While big, headline-making demolition projects certainly get our attention, the small ones require just the same amount of “engineering knowledge”. Today, Mark Oakeson jumps on the show to talk about a demolition project he just did. He explains all the details regarding how this type of project takes place in real life, from start to finish.
What You’ll Learn:
- Difference Between Big and Small Demolition Projects
- What Goes Into the Preparatory Work Before the Actual Demolition Starts
- How to Assess the Reliability of the Existing Structure―And Why You Should
- How to Determine the Impacts on the Surrounding Buildings
- The Building Codes and Standards You Have to Follow
- What is a Demolition Plan?
- What Documents Should You Submit to Local Authorities?
- How to Inform the General Public About the Project and Its Impacts
- What is a Precast Double-T Beam? And a Corbel?
- How Seismometers Can Help Your Demolition Process
- Are Demolition Projects as Regular as Other Types of Projects?
- Why Demolition is One of the Most Exciting Projects to Work on
Purple Mattress – https://civilengineeringacademy.com/purple
School of PE – http://www.civilengineeringacademy.com/sope
Resources Mentioned (some links are affiliate links):
CEA’s Video of Parking Garage Demolition – https://www.youtube.com/watch?v=QF04MOunIgo
Episode on Youtube – https://youtu.be/V7IC8XrKYic
International Building Code – https://www.iccsafe.org/products-and-services/i-codes/2018-i-codes/ibc/
AASHTO – https://www.transportation.org
National Precast Concrete Association – https://precast.org
Utah Department of Transportation (UDOT) – https://www.udot.utah.gov
The Ultimate Civil PE Review Course – https://civilpereviewcourse.com
The Ultimate Civil FE Review Course – https://civilfereviewcourse.com
CEA Youtube Channel – https://www.youtube.com/channel/UCPeFLBZ2gk0uO5M9uE2zj0Q
CEA Free Facebook Community – https://ceacommunity.com
CEA FE and PE Practice Exams – https://civilengineeringacademy.com/exams
CEA Newsletter – https://civilengineeringacademy.com/join-our-newsletter
CEA Website – https://civilengineeringacademy.com
Reach out to Isaac – [email protected]
Transcript of Show
You can download our show notes summary here or get our transcript of the show below!
Isaac Oakeson: All right! What is going on, everybody? Mark, welcome back to the podcast. How's life over there?
Mark Oakeson: Great. It's good to be back with you, bro.
Isaac Oakeson: Yes, indeed.
Mark Oakeson: Always fun.
Isaac Oakeson: Mark gets a lot of experience out in the field, so it's always fun to bring him back on and talk about some projects he's been doing. So today we want to talk about demolition. So it's going to be a fun topic as we talk about demolition. Mark recently had a project where he did that. So Mark, why don't you just take us through, kind of high level, what the scope of this project was that you did. And as we talk about demolition, these are just some good pointers for other engineers that may consider this as -- You know, when it comes across their plate to do demolition work. But high level, what's the project you worked on and what happened?
Mark Oakeson: Yeah! So hopefully you can get a little feel for how demolition works. Now, this isn't a huge demolition project. I think a lot of times when we think of demolition, we think of that footage that we've seen on the news where they may be bringing down a big tower, right? And it implodes and it kind of collapses in on itself to a lot of fanfare and spectacle, right? And the news is there, and it makes a big crashing sound and dust --
Isaac Oakeson: Probably expecting something bad to happen.
Mark Oakeson: Yeah. While those are kind of cool demo projects, I guess more visual, more coverage, more attention is paid to those types, most of them are pretty simple, you know?
Isaac Oakeson: Right.
Mark Oakeson: And that's what this project was for me. It was fairly straightforward. We were hired by an office complex property owner to replace an aging parking structure that was built in 1981-ish kind of era. And what they used was a type of construction called pre-cast construction, which is pretty common these days. And what they used for the primary structural component for the suspended slabs is what they call a "double-T", "long-span double-T".
Mark Oakeson: It's basically a kind of a double beam structure that they precast offsite, and once the footings and the foundation walls have been constructed, they come in with these precast double-Ts and kind of lay them out with a crane and put them all into place. And after you've laid them all out, then you've got a nice parking deck to park cars on. And so this deck had been in service for about 40 years, which is, you know, not bad.
