The Importance of Punching Shear at the Surfside Collapse

For the more technically advanced viewers. The contribution of the steel to punching shear in this building is not as significant as the concrete's contribution. Codes around the world limit most of our punching shear formulas to JUST the concrete. Shearhead reinforcement is only used if the math doesn't work for the concrete alone and this type of reinforcement must be specially designed. This is built into the codes more as a precaution than because of any idea that the steel does not contribute at all. The reason for this is because concrete failing in shear is sudden and catastrophic and should be used as the limiting factor. Therefore In this video, we look at losing the steel reinforcement, which may be argued as insignificant, but nonetheless relevant, AND the loss of the top layer of concrete due to delamination, which would reduce punch-through resistance by as much as 25%. For more information, I recommend reading the ACI commentary on 2-way slab shear from ACI's historical records. Thanks for watching!

If all of the teachers in the world had this personality nobody would quit school. I could see a lot of younger people wanting to become engineers / architects thanks to this channel.

I took a full suite of undergraduate structural engineering coursework at a university highly ranked for their civil engineering program. Mr. Josh Porter outshines every professor and instructor I had, particularly in the ability to explain basic concepts of reinforced concrete design. He’s living up to the name of his channel. We need more like him.

Anyone else miss this guy after a few days?

I'm a structural concrete repair and strengthening contractor, and I can't count how many structures I have submitted proposals on that have not been repaired. They are sitting there with corroding reinforcing steel. $100m building that does not have the budget for a $100k concrete repair scope that is exponentially growing as it sits unrepaired.

The more I watch this series, the more I understand why you have been an expert witness in 30 cases. You excel at communicating technical information in a way that a non-technical audience can understand. Thank you so much for sharing your valuable time and energy and experience with the internet. I have learned so much watching these videos, and I am really looking forward to the next two videos that you mentioned at the end.

Love this guy and his articulate information. Very professional

I've never had the slightest interest in structural engineering, but I am finding this stuff fascinating. Thanks!

My father was a professor of Civil Engineering, specializing in structures, so I am familiar with all of this. The first thing that struck me when I saw the photos of the pool deck was how clean the tops of the columns were. There's nothing of the slab on top. I think you've identified the root cause of the failure.

Did a shot for everytime you said rebar, now I'm Spalling over.

How the hell do you manage to make this topic so interesting to me?! Hahaha I'm a veterinarian, so this is completely out of anything I've ever learned and I feel like I actually understand what you're talking about and can follow it and find it fascinating. Thanks! My heart goes out to everyone affected by this condo collapse ❤

A former employee that worked at the towers when they were newly contracted said both buildings had leaking basement ceilings from the very beginning. Residents complaining about the damage to the paint on their cars from the calcium/minerals dripping onto them. So both North and South towers had water leakage from day one.

Incredible presentation! Astounding research and analysis! Your study tops all other YouTube coverage and estimations...

Mr Josh you are a gifted teacher and we are lucky to have your insights.

My first job back in the mid 1980s was in civil engineering construction. It was there I learned that concrete is not waterproof. One of the many tasks I had was to paint the inner face of a concrete retaining wall with bitumen. No one explained why, though I was aware of steel reinforcing rusting and causing the concrete to burst. Now I know just how important it is. If only we had videos like this back then.

How is it that I know nothing about architecture, but I watch Josh's videos with absolute absorption? The half hour goes by like it was 5 minutes each time. What a talent you have for teaching, every one of these videos have been fascinating. It's a horrible, tragic subject but it's been very helpful to see the reason why this happened. Thank you so much for doing these, Josh! You are an amazing speaker!

Best YouTube coverage of this issue, by far. Thanks!

This is one of a handful of channels where I can give a video thumbs up after just two seconds, because I know it will be good! I am an electrical engineer, but you got me interested in structural engineering. Thank you! Never stop learning, folks.

Josh, thanks for keeping these vids free of conjecture, drama and creepy background music. It's refreshing to have an actual engineer explain structural engineering to the lay person in a simpler fashion. I wish more videos followed your formula. Thanks for all that you've provided.

I love that you're continuing this series. It feels like the public (especially outside of Surfside area) lose interest rather quickly, or maybe just the news loses interest rather fast. I love all these concepts as building blocks to fully see why the structure failed as it did.