Crazy cantilevered steel deck 7

[DoubleStud]

I found this video on youtube. What do you think of this deck? The guy went to the end of the deck and jumped a little bit, you can clearly see the deck moves up and down. At minute 3:55 he shows the structural detail.

 

[Brian Malone]

Very interesting analysis by all! The deck and house design by Steven Baczek looks bold and it will be interesting to see the finished structure. Mr Baczek seems to be confident and not a blowhard. His "150 pound" comments are certainly made in jest. His talk about the design appears to be rather detailed and he seems to be very engaged in the details way beyond of how the structure looks. Since I am not a structural engineer and have not personal building experience I don't have an understanding of why many have said this design obviously had no engineering oversight. Is it because the structure is fully dependent on the 4 anchors resisting rotation or the potential for bounciness or what? If the load on the four anchors and support members are not exceeding safe limits couldn't this design have engineering sign off by an engineer that has a different level of design factors? I get the comments about putting a hot tub on the deck but not everybody would consider putting a hot tub on the deck; a small table and two chairs works well for many. Should every deck be designed explicitly for a hot tub install?

 

[JAE]

I was mentioning that some type of ethical/professional response was called for not because there was no engineer involved (reportedly) and not because I don't trust architects (my son is one of "them") but solely based on the statements above that the numbers didn't work out for steel design and my own concern over longer term weathering degradation in the concrete/anchor area.

 

[Brian Malone]

I am not a PE so I don't know what potential professional censure could occur, so I am missing why any of you who see a grave failing in the design do not personally contact Mr. Baczek and point out your observation(s). The Citicorp building errors were pointed out to the design team and the outcome was a win/win. I see some passive/aggressive suggestions of sending an anonymous message. If there is an obvious concern why must a message be sent anonymously? I ask this as openly as my username is my name.

 

[Eng16080]

I don't have an understanding of why many have said this design obviously had no engineering oversight. Is it because the structure is fully dependent on the 4 anchors resisting rotation or the potential for bounciness or what?

I didn't run any calculations on the anchor bolts, but others here have, and some of them feel they're inadequate. I think that's the reason for this general sentiment. I wouldn't say the design obviously had no engineering oversight, although I think it's possible.

For me, the concern is more in terms of long term maintenance. I can see the concrete and anchor bolts potentially degrading over time, and if the deck is loaded more than it normally is in say 20 or 30 years and it has degraded, there's the potential for a sudden failure. To be realistic, I assume there will be zero maintenance/inspection of this deck and therefore, I wouldn't want to design something exactly like this. I would want some additional redundancy built into the system somehow. I should also add that I'm somewhat low on the risk tolerance spectrum, especially where concrete is involved.

I get the comments about putting a hot tub on the deck but not everybody would consider putting a hot tub on the deck; a small table and two chairs works well for many. Should every deck be designed explicitly for a hot tub install?

Code doesn't require that decks be designed for hot tubs. Depending on which code you're required to follow, the deck live load is likely either 40 psf (IRC) or 60 psf (ASCE 7) assuming this is a residence. Generally, I design for 60 psf. If it's known up front that a hot tub will be installed, an engineer would obviously design for that. If a homeowner decided to add a hot tub later and didn't engage an engineer, there's a good chance the deck would be overloaded and in the worst case could risk collapse.

While a small table, two chairs, and two people is probably the most loading a deck like this will feel on a normal basis, it's nowhere near what code requires. With the 40 psf live load, assuming this deck is something like 8 ft x 16 ft, this would amount to (26) 200 lb people standing on it. Or with the 60 psf loading, it would be (38) 200 lb people!

 

[GeorgeTheCivilEngineer]

I get the comments about putting a hot tub on the deck but not everybody would consider putting a hot tub on the deck; a small table and two chairs works well for many. Should every deck be designed explicitly for a hot tub install?

It's a reference to a meme where hot tubs have been put on some very questionable locations.

 

[ghostdigital]

State of maintenance will matter years from now..

 

[LittleInch]

This video was posted over two years ago so not sure what purpose any notification would pose.

Agree it looks a bit high risk for everything to hang off four bolts, but the highest risk was probably at the first big party which is now long gone....

 

[JAE]

Agree it looks a bit high risk for everything to hang off four bolts, but the highest risk was probably at the first big party which is now long gone....

Well to me the highest risk is the next big party after the concrete around those "iffy" J bolts gets cracked and deteriorated by freeze-thaw action in Columbia, Missouri.