Isaac Oakeson: It's a good life.
Mark Oakeson: Yeah! It's a really good life for parking structure. But there have been some corrosion. You know, this project is in Salt Lake City, and we get the deicing salts on the roads, right? And what these deicing salts do to concrete and reinforcement?
Isaac Oakeson: Just beats the crap out of it. Starts corroding. You got issues.
Mark Oakeson: It beats the crap out of it. So it was kind of falling into disrepair. The property owner was getting new tenants and they were concerned about the -- And then on top of that, do you remember our 5.6 magnitude earthquake that rolled through Salt Lake City?
Isaac Oakeson: Yeah. So right when COVID was kind of hitting and people were working from home, Salt Lake had a nice earthquake roll through too. You know, a lot of people thought it was kind of the end of the world at the time, which most of the world thought. But yeah. We had a pretty good size earthquake, and there was a lot of damage too.
Mark Oakeson: There was. And a lot of our buddies in California were probably saying, you know, "Big deal. 5.6...whatever". For us, it was kind of like, "Wow!". And, you know, along the Wasatch Front, we're capable of some pretty sizeable seismic events
Isaac Oakeson: They keep predicting the big one coming out.
Mark Oakeson: We just don't get them all that frequently. But anyway, so that seismic event kind of exposed some more of, I'll say the structural maladies that this parking structure was suffering from. It suffered a little bit of damage. Some of the connections got shaken and they were cracked. So the parking needed to come down.
Isaac Oakeson: Did the ownership have you guys come and do an assessment on it? Or like, what was the reason why they even investigated replacing it in the first place? It was like, customers, parking tenants that expressed concerns, and that kind of got the ball rolling?
Speaker 3: Yeah. A lot of it was originated from the owner himself. I don't know if that came from complaints from tenants. But the owner recognized that there was a problem.
Isaac Oakeson: Got it.
Mark Oakeson: Which is kind of the way it should work. Owners of properties, like, they should be doing their annual maintenance and, you know, looking at things. And so he recognized it as an issue. And so that's when he approached us and then we looked at it and said, "Yeah. You got a problem here. We can price a full removal and replacement, and here's the price for our services". And he accepted that and we were off to the races.
Isaac Oakeson: Awesome.
Mark Oakeson: Yeah. So that's kind of the background. So we did this a week ago today, where we did the demolition. Now there's a lot of preparatory work that has to go into design work, permitting, structural analysis that has to go into effect before you even start demolishing anything, right? So our first concern is to look at the surrounding. We kind of have an idea of what the structure is doing, right? We realize there's a problem, we understand, you know, where the structural deficiencies are. So we know the building's got to come down. So now we start looking at the surrounding areas. Most specifically, the adjacent office building, right? When you're bringing down a building that's connected to another building, you have to start worrying about shared structural components. Those usually share vertical components, foundation walls, shear walls, and those kinds of things. Luckily for this project, we had completely separate structural systems that were pretty well separated.
Mark Oakeson: So they kind of shared a common foundation wall, but that foundation wall had what we call a corbel that kind of stuck out from the foundation wall to kind of receive these structural, precast Double-T's that I'm talking about, so that they had a spot for those to bear on. Those are actually just bearing on the foundation wall that was shared by the office building. And so we could see that there was that separation there. And then with a few saw cuts we could make a full separation, and then we could peel those Double-T's away from the building and not impact the building, the foundation wall.
Isaac Oakeson: That sounds like a lot of preparatory work on this when you're getting ready for a demo. You can't just go out and demo stuff. I'm just curious, is this other building owned by a separate owner that it was connected to? Or is it all the same ownership?
Mark Oakeson: Same owner, although there was a structure to the north. This was in downtown Salt Lake City. So it's not like a huge dense urban environment like you might see, you know, like, downtown Manhattan, you know? It's a little more spread out than that. But still, to the north, to the west, to the south, there was a lot of nearby structures, that you've got to worry about impacting. And so, what we do is we actually set up little seismometers to monitor the vibration and stuff too. And everything I'm talking about too is part of what we put together as a demolition plan that we have to submit to the municipality. And we're trying to adhere to IBC chapter 33, primarily, in our analysis. Sometimes when you're close to pedestrian areas, you have to provide pedestrian walkways and little structures that can protect any passers by pedestrians.
