51– Hitting the right note: Engineering buildings for earthquakes with Civil and Environmental Engineer Brady Cox

May 25, 2021 Utah State University Office of Research Episode 51
51– Hitting the right note: Engineering buildings for earthquakes with Civil and Environmental Engineer Brady Cox
Show Notes Transcript

Learn about work being done to inform building practices and codes in Utah. Brady Cox examines the structural fallout from earthquakes around the world. His research helps predict how earthquakes will impact structures along Wasatch faults. In this episode, he talks about earthquakes in Haiti, New Zealand, and Utah. He also discusses the ground imaging techniques be developed to better understand what's going on under-construction sites. Brady Cox is a Professor in the Civil and Environmental Engineering Department at Utah State University

Brady Cox: [00:00:00] When I was in an undergrad here, I remember as someone came in and lectured to us and I don't even remember who it was, but I remember what they said. They said an engineer is someone who can do for a dollar, what any fool can do for two. So one of the things that we do to start with is we try and make measurements.

Um, to determine the resonant frequency of the ground beneath whatever we're going to build. So people who are used to maybe a stringed instrument say a violin or a guitar, um, when you pluck a string, it plays a note and you can change the note by sliding your finger along the string and changing the length of the string.

The ground beneath where you want to build has a certain thickness. Okay. Or, uh, an, a certain stiffness above a bedrock. And when the earthquake strikes, it's like plucking the ground and it will resonate and it will play a certain note.

Wyatt Archer: [00:01:06] We can't predict earthquakes and we can't prevent earthquakes, but with some wise engineering decisions, we can prevent our structures from collapsing when an earthquake hit. These wise engineering decisions come from researchers like Utah, state universities, Brady Cox. 

Brady Cox: [00:01:26] My name is Brady Cox. I'm a professor in the civil and environmental engineering department at Utah state university.

Wyatt Archer: [00:01:34] My name's Wyatt Archer. You could be busy putting bubble wrap around that gravy boat in your great grandma's China set. But you are listening to this instead, a podcast from the office of research at Utah state university. Later in the episode, you'll learn more about the techniques Brady Cox uses to understand what's happening underneath a building site.

You'll hear about his work, examining earthquake fallout in other countries and how that information is used to make sure that things are being built well back here in Utah. But before we get to all of that, let's learn a little bit more about Brady Cox. How did the son of a helper, Utah coal miner end up being honored in the white 

Brady Cox: [00:02:15] house?

That's a very, uh, interesting question and long story, all hit. The highlights for you. How about that? So I worked on my bachelor's degree here at Utah state university, and I guess I was an okay student. I, I certainly tried pretty hard, I would say, but I wasn't, it wasn't ever my goal to get a graduate degree of any kind.

Um, during my senior year, I got involved with a faculty member here in the civil engineering department who was doing research on. Earthquakes. So I worked my senior year, um, hourly for this professor, me and some of my friends working on research projects. And then that year there was a big earthquake in Turkey, 1999.

And that earthquake killed about 17,000 people. And a lot of buildings collapsed. There was a lot of soil liquefaction problems, but that was a really crazy earthquake and a lot was. To be learned from the research community. And so my professor here got a research grant from NSF to go study this earthquake.

And he asked me if I wanted to stay and work on a master's degree where we would go to Turkey and study this earthquake. And. You know, he told me that he would pay for my tuition and pay me like a little bit of a monthly salary. And I was like, okay. Yeah. I mean, and I just really got interested in earthquake engineering after that.

And I met some faculty members from the university of Texas when I was in Turkey. And they were like, you should think about doing a PhD. And, uh, at that time I was just like, no way I. I barely got into this master's thing, because someone told me that, uh, you know, essentially if I worked hard and I really just got interested and I ended up going to the university of Texas to do my PhD and I got involved with if a faculty member down there, they did a lot of earthquake engineering and the, I just got into earthquake engineering, very heavily.

One, when I left the university of Texas, I was a new faculty member at the university of Arkansas. They have high seismic hazard in the Eastern part of their state from it's called the new Madrid seismic zone. And I wrote a proposal when I was at the university of Arkansas to the U S national science foundation.

On imaging, the subsurface and measuring resonant frequencies and stuff like that. And I was nominated and my career award. Proposal was selected by, uh, the office of science and technology in the white house to receive the presidential award. And so I got to go to the white house and meet with president Barack Obama at that time and, uh, receive my.

Award from the president of the United States. So yeah, I went from helper, Utah, son of a coal miner all the way to the white house. And it was because of education, getting involved in research as an undergraduate and, you know, thank goodness for good professors who, who kind of, uh, you know, allowed me to get involved in that type of work.