 

[human909]

Well to me the highest risk is the next big party after the concrete around those "iffy" J bolts gets cracked and deteriorated by freeze-thaw action in Columbia, Missouri.

Agreed. Plenty of structures have withstood design loads for a long time before they fail catastrophically. I could link hundreds. But I'll just link this:

 

[Ron247]

His "150 pound" comments are certainly made in jest. His talk about the design appears to be rather detailed and he seems to be very engaged in the details way beyond of how the structure looks.

I agree he may be joking, but he never indicates he is joking verbally or by expression. He may think, 'I joke about my weight all the time in these videos", but we have not seen his prior ones. Plus, he did it twice. But in the end, that had nothing to do with our comments on the structure. It does bother me he jumped up a little, then said "Study as can be". It is not sturdy as can be, he may consider it sturdy for a cantilevered structure but not me. Also, as I stated before, it deflected down as he walked out to the corner, but we did not get to see that, only the movement from the bounce he did.

why many have said this design obviously had no engineering oversight. Is it because the structure is fully dependent on the 4 anchors resisting rotation or the potential for bounciness or what?

The first thing most of us noted was a combination of the lack of redundancy coupled with an unknown amount of embedment of the anchors. We cannot read all the anchor info, but by scale, the anchors are about 8" deep. That is not much embedment for a 3/4" anchor bolt. I am old school 17 to 19 diameters of embedment for tension. It is not that failure of all 4 bolts leads to a collapse, the failure of 1 bolt leads to collapse. The overturning is pulling straight up on the 2 anchor bolts towards the house and the other 2 are somewhat along for the ride. But if one breaks, the other follows suit. Then the other column follows that. It will be quick, not gradual. You will have no warning. Also, if they are A307, they may be good for about 9 kips tension each. Based on the lack of redundancy, I would not want more than 50% stressed under the worst condition.

As far as a hot tub, someone adding a hot tub should consult an engineer, but you cannot make them. Here is the problem though. Let's say anchor bolts are not designed 100% right but they work so far, and I am constantly encroaching into a typical 1.6 FOS. Owner adds a hot tub and while using it, the anchor bolts pull loose or snap and the deck collapses and hurts someone. I assure you; an engineer investigating will point out the flawed anchor design and lack of redundancy. The designer will still get in trouble, even though they never said it could have a hot tub on it.

Now the bounce I commented on earlier. I have been on multiple shaky decks. It sucks. Also, you never have any idea what will happen one day to cause a quick overload. Assessed one with a really weak handrail system that overlooked a golf course. The Owner selling the house complained about my evaluation and told me how there is never more than 6 people on the deck at one time. It was 12'x30' while this one is 8'x16'. There were 2 women putting at the hole nearest the house. I asked him if he had 25 friends inside his Great Room off the deck watching the Super Bowl and those 2 women got into a knock-down drag out fight, what would his friends do? Stay watching the Super Bowl or watch the fight? He had to admit they would come watch. I told him yeah, and they would lean against this rail as they did. You just never know.

 

[Ron247]

I am not a PE so I don't know what potential professional censure could occur, so I am missing why any of you who see a grave failing in the design do not personally contact Mr. Baczek and point out your observation(s). The Citicorp building errors were pointed out to the design team and the outcome was a win/win. I see some passive/aggressive suggestions of sending an anonymous message. If there is an obvious concern why must a message be sent anonymously? I ask this as openly as my username is my name.

This may sound silly but here goes. So far, no one has done a truly intense review of this. Even the model that Az did, was very preliminary. In my state, if I was to truly review this (not speculate) I have to contact him first. I can speculate all day but not do a truly technical review. Also, this would be what I call a bunch of "Responses to Responses". He could get mad first, call my PE board (as noted before) complaining I was trying to practice in MO where I am not licensed. In MO and any other state, I have no standing as an engineer. It does not mean he would succeed in getting me in trouble, but could try. I then must respond to my PE board, and then another response, . . . . In short, his response sets the tone at that point. It could be Thanks, or Who the hell are you to question me?

My concern has been mostly serviceability and longevity. I did not like how he dismissed the deflection by saying "Sturdy as Can Be" and would prefer he said "The calculated deflection under full load is X inches". I always do that to let my client know I cannot make it 0 inches (i.e. Sturdy as can Be)

I saw the bolts, did not comment but would like to know how much they embed before I would.