Mark Oakeson: We were actually on the backside of the property. So pedestrians weren't an issue. It was just monitoring adjacent structures, which there's some homes, some apartment buildings in the surrounding area. And they're actually older structures, you know? Most of that stuff I would guess is, you know, circa 1930 as far as when they were built.
Isaac Oakeson: Wow...old.
Mark Oakeson: Yeah. And so, our overall demo plan has to consider all of those adjacent structures and how we're going to protect them, and how we're going to monitor our vibrations, and those kinds of things. So we actually set up little kind of seismometers to make sure that we're not exceeding allowable tolerances for those adjacent structures as we do our demo. So that's part of our overall demo plan.
Isaac Oakeson: So you mentioned IBC as a code that you used as kind of a guideline. Is there any other codes that you adhere to or look at when you're demoing?
Mark Oakeson: Yeah. So, most of the other codes that I get into are structural codes that help me with kind of the forensics, right? Because as part of our demolition, I have to put demolition equipment. In this case they're little mini excavators with Jack hammers, hydraulic jack hammers, that are attached to the end of the arms. And that's the equipment that I have to put on there. And so to assess whether that equipment can be supported on an old structure, I've got to have some kind of idea what that old structure is capable of holding up, right? What kind of loads it's capable of withstanding? So there's some AASHTO guidelines for bridge work that I follow. But in the National Precast Association, you can do some investigation on the way they used to prescribe the design on old precast. Because I didn't have any contract drawings for this project. It was built back in 1981 and, you know, nobody has those on hand. They're just, they're just [inaudible].
Isaac Oakeson: They had some physical drawings that they weren't digitized, and they're gone.
Mark Oakeson: Right!
Isaac Oakeson: I think every company goes through a little bit of that.
Mark Oakeson: Yeah. When you get projects that are this old, there's just "Where are the drawings?". Nobody's held onto them. And a lot of times it's just because the company that built this structure probably had them and then maybe they went out of business, and who knows where they went. Sometimes the municipality might have them on file, but that's not always the case. So what I have to do is kind of get an idea of what these structural T's are worth as far as loading goes, and then assess whether I can get a piece of equipment on top of it. And that goes into our overall demolition plan, right? So we're trying to build this demolition plan, and we're making all these assessments. And so that was a big consideration. In fact, initially we were going to try to put a bigger excavator with a bigger jack hammer on it, hydraulic hammer. But those big ones, I mean, they can weigh an excess of 70,000 pounds.
Isaac Oakeson: Mark, have you done a lot of demo projects in the past? Is demo a regular thing? It doesn't seem like it's done as often.
Mark Oakeson: It's not as common as, you know, typical new construction. Yeah, for sure. And usually demolition isn't on a more, I'll say, more complicated structure, like we've got here where we have actual suspended slabs and some kind of suspended structure. And I would say bridges fall into that category as well. But they're usually just like, you know, single family homes and stuff that -- You know, you got a new highway that's got to go through an area and some homes have been bought by the local DOT as part of their right of way process, and then they're going to knock them down. There's not much risk in taking those structures down because they're single family homes. I mean, a track hoe with a bucket can take a few swipes at that structure and knock it down. And as long as everybody's out of the way, it's not a big deal.
Isaac Oakeson: So, for those that are going to be watching this, because we will post this on our YouTube channel, Mark showed a video of crew members demolishing this structure. And for those listening to it, Mark's done a great job in trying to describe what we're going to show you. But if you get a chance to jump on our YouTube channel, definitely go check it out. We'll show some video of the actual demo that mark took. And I'm just curious, Mark, as you were out there inspecting this stuff. Were there any issues that came up as you were inspecting things? What kind of things were you looking for?
Mark Oakeson: Yeah. So once I had my demolition plan put together, right? So I had gone back and I assessed, "Okay. This is what I think these structural T's, how much load that they can carry". I had determined that a typical excavator was too heavy for these things. So our team came up with using mini excavators, which are only 21,000 pounds each. And I estimated that we had plenty of sheer capacity to support a mini-X, right? So that's what we decided to go with. It's just a couple of mini excavators, and you'll see that on the video. And part of my demolition plan was to have those kind of at the edges of the beams, the two ends of the beams where the sheer capacity was the greatest. That's where I kind of wanted these mini-X's to be confined as far as how far away they were drifting or traveling from the edges, just to minimize the amount of moment that I was inducing into these beams.
