VOS5-11 Full Episode – Engineering Tsunami Resilience

>>Kanesa Duncan Seraphin, PhD: In this episode of “Voice of the Sea,” we investigate how engineers study and design buildings to withstand destructive forces like tsunamis. We’ll learn about the dangers to Hawaii and the plan for vertical evacuation in Honolulu. We start off with distinguished professor Dr. Ian Robertson.>>Dr. Ian Roberston: Hawaii is somewhat unique in that we face a lot of the hazards that exist around the world more than most other locations. Wind speeds can get high, particularly during hurricanes. We have earthquake hazard, particularly for the southeast end of the island, Maui, Big Island. Less so for Oahu and almost nonexistent for Kauai. On the Big Island, the earthquake threat is as severe as it is anywhere in California. And then we have the usual fires and floods as we saw just recently. The tsunami risk in Hawaii is actually fairly high. WE have frequent tsunamis. I believe over the last 100 years, damaging tsunamis have happened, on average, every seventh year. So, every seven years, we have a tsunami that causes some inundation. Some of them might be minor damage. Maybe in Ala Wai Harbor or Haleiwa Boat Harbor, we’ll lose a pier or we’ll have some boats some smashed together. But we get tsunamis frequently. Fortunately, they’re not of the scale of the Tahoku tsunami. We can get that scale. It’s gonna come from the Aleutians. If the Aleutians sea a 9.0, or 9.1, or 9.2 earthquake on the central Aleutians, that’s gonna cause an enormous tsunami for us. And that, fortunately, has a very long return period. Estimates range from 1500 years to 2500 years. So, the chance of it happening in our lifetime is fortunately very low. But if it were to happen, that’s what our buildings need to survive. My philosophy is Waikiki is gonna be Waikiki until there are no people living on the Hawaiian islands, and I tell the harbor people this as well. There will be a Honolulu harbor as long as there are people living in Hawaii. So, it doesn’t matter how long it takes before the next tsunami happens, Honolulu harbor will be there when the next tsunami happens. I think the main issue for Hawaii islands is we will see effects regardless of where the earthquake is around the Pacific. We’ll see the effects. So, the Tahoku tsunami was obviously devastating for Japan, but it also caused quite a lot of damage here in Hawaii, and we need to be prepared even for those smaller events, locally smaller events, so that we’re ready when the big one does hit us. Tsunamis originate in the Ring of Fire, which is the subduction zone around the perimeter of the Pacific. And so, from a lot of different locations around the Pacific island, we’re faced with the threat of tsunami, as well as tsunamis caused by our own earthquakes here on the islands. Is it possible for us to design buildings to survive these tsunamis? And I think the assumption from a lot of the prior tsunamis had been everything’s gonna be destroyed, so there’s really no point. We just get people out and then we rebuild afterwards. This workshop in 2001 looked at whether there was a possibility of designing buildings to survive, and not just to survive but to allow people to use them for vertical evacuation. Because there are areas on the west coast of the U.S. where the Cascadia subduction zone is what’s gonna cause that tsunami, and that tsunami is gonna hit them in about 30 minutes. After the earthquake, they have 30 minutes of warning to get away from the shoreline. And there are many communities that cannot get away in 30 minutes. It’s Long Beach, and a number of communities up the west coast, mainly Oregon and Washington. The Indian Ocean tsunami of 2004 showed us–there were a lot of videos taken of that event and showed us that a lot of people survived by getting into their hotel, and going up in their hotel and just watching it happen. FEMA’s idea anyway was, why don’t we build buildings? And the Japanese were doing this already. Why don’t we build buildings to survive the tsunami. They obviously need to be taller than the flow depth so that people can use the upper floors as a vertical evacuation refuge. We spent five years back and forth between our lab and the lab at Oregon State University studying numerous different wave loading on different structural elements to see what the forces really were. This is a video taken at the Oregon State University– it’s called the large wave flume. So, the intent in this lab, we were studying two things. First of all, we were studying how does that wave break over a fringing reef, because the reef is very shallow, forces the tsunami to break, and it comes on land as a broken bore. It’s essentially a tidal change. You’re changing from this level of sea to maybe 3 or 4 meters higher, but there’s this white, foamy front that’s coming towards you. And that bore is gonna apply more load to our structures than if it were not a bore, if it were simply a wave.>>Kanesa: You would almost think that by breaking, it would dissipate some of its force or energy.>>Ian: It does dissipate some of the energy, but the clean wave, as a clean water wave runs through the building, the impact is gradual. It starts out slowly near the bottom of the building. There’s not an impulsive force, let’s say. The bore is–it’s not a straight drop. It’s not a straight front. It is gradual, but it’s relatively sudden, and so we find that when that hits a broad structural element, like a wall, the force on the wall–and it’s these experiments that showed it. The force on the wall can be 50% higher if the wave is broken than if the wave is not broken. And then my part of the experiment was a structural wall at the end of this flume with load cells and pressure sensors to measure what the force was. So, here the wave’s coming along the flume. It runs over the reef, it brakes. It’s not a broken bore and it hits my structural wall, splashes up, splashes down, and gets rejected. So, here we see the bore coming in. I have pressure sensors up the center of the wall and I have four load cells on the back of the wall that’ll measure the total force. Our initial assumption was that as the wave hits the wall, we’re gonna get the maximum force. It turns out we don’t. We get the maximum pressures, so you’ll see these pressures will jump as the bore hits the wall. But the maximum force doesn’t happen ’til a little bit later. So, right now the bore is hitting the wall and you can see very large pressures on that section of the wall. But the total force is still very small, and so we keep running, and the splash up goes up the face of the wall. And eventually, when that splash up collapses down on itself, right now, as it collapses down and starts pushing away from the wall as a bore traveling in the other direction, that’s when we get the maximum force. So, we never expected it to be at that point. And those forces are very large, so it’s important that we’re able to design for them. We spent a lot of time working on an equation that