Also, about the design loads versus real life. I have seen teenagers and adults both see something shaky or shackly and then laugh as they amplify whatever the movement is. In high school, I participated. Alcohol was generally involved, but again, let one of the kids that get hurt from the stupidity be a lawyer's kid, see what happens.

 

[Greenalleycat]

@Brian Malone there are a few key principles that this design obviously violates

1) avoid brittle failures - if those bolts fail by pulling out of the concrete due to minimal embedment, it will be brittle i.e. sudden, no warning, no reserve strength

2) provide redundancy
By nature, a cantilever deck has basically zero redundancy - the bolts are highly loaded so failure of 1 single bolt will cause the whole structure to collapse

1) and 2) are particularly relevant with something like anchor bolts that are cast in...once they're in you have basically zero ability to observe them, maintain them, or upgrade them
They are there, permanently loaded in tension due to the cantilever, and are subject to weathering for as long as the deck exists
Bolts are cheap...why not just embed them 500mm+ into the foundation?
Or better yet, use a weld plate with cast-in reinforcement

3) load paths
The bolts are shown as 12" long but, allowing for the nut + thread extension above, plate thicknesses, and the J-crank reducing depth, I guess it's 150-20mm embedment (scales as 150mm by my estimate)
This is not very much and is less than it should be
The foundation LOOKS super strong due to the steel but the limiting factor is actually the bolt embedment as it barely reaches the steel cage
There is insufficient development length of the reo above the bolts to be confident of confining the bolt pullout failure cone

4) bonus - the foundation looks dumb
They've put a column on the front of what I assume is their standard detail...but the stirrups in the column stay within the column
I would have extended them to the back of the pile



5/ The footing looks really undersided for the overturning load

6/ I'd put money that whoever designed this (or did not design it and just drew it) did not consider the load combination of handrail loads + live load on the floor

 

[Brian Malone]

Greenalleycat (& Ron247) - very clear explanations - thanks! I've looked at some of the earlier posts and some do explain their concern(s) more than just saying the design is bad. So with the deficiencies noted, how is such a plan approved for construction? Is the local building department responsible for some type of plan review/approval? Or is single-family dwelling construction a wild-west, less constrained field?

Ron247 - excellent explanation on the potential hazard/hassle of even a good-intentioned contact with Mr. Bazcek.

 

[human909]

Greenalleycat - very clear explanations - thanks! I've looked at some of the earlier posts and some do explain their concern(s) more than just saying the design is bad. So with the deficiencies noted, how is such a plan approved for construction? Is the local building department responsible for some type of plan review/approval? Or is single-family dwelling construction a wild-west, less constrained field?

I don't know how it is in your field but for many of us structural engineers have limited if any proper review of depth of our work. For residential in here in my state in AS reviews are non existent there is paperwork and submissions involved but the building survey reporting to the local authorities has no idea about the veracity of your engineering.

I do industrial work, structures and equipment involved in processing and manufacturing of good. Here reviews/oversight/approvals is even less onerous than residential!

Reviews/oversight/approvals are generally come done to a companies own risk management which might be quite rigorous internally. But ultimately things get outsourced and it all comes down to ONE engineer and one SIGNATURE for some 'items'. This can include work for some of the biggest mining companies out there or disaster critical structures.

Of course things vary by jurisdiction, but so many times it just comes down to open person putting their reputation/livelihood/freedom on the line, assuring that the design is suitable. If you screw up badly then you could sued or potentially criminally charged if your screw up badly enough. (*or worse, just ask the the wives of the engineers involved in the launch of the North Korea ship recently!)

 

[Brian Malone]

Human909 - I design lab analysis equipment and previously various industrial processing equipment. None have life-support or life-hazard aspects so the oversight is through industrial safety agencies such as UL/TUV, etc. The level of scrutiny is based on factors such as, stored energy, shock hazard, ionizing radiation, crush hazards, biohazard exposure, oxygen service, etc. I understand better the situation that has been discussed with the deck, especially the potential for loss of structural integrity due to aging and corrosion. Very interesting points made by all!

 

[Ron247]

Is the local building department responsible for some type of plan review/approval? Or is single-family dwelling construction a wild-west, less constrained field?

Where I have practiced, the drawings are never reviewed. The city looks for a PE or Arch stamp, and if it is present, they file them away. Even on site visits, they rarely check specifics. I have seen 6'x6'x18" foundations be constructed as 4'x4'x12" and never get questioned. 30 of them, not 1. The contractor intentionally made them smaller, but knew he would not get called on it. He saved a lot of money and time.