Wyatt Archer: [00:05:36] how would you describe that work to like a fourth grader? 

Brady Cox: [00:05:39] So I study and research and teach about how to design buildings and bridges. So they do not fall down during earthquakes. 

Wyatt Archer: [00:05:53] So if I was to follow you on an interesting day of research, what would I see? 

Brady Cox: [00:05:58] So if you were to follow me on an interesting day of research, we would probably be traveling somewhere.

In the U S or maybe even internationally, um, let's say maybe we would be going to work at a nuclear power plant or at a national laboratory where they're building a new structure. That's going to house nuclear material. And we would go to this location. Let's say we'll pick one, uh, Los Alamos national laboratory in New Mexico.

And we would make measurements. We have sensors that we put on the ground and they. Listen to vibrations. So in the ground, there's a lot of waves just propagating through the ground. And they're from earthquakes, maybe in Japan, they're from the waves crashing on the beach in the Gulf of Mexico or in California, or even Alaska there's wind, that's vibrating buildings.

That's blowing through trees. So there's a lot of vibrations in the ground and we set up these really sensitive sensors. And they can help us decode the information that's propagating through the earth. So one of the things we try and do is figure out what note is the ground going to play. And we have to make sure that the building that's built on top of it doesn't play the same note because then you get something called a double resonance.

And that leads to really massive forces on the structure that will cause it to fall down. Yeah. Yeah. 

Wyatt Archer: [00:07:25] If you're selecting a note for the building, or you're trying to select an like, would you want to pick a note that's in the same chord or do you just want to pick something that's as distant from it as possible?

Brady Cox: [00:07:35] So ideally you would be able to have the building. Resonate at a much different frequency than the ground. And that way they would operate almost independently of one another and not combine to play like a really loud note or the same frequency, let's say, um, Okay. When that happens, then the forces on the structure get to be massive, incredible.

And it's really almost impossible to design the building to be strong enough to resist those. So for example, we would like to build shorter buildings. On soft soils, like out in the middle of cache valley. And we would like to build taller buildings on rock. Um, maybe up here on the bench, like where Utah state university is, for example.

So those are things that we try and do. Now. We can't just tell a building owner, like you can't build a tall building out in the middle of cache valley or the middle of the salt lake valley, because it might resonate during an earthquake. Um, what we can do is we can make sure that we understand the problem.

And then we design the building appropriately. We can do things where we change the resonant frequency of the structure by the materials that we use to build it, by the way we connect the materials. Um, we can even put in what we call base isolators, which will then isolate, uh, the ground and the building, like separate them and allow the building to move independently of the ground.

So there's a lot of games we can play. Uh, but the first thing we have to do is figure out. What frequency is the ground gonna resonate at and what frequency is the building gonna resonate at? And then we start trying to make sure they don't match. Yeah. 

Wyatt Archer: [00:09:19] Is it kind of like noise, isolating, headphones that kind of like have a microphone to like pick up the sound and then deliver like the op the anti sound to that or whatever.

Brady Cox: [00:09:30] No, that's it pretty similar analogy. That's what you would like to be able to do. So if you could build a structure that was like your headphones, it would sense K what the ground is doing in terms of its shaking. And it would try and cancel that shaking out actively. And we do have systems like that.

Instructure's, um, active damping, uh, systems are called. And so that's, that's something that could be done, but that's really only on super high end structures. Yeah. 

Wyatt Archer: [00:09:59] So. Obviously if the federal government or somebody building a nuclear lab in Idaho or New Mexico, they're going to be putting in the effort to make sure, um, that, that building's going to be safe from earthquakes.

How does. Your work find its way into residential homes or smaller scale commercial properties. Like, cause I don't imagine a lot of people wanting to pay for it. 

Brady Cox: [00:10:24] Yeah. It's a battle sometimes. Um, but it's through building codes. So every. Let's say four to six years, depending on building codes, we, we update building codes and we update those a lot for seismic design.

In fact of the things that change in, in building codes, probably the thing that changes the most often are the seismic design provisions, because we're continuously learning things that we need to do. And since we generally don't have a ton of earthquakes in the U S. Every year. We I'm part of a group, um, that goes out and does earthquake reconnaissance.

So we'll go to New Zealand or Peru or Japan, and we'll study the effects of earthquakes that happen in different countries. And then we'll look at the lessons that we learn and we'll bring them back to the U S and we'll say, okay, you know, the last really significant earthquake we had in the U S that was quite damaging was probably.