Isaac Oakeson: That's amazing because I think when you're watching the video, people might be thinking, "Well, this isn't a huge, demo because you've got these small excavators out there". But really you put thought and engineering into making that a decision.
Mark Oakeson: Yeah. Because I've got crew members that are on top of this thing that they are tearing down, right? And so it's almost like they're undermining the supporting structure that's actually kind of holding them up, you know? And it's dangerous. If this stuff comes down, you know, not only we lose equipment, which doesn't matter in the face of losing somebody's life, you know? That's what I'm really worried about. And so it's very easy, and you'll see in the video, there's -- I mean, as these guys were chipping these structural members apart, they're always bearing on a sound structural T that they're not demoing, right? So they're standing on a structurally sound double-T, and then they're reaching out and breaking apart the one that's, like, right next to it. So you're worried about those tracks and the load from that mine-X's just being on a sound structural double-T. They can basically undermine their supports, right? And off they go over the edge.
Isaac Oakeson: Were these all items that you hit and tell board meetings and discussions with your crews, obviously before they get out and start tearing this stuff apart? Is there other details that you had to go over to make sure they're safe?
Mark Oakeson: Yeah. Well I get my demolition crew, we have a pre-construction meeting or a pre demolition meeting, and we just discuss what the game plan is here. So I've got experienced superintendents that have -- This job was kind of relatively easy for them. My guys are used to taking down bridges that are over, you know, major highways. I-15 is a major corridor in Utah, Salt Lake City area. And these guys are used to taking down bridges and they have to do it within one night, you know? Where they start maybe at nine o'clock at night and they have to have the bridge taken down by six o'clock the next morning, or we get severe penalties imposed on us from UDOT if we don't get it down in time and so morning traffic can pass by.
Mark Oakeson: So these guys that I've got are used to working under the gun like that. And so this one was actually kind of a nice reprieve from the hat because we had all the time in the world we needed to get this down, right? There wasn't any I-15 traffic that's trying to pass underneath this thing. It was just, "let's just get it down safely, make sure nobody gets hurt, make sure the neighbors aren't too mad at us for making all the noise", you know?
Isaac Oakeson: That's great.
Mark Oakeson: Yeah. And we'll be done. But before we started, yeah. We all sat down and we created a general plan. And then my job was to make sure that the engineering was going to work, make sure that the loads that were going to be supported were going to work, and then dictate what those parameters were as far as the equipment movement, what those parameters were given the capacity of those doubleT's. And then we created a set of drawings and we had a little bit of a write-up that we had to explain to the municipality of how we were going to do this thing. We got it submitted and they approved it. And then we were ready to go.
Isaac Oakeson: So, ust a follow-up question then is, you know, as you preparing this, what stage do you get public awareness involved? What did you have to do to get the public at least informed on what you're doing?
Mark Oakeson: Yeah. So there's actual firms, companies that specialize in public information and distributing public information. And we utilize those guys a lot on our bigger projects. On this one, it was small enough that we kind of felt like, "You know what, we can just go door to door to all the neighbors and just kind of explain what's going on". And we had help from the owner of this project too, because he knows, at least he knows better than we do, the neighbors and those that may be sensitive to what's going on. And we just kind of blanketed the area with -- We had a little informational flyer, a letter that we were given to people that was explaining what was going on, when we were going to start, you know, how long they could expect the process to take, you know? And just those kinds of things.
Isaac Oakeson: It's going to be noisy.
Mark Oakeson: "It's going to be noisy". "You're going to be disrupted on this Saturday morning", you know? "And then throughout the week, we're going to be [inaudible] all of the beams that we've dropped. So there's going to be some more noise", you know? And that goes a long way, Isaac. When people know what's going on, they tend to be a lot more forgiving about tolerating the impact, the inconvenience.
Isaac Oakeson: Or even issues that come up, they know why what's going on. I know I appreciate being informed when stuff is going on around my house. So I imagine it's the same as you scale that up.