For numerous reasons, I have a real problem with Archs being allowed to stamp structural designs when they lack the level of training we have to have. Here are 3 examples of why:

1. While waiting to see an architect, I saw the drawing a really old Arch as working on. There was a W6x20 beam spanning across a long Great Room with a roof brace coming down on the top of it. Nothing framing into the side for stability, just 1 beam and 1 brace. I asked him if he was sure the beam was large enough to clear span that distance without buckling or deflecting too much. He laughed and showed me how easy it was to design beams. Take the moment and divide by section modulus. If it is less than 20 ksi, good to go. When I asked about unbraced length and deflection, he said they did not matter. I advised him to have someone double check his work. My problem, the old geezer was the dad of the Arch I was about to meet with for some work. Based on his age, he has probably designed at least 300 beams like that. He also missed the fact the beam that the brace was supporting was 2-span continuous.
2. Met with an Arch about numerous issues on one of his designs that he stamped the structure on. The first one was the connection of a cantilever beam to a girder. See the picture below for an idea of what it looked like. The problem is obvious. The connection is NOT capable of resisting much moment and all cantilevers have a moment at the connection. He laughed and showed me how easy connections are to design. Take the shear and divide by 13. Round up. That gives you the number of 3/4" bolts needed. Done. When I asked about the moment, he said that did not matter and thinks I was the ignorant one.
3. And my favorite, while arguing with an Arch I was working for about whether something could or could not be done, I would explain with details why it could not, he just kept saying it could, but providing no insight as to why he thought that. He said to me; 'I guess I wasted my time taking a 3-hour structures course when I was in Architectural school. I told him, "Wow, you mean I could have gone to where you went to college and taken one 3-hour course rather than a 4 year Civil Degree with a Masters that specialized in Structures? Now I feel stupid and wasteful". That was our last project together, the next time he asked, I said "No", after all I had not had time to go take that Architectural Level Structures course where he went to school." The problem is, they think passing a 3-hour INTRODUCTORY level structures course means they KNOW structures. No one bothered to tell them, "And here are the 10,000+ things this basic course does not cover".

 

[Greenalleycat]

I don't know how it is in your field but for many of us structural engineers have limited if any proper review of depth of our work. For residential in here in my state in AS reviews are non existent there is paperwork and submissions involved but the building survey reporting to the local authorities has no idea about the veracity of your engineering.

I do industrial work, structures and equipment involved in processing and manufacturing of good. Here reviews/oversight/approvals is even less onerous than residential!

Reviews/oversight/approvals are generally come done to a companies own risk management which might be quite rigorous internally. But ultimately things get outsourced and it all comes down to ONE engineer and one SIGNATURE for some 'items'. This can include work for some of the biggest mining companies out there or disaster critical structures.

Of course things vary by jurisdiction, but so many times it just comes down to open person putting their reputation/livelihood/freedom on the line, assuring that the design is suitable. If you screw up badly then you could sued or potentially criminally charged if your screw up badly enough. (*or worse, just ask the the wives of the engineers involved in the launch of the North Korea ship recently!)

One of the big learnings I've had from this forum is that the way NZ does structural engineering is not how the rest of the world does it
We are very involved in almost all of our projects, with lots of site visits and final sign off required from us before the Council will issue their Compliance certificate at the end
So, we would have been on site to check those bolts + the reinforcement in the footing if we had designed it

 

[Ron247]

If there is an obvious concern why must a message be sent anonymously?

A friend of mine and I noted another issue that has not been mentioned before. He sent Steve an email asking if the shim in the center of the baseplate was removed prior to grouting. He works with structures but is not licensed. He complimented the appearance twice I think in his email. The friend gave a very brief explanation of why he was so concerned that he felt he should contact him. He requested Steve to respond and let him know if it had been removed so he could put the issue to rest in his mind. The entire response was ‘It was removed”. That seemed strange to me when I saw the response. No, thanks for your concern, thanks for giving me a heads up, thanks for having my back, yes I did remove it because I knew it would create a problem or thanks for the compliment on the appearance, just “It was removed”. Maybe he was very busy but wanted to respond, we have no idea. He did not mention this thread and I would not have either at this stage.

Connections like this are one of the harder ones to design. A lot of parameters, mixing of materials of different strengths and different codes. We hope he truly removed the shim but he was given a heads-up on that issue. Someone who already knows about the ramifications of the shim being present, should know about basic embedment lengths, length of rebar needed to develop strength and other parameters more common than the presence of a shim. These are generally in any book on the subject, whereas the presence of shims is probably never mentioned, we just have it trigger something in our mind when we notice them.