The 1994, Northridge earthquake, just outside of Los Angeles. We've had some other earthquakes since then, but that's like the, really the last one that was significantly damaging. So it's been almost 30 years and we haven't continued to. We haven't stopped learning since then, what we've been doing is we've been learning lessons from other countries.

We bring those back here and we implement those lessons in our building codes. And that's how they get into the standard of practice. Normal structures. Yeah. Yeah. 

Wyatt Archer: [00:12:02] So my place is just slab foundation built in 2004. How. How would that be built differently now versus like 16 

Brady Cox: [00:12:14] years ago? So I don't know if I could give you exact details about now versus 16 years ago, but I can tell you that the way that your building was built here in Utah would be very different than if it was built in, let's say Texas, because we have to tie the structure to the foundation.

Have, did they just 

Wyatt Archer: [00:12:33] like set it structure on top of the foundation there? 

Brady Cox: [00:12:36] Um, Pretty close. Yeah. I mean, not exactly, but we have to really strap structures to the foundation here in a much more. Prominent way to keep it from being shaken off. Yeah. Is this just 

Wyatt Archer: [00:12:52] like J bolt being put in the car? 

Brady Cox: [00:12:54] So there can be more  but we use them.

Yeah. Something, you know, we have these things called Simpson strong ties. Okay. That's a trademark name, but we use straps that are attached to the foundation and then they come up and they attach to the foundation, not just through the J bolts, like in the toe plates of the. Of the wood structure, for example, but those, the spacings of those bolts and the spacings of the nails and the plywood and the, you know, all of these things are pre previsions.

To resist higher lateral or horizontal forces from seismic activity. And so that's, those are the things that work their way into the building codes. The other thing that's happened more recently with the more recent release it's called ASC seven 16, which is the current version of the building code or the standards that a lot of.

A lot of municipalities use is a lot of this work. I told you about building models and propagating waves up. And we call that seismic site response. And that is now demanded by the code in many more situations since 2016 than it was previously. And so those types of numerical analyses have to be completed for many, many more structures.

Uh, in any seismic, highly seismic, uh, area in the U S 

Wyatt Archer: [00:14:26] you go to other countries and you learn lessons from them to apply to our building codes and practices. Can you pick one and share like just one lesson from those. 

Brady Cox: [00:14:36] So I would say one of the things that we study a lot when we go out is this phenomenon of soil liquefaction.

And if anybody wants to know what that's looked like, looks like just type in Google or YouTube, just type soil, liquefaction. New Zealand. Yeah. Okay. And when you do that, you're going to see all kinds of videos from Christchurch, New Zealand, where the ground liquified over and over and over again, and a series of like six different earthquakes.

And what happens is that the water pressure builds up in the sub-surface when the earthquake hits and it comes back. Bursting out to the ground surface carrying sand with it, and then you get a lot of settlement or buildings will punch into the ground. Buried pipelines will float. And so one of the things we're continuously doing after earthquakes in all these other countries are updating.

The methods that we use to predict what soils are likely to liquefy in earthquakes. So that's something we constantly do after every earthquake we go there and we're like, oh, these soils liquified, okay. Let's study them. And let's try and learn. Would we have predicted that those soils would have liquified?

And sometimes the answer is yes. And sometimes the answer is no. And sometimes the answer is. We would have predicted these soils to liquefy, but they didn't, which is now expensive instead of safe. Because if we're building, let's say buildings here in the cache valley to resist soil liquefaction phenomenon, but the soils here are not susceptible to liquefaction.

Well, that's an expense that gets passed on to the owner somehow. Right? So. When I was in an undergrad here, I remember as someone came in and lectured to us and I don't even remember who it was, but I remember what they said. They said an engineer is someone who can do for a dollar, what any fool can do for too.

So we want to be safe. We want to be conservative and make sure that everyone is. Survives an earthquake, but we can't do that at ridiculous costs and expenses. Like anybody could do that for $2. Can we do it for $1? And that's our goal. Like we're constantly trying to refine our methods so that we're safe, but not overly conservative because as I tell my students a synonym for conservative and our.

World is expensive, right? So yeah, we can design buildings to resist virtually any earthquake, but it comes down to probabilities. Is that earthquake going to happen? Is it worth the cost that it's going to take, uh, to do that? So we kind of have to play this game of accepting some probability of a failure, but trying to make sure that that would be a super rare event.

Wyatt Archer: [00:17:36] A few minutes ago, when you were talking about how houses in Texas, like you're kind of just set on their foundation. Maybe there's a couple J bolts holding it there. Yeah. To me in my head. I'm like, well, that seems stupid. And I'm like, why would like just spend a little more money, but they're actually just being wise because that's all they need there.


