the cantilever slab is at a different level and is freestanding as I have explained in the video.
You can also see two additional and similar blogs in our blog section. I have cross linked it below for your learning. One structural blog talks about the refurbishment of a slab. Refurbishment is nothing but strengthening or altering an existing slab or making any kind of structural modification to an existing structure. It could be even strengthening a slab for an additional load carrying capacity due to functional use change.
Another similar blog is on a few tips when you have cut outs in slabs. That blog and video is very closely related to this question and can be useful to understand all about cutouts and how to tackle it in software like etabs.
If you have more questions on this topic, please feel free to ask here and also initiate new discussions on relevant structural topics.