Mark Oakeson: So anyway, when I went there to, to do my inspection, you know, I was just basically -- Because my guys, they get their heads down working sometimes, and sometimes it's easy to forget. You know, "Oh, man. I'm getting this excavator maybe a little bit too far in the middle. Mark didn't want me to quite that far towards the edge", you know. I've got to come back", you know? And so my inspection was just to kind of make sure that things globally were being followed as far as our plan was. And the guys did great. But I'm telling you, man, it was an exciting thing to witness. Because I was up on that deck a few times and it was bouncing like a trampoline. Those hydraulic hammers get going and they push down in to the the double-T that's being demolished.
Mark Oakeson: Well, obviously there's a reaction there, right? And it pushes back on the machine. And then that loads, the double-T that they're sitting on, and that constant variation and load and then release, I mean, it gets that deck just -- I mean, It was kind of exciting because you never -- You think of parking in like a parking structure or something, it's usually not bouncing, you know? And if it is, you're worried about it. It was exciting to be up there. And then the other thing I was looking at was the adjacent structure. I was making sure that the separation between the double-T's and the office building, you know, was nice and clean. And there was a brick veneer that was on that building that we were trying to protect, making sure that there wasn't any damage going on with that. Yeah, just kind of making sure that our plan was being followed so that we didn't have any incidences. And so, it went well. The guys did a good job. But it was exciting to see it come down.
Isaac Oakeson: Well, I imagine it's pretty tragic if you do find stuff that that is an issue. So I'm happy that you were able to keep things going and everything worked out just as planned. So that's perfect.
Mark Oakeson: Yeah. Worked out great. It wasn't a big demolition plan, but it was one that's not -- I wouldn't say it's typical, right? I'd say more of a single family home, kind of a dwelling demo, is mostly what we typically see. But it had enough, I'll say complication, to it that made it interesting. And this is cool about engineering in general, and why being an engineer is kind of a cool thing. You can see the practical side of your design, right? Your thought process, your planning, your calculations. You can see them being executed and you can kind of witness whether they work or not, you know? And so that's satisfying to me. And so that was cool about this little project.
Isaac Oakeson: Yeah. That's always satisfying when your calculations and things work out. And that's a great thing to happen.
Mark Oakeson: Yeah, it's a little nervous because your calcs, you know, could be protecting the lives of your guys, right? You're, basically predicting that the equipment that they're going to put on that deck is not going to overload the deck.
Isaac Oakeson: Yeah. There's a reason why you have a professional license and you follow the rules.
Mark Oakeson: And the guys -- You know, my guys trust me. And it's good that they do. It does come with that, you know, level of responsibility that you've got to make sure you got everything covered.
Isaac Oakeson: For sure. Well, Mark. This has been a fun episode. Is there anything about this project or demolition in general that you want to touch upon?
Mark Oakeson: Well, I would just say that it's not anything to be afraid of as an engineer. It's just something that you just need a little experience with. You know, I've had guys that have -- I didn't jump into my first demolition plan, you know, cold Turkey. I had people that helped me understand all of the variables and all of the angles that you needed to look at and consider, so that I got comfortable it. But I would just say that it's nothing to be scared of. If you boil it all down, it's just structural engineering. It's just making sure load paths are taken care of. It's almost like reverse engineering, you know? Instead of constructing something, you're taking it down. But the same structural principles, you know, still apply. So it's nothing to be afraid of. In fact, it's pretty exciting.
Isaac Oakeson: Yeah. I think it would be. Good thing to put, not on a resume, but just your whole job experiences. You probably need to experience that.
Mark Oakeson: Yeah. It's one of the more exciting things that you get to experience in your career. Demolition. It's kind of cool.
Isaac Oakeson: That's great. Well Mark, thanks for jumping on. Thanks for explaining the project and going over some demolition stuff. I think, if you're headed towards the structural engineering path, definitely you're probably going to run into this. So hopefully there's some tips here that you can learn from, or just incorporate in your own engineering career. So Mark, thanks for jumping on again.
Mark Oakeson: You bet.
Isaac Oakeson: All right. See you.
Mark Oakeson: Okay. See you.
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