Honestly, we have no real idea what is really there in the field, this is speculation at best in some areas, but some items are definitive (such as no redundancy, but redundancy is not an absolute requirement to my knowledge).

Rotation highly controls this connection design. The shim is one thing that appears minor if you are considering vertical loads, but when considering rotation, it is much more critical. The drawing does not show a leveling nut on the baseplate and the pictures do not appear to show a leveling nut, yet there is a gap between the baseplate and the concrete footing. Something must be holding the 2 apart, and it is not grout since no grout is visible. In one portion of the video (6:30 into video) you can see shims present. The shim in the middle of the column appears to bear on the steel but the ones at the side of the column away from the house appear to have a gap between them and the baseplate. They may be just lying on the footing. They are a stack of thinner shims.

In other pictures (4:50 in), you can clearly see the shims on the side away from the house are not there anymore, but there is no grout and the gap is still present and the hoist has been removed from the deck. So, we are assuming the center shim is still there. At 35 seconds into the video, you can see a shim in the center of the baseplate. It would have been twice as good to use shims at the side away from the house only, rather than in the center. No shims are needed on the side towards the house, that level is controlled by the nut on top of the plate due to the rotation direction. If I knew all of that, why would I put one in the center that later will be VERY hard to remove? Whatever tension is placed on the bolts due to dead load will be twice the magnitude due to the short moment arm. You cannot reduce this tension without prying up on the opposite side while grouting and allowing the grout to cure before releasing the prying mechanism. Now, how hard the grout gets “packed in” matters a lot if there is already a loaded stout steel shim in direct bearing. At a minimum, the tension load due to DL is twice what someone may have estimated. If the shim still controls rocking after the grout is installed, the moment arm is still cut in half (or at least reduced), thus increasing (up to double) the tension in the bolts from LL. They may have wedged the outside prior to grouting, removed the center shim, grouted professionally, removed the tapered wedges after the grout cures for several days and touched up the grout. We have no way of knowing. But this would be VERY difficult to do since the shim appears to be in the center of the plate.

Are we correct about what a shim does to the moment arm?

As far as having some redundancy, they could have cast an embedded steel plate into the vertical foundation face and attached to it with a strap or gusset.

In his video, he says anchor bolts “deep” into the footing, but what is visible to us is not considered deep. He also is reading off his call-out for the 12x4 tube. He refers to it as “High-Strength Steel” which I assume is the HSS on his note. HSS stands for “Hollow Structural Section” and is the standard notation for calling out a hollow tube. Small things like this increase concern.

 

[Brian Malone]

Ron247 - thank you for the very detailed discussion! I get why the seemingly reasonable deck (to a non-structural observer) caught the attention all the structural engineers! It is disappointing Steve Bazcek did not respond to your friend's inquiry about the shim. Certainly, he has his reasons but as I mentioned, the case of the Citicorp Center building in New York , the design team evaluated the inquiry about a possible design flaw, saw the merit and successfully remediated the structure.

Going through the details you have elaborated on, and see what others have posted has made me have a different view of the deck anchoring - yeah, too minimalist/spindly to ensure safety over time and under reasonably expected conditions of abuse/misuse. Definitely an eye-opener!

 

[Ron247]

Going through the details you have elaborated on, and see what others have posted has made me have a different view of the deck anchoring - yeah, too minimalist/spindly to ensure safety over time and under reasonably expected conditions of abuse/misuse. Definitely an eye-opener!

Longevity of our designs is the hardest thing to predict because it takes so long to learn about time related issues in our designs. Having misconceptions about what we are doing that we find out later were erroneous is a problem. By the time you find out, you have done 30 under similar bad misconceptions. While he did respond to the inquiry, his answer was so blunt, we were a little amazed but as I said, he may have been busy. I easily give him the benefit of the doubt. We just did not see why someone would put a shim in a place that was so hard to remove, if they know they have to remove it.

I can assure you, I have made mistakes in the past, just not sure what they all are. We forget a word in a specification, transpose numbers and many other "human errors" in addition to design misconceptions. We learn some via others, and sometimes they are either wrong or communicate poorly what they are trying to explain. That is why this forum is so good. You get a variety of viewpoints, experiences and insights.

The deck could be removed, modify the frame/foundation to provide additional support and then put the deck back in place.