Brady Cox: [00:17:54] Yep. And that's all they need. And so there no reason to invest that money, we have to balance the rarity of the event with the costs that it takes to make sure that everything's safe. And so for nuclear power plants, Even though it's rare and super costly. We have to do it because the consequences of failure are significant.

Wyatt Archer: [00:18:19] Yeah. Yeah. So I've heard a fair amount about some of the stuff that LA is facing with earthquakes, like their water lines and gas lines. Like they're trying to like replace them with stuff that would be more resilient in an earthquake. Um, but I haven't heard much about the state of affairs for salt lake city and maybe Utah in general.

Um, What kind of infrastructure, things like that what's happening with that? Are there moves being made or are you trying to get people to start doing stuff? 

Brady Cox: [00:18:49] That's a great question. Um, our, we have really good building codes, first of all, in the U S in general. So we're going to be better off than many countries because of those building codes, but we do have certain pieces of infrastructure that are not.

Um, focused on as much. And those tend to be the things that you just described, our sewer lines or water lines, our gas lines, our electrical grid, and we see that those often suffer pretty significant damage in earthquakes. For example, in New Zealand. Um, a lot of the homes fared pretty well, other than from a problem called soil liquefaction, where they would sink into the ground quite a ways, but they wouldn't collapse.

But every single utility going into that home is broken. Your water lines are broken. Your gas lines broken. Your sewer line is broken. So your house is there. You can live in it like a tent, but you can't go to the bathroom inside. You can't turn on the water and have water come out. And when that happens over a really big area in the city, it might take ISIS people using outhouses in New Zealand and really nice neighborhoods for over a year after an earthquake.

So, and they were sharing out houses with three or four other families from houses nearby. So that takes you back, right? Like that's not. Something that people enjoy. And that's just because we ignored designing the sewer lines so that they were resilient and we will see things like that happen in a big earthquake along the Wasatch front, for sure.

Wyatt Archer: [00:20:34] Um, is there, um, when I compare. In my head. I've never been to New Zealand, but when I compare it to here, I'm imagining there's a lot more water there and it's a lot greener and wetter versus Utah. So in my head I'm like, oh, soil liquefaction, probably. Isn't a big deal here unless you like live out in like Benson right next to the marsh.

Um, but isn't an issue here. 

Brady Cox: [00:20:55] Yeah. Yeah, it is. But like you said, the wetter areas are more susceptible. So in order for soil liquefaction to happen, the, you have to have Sandy type soils, sometimes gravels, but mostly Sandy soils and the water table has to be relatively shallow. Those soils have to be saturated.

So the deeper, the water table, the less likely. At the soil will liquefy. And especially if the water table is deep, the effects of liquefaction, if it does happen, probably will not be manifest on the ground surface. Very strongly it's. Yeah, there were places in Christchurch, New Zealand where the water table was within.

Three to five feet of the ground surface. The same thing in Turkey, the earthquake I went to study, um, shallow ground water, soft, Sandy soils, usually deposited by running water. We have situations like that. So anytime you're close to a river, right. And that river has meandered and we've covered those meandering.

Uh, features up. So there are lots of things that are built on top of old parts of the river that we may not know existed before we channelized it more. If we had a big earthquake in Logan and, or in salt lake city, like there will be soil liquefaction, for sure. Hopefully it won't be as pervasive as what we saw in New Zealand or in parts of Turkey, but we can expect it to occur.

Wyatt Archer: [00:22:21] Um, So we've talked broadly about a lot of stuff, but specific things. Are you most interested in? 

Brady Cox: [00:22:29] Yeah, I mean, one of the things we're working on right now that I really enjoy the work is trying to improve our, we call it 3d imaging. And so you can imagine when you go to the doctor, you perf much prefer non-invasive.

Yes. And by noninvasive tests, I mean, X-rays MRIs, um, ultrasounds. Yeah. Right? These types of things where we can look inside the body and diagnose problems without needing to cut the body open or give 

Wyatt Archer: [00:23:06] you a call 

Brady Cox: [00:23:06] now exactly types of things are definitely invasive. The reason that the medical field is pretty good at it is because like, if you slide into an MRI tube, you can get the sensors and the receivers all the way around your body.

Yeah. So one of the things I'm working on a lot is this sub-surface imaging in three dimensions so that we can see things below the surface, maybe even thousands of feet below the surface that might impact the way that the earthquake shakes the ground. So we image in 3d and then we build numerical models in three-dimension.

And then we use supercomputers to run massive computational analyses in order to predict the strength of shaking on the surface. But it starts with the imaging because we can't run accurate numerical analyses. If we don't know what the surface looks like, what are the different layers? How thick are they?

What is their strength in their modulates or their stiffness and all the way down to bedrock. Yeah. So that's something that I'm working on right now a lot. 

Wyatt Archer: [00:24:14] Yeah. Yeah. So I'm imagining that in 20 years, um, as this technology comes farther, there would be like, Lot specific building codes. Like essentially you could take like something that looks like a lawn mower and you'd just run it over the land and it just kind of like builds you a picture of what's underneath.

And then it's like, okay, because you have these things, your house is going to need this, this, this, and this to like, is that kind of the hope for that technology or, 

Brady Cox: [00:24:42] yeah, that would be great. Um, I mean, it sounds nice. Yeah, because right now the standard of practices is that we bring in what we call drill rigs.

Okay. And we drill into the surface. Uh, the subsurface I should say. And we might only drill down, especially for small structures, 15 or 20 feet. And that's fine for what we call static engineering, gravity loads, but for earthquake. Design that's not good enough. And it gets expensive to drill really, really deep.

We have other tools. We push these things called cones, cone, penetration test, and, um, you know, we have site characterization, but they're all the good ones are invasive. And I, the drill into the ground, we have to push something into the ground and that makes them slower and more expensive. To run. And, and also because of that, you have limited spatial coverage.

You punch a hole here and maybe over here, and then you miss everything in between. And so if you could take the lawnmower approach as you describe it, right, and you could continuously profile and image an area and identify some of the things that would affect the construction, like that would be. The goal of the future.

Yeah. Yeah. 

Wyatt Archer: [00:26:02] If you had, if you could wave a magic wand and get people in Utah to understand one thing about what you do, what would it be? 

Brady Cox: [00:26:11] So if I could get people of Utah to understand one thing about earthquake engineering, it would be that there is going to be a big earthquake along the Wasatch front.

It is going to happen. We don't know exactly when it's going to happen. But we are overdue geologically speaking, and the, the threat is real. And when it does happen, people are going to be surprised at the destruction and people are going to say, Hmm, I wish I would've thought about. This ahead of time. Uh, it's hard to keep that in the forefront of our minds when we're dealing with COVID and we're dealing with, you know, taking the kids to soccer practice and all the day-to-day things in life, but an earthquake is going to happen and it will impact our lives.


Wyatt Archer: [00:27:06] So I put, I know that I. I'm not denying that, but I also forget about that and I go to sleep at night. Um, how do you sleep at night? Because it's your job to not forget about 

Brady Cox: [00:27:18] it? I do the same things and I'm probably unfortunately as unprepared as everybody else, you know, but definitely there are simple things to do.

Um, you know, strapping, heavy things down in your home, tying them to the walls. Um, anything that's gonna tip over a lot of our homes are going to perform quite well, but yeah. A lot of things that are going to tip over in their earthquake. Okay. So think of grandma's, uh, you know, Hutch with all the China plates in it and stuff like that.

I mean, just having all of your documents ready, like if you have to leave your house, you know, or do you have water? Do you have some food? People just think that they're going to be able to go down to Lee's or Smith's and you know, or Walmart. Dinner and get food, but in some, in a big event like that, that stuff disappears ridiculously fast.

Yeah. And you think the government's just going to come in and save you, but when you have a huge tragedy or a catastrophe like that, it takes a while to respond. I've seen it. I've seen it in person. I've talked about New Zealand. I've talked about Haiti and I witnessed in the same year, six months apart.

The same size earthquake in Haiti and the same size earthquake in New Zealand. The earthquake in Haiti killed two to 300,000 people. The same size of earthquake in New Zealand. Didn't kill anybody. Now they still had $15 billion of damage to their infrastructure. And ultimately because of another earthquake, a short time later, that was even smaller, 10,000 people had to move out of their homes.

So they didn't come off. Scot-free right. Like, but engineering makes it difference. Natural hazards don't have to be natural disasters. We can make a difference. Uh, As engineers, if we do our jobs. Right. And if people will listen to the advice that we're trying to give, we can limit deaths dollars downtime in seismic events.

If we're prepared. 

Wyatt Archer: [00:29:32] All right. That was my conversation with Brady Cox. If you enjoyed this episode, please leave us a review and follow at instead podcast on Instagram. Also go back and check out episode five with geoscientists Alexis alt. This episode of instead was produced by me. Why Wyatt Archer? It's part of my work in the office of research at Utah state university.