would mimic that scenario, that would mimic the incoming flow and the outgoing flow, and developed this very complicated formula. This is the experimental force and this is the predicted force. And if they agreed exactly, they would run up the diagonal purple line. But what we were able to show is that that equation very clearly predicts, both in the lab and in the field, what the load will be. And the advantage then is we can take our lab experiments and scale them up ten-fold to get to the full scale result. So then I looked at whether we could use a much simpler equation and we found that it almost does the same job. It’s a much simpler equation and it gave us these hollow symbols, whereas our fancy equation gave us the black symbols. And so, the code now has the simple equation. WE basically take the drag of the water traveling around the building, though it’s not actually going around the building, and we increase it by 50%. This code does not provide tsunami design for residential structures. Single family, two family, even for timber frame or light gauge steel frame structures, we don’t design them for tsunami. You just take a financial loss. You make sure everybody evacuates, you save the lives, but the houses that are destroyed become a financial loss. What we want to survive are the taller buildings in Waikiki, downtown, in Kaka’ako, because people are gonna use those. We use them now for vertical evacuation from tsunamis and we want those folk to survive. Plus, when you come back to that 20-story building, only the first two or three floors have been damaged, and it’s the non-structural elements. It’s the walls, and the carpets, and the furnishings. So, if it’s a hotel, it doesn’t take long for the hotel to reinstate themselves. So, the resilience of the community is improved. If we design for the initial impact, then the structure will handle the subsequent tumbling. For taller buildings, for buildings that are maybe 20, 30 floors high, the columns and the walls at the bottom of the building from a seismic design are already fairly sturdy and the tsunami’s not gonna affect them at all. There’s not gonna be any financial consequences of adding tsunami design. If it’s only a seven story, eight story building, there might be a little premium we have to pay to add tsunami design. So, if I’m evaluating an existing building in Waikiki that is 30 stories high, I doubt I’m gonna have a problem with tsunamis striking that building. I might have a problem with a shipping container hitting a column, so I may have to strengthen individual columns, but overall the strength of that building is probably going to be enough. But if we think of Honolulu Harbor, those shipping containers are gonna come to downtown, to Kaka’ako, so there’s actually quite a lot of our major buildings are gonna be exposed to shipping containers and possibly ships. If you know a tsunami’s coming, here in Hawaii we have 4 to 12 hours notice, depending on where it’s coming from. Go around and open the bottom, just the bottom container. On Sand Island, the flow depth is probably not gonna get above 3 meters, which is 9 feet. That’s the top of the first container. So, the ones stacked on top, they’re fine. They’re dead weight. They’re holding the bottom one down. But the bottom one, just open up, even if it’s just one end. Just let the water inside. Get rid of the air and that’ll solve your problem. [music]>>announcer: The University ofHawaii’s Sea Grant collegeprogram, focused on Hawaii’scoasts and its communitiesthrough sustainable development,safe seafood supply,sustainable coastal tourism,hazard resilience,and healthy coastal ecosystems.Hawaii’s Sea Grant.[music]>>Kanesa: We’re talking with award-winning engineer, Gary Chock, who was traveled around the world investigating the effect of tsunamis in order to help design new national building codes. We join him in downtown Honolulu at the offices of Martin & Chock.>>Gary Chock: We were the first team from a foreign country to get into Japan after the tsunami. We were there one month after. With Chile, it was kind of the opposite. It was–when we got there, it was sort of–there was a lot of riots, and curfews, and stuff, and then finally it settled down enough and we arrived. In general, you wanna be there as soon as possible, because the clean up process itself removes evidence. If you get there soonest, then–with as little clean up as possible, then you see the whole context of the damage that the buildings sustained. You see other collateral types of evidence, of debris, you know, mud lines are very apparent and such. It hasn’t been disturbed. You’re trying to recreate the scenario in your mind of what that building went through, so you need all these other pieces of evidence to test your internal hypothesis of what you believe you’re seeing. Can you collaborate that with the evidence that’s on the field? We take different kinds of data. One is we’re trying to capture the elevation of the water level. If it’s visible on the building or something else, you’re trying to reference that to some other point that can eventually give you a mean high water, or the water level at that time of the tsunami. You know, we have laser range finder instruments that can help us do that. If we find a good example, we try to take very detailed measurements, because we wanted to take measurements that were sufficient to be able to recreate that building in a computer model to test our hypothesis from the field using a structural analysis. That included, say, climbing into the building, taking measurements, you know, spending a lot of time in the building and getting places where most people would not wanna go to take the measurements of the structure. One thing about Japan that was very helpful was it happened during the day and there were a lot of videos taken by survivors. There was also satellite imagery and a lot of data that researchers were assembling. When you’re there, you’re basically trying to look at essentially what constitutes a full-scale experiment of something that you could never create in the laboratory. And so, you’re trying to find the best example buildings you can to get the information you need.>>Kanesa: So, you want buildings that did not hold up, as well as buildings that survived.>>Gary: You want buildings that survived and you want buildings that underwent some degree of failure, a mode of failure that is very recognizable. Essentially being somewhat like a mobile forensic investigative team.>>Kanesa: So, you’re looking at, like, the composition of the concrete, what kind of steel is it, how much, what’s the lattice of the steel, how close together.>>Gary: Sure, sure.>>Kanesa: What’s the sediment like that it’s built on, that kind of thing.>>Gary: Basically, yes. And you know, as well as overall dimensions and things of that nature. This was, or became in 2016, the world’s first comprehensive tsunami design building code. What we’re hoping is that what we’ve produced will allow communities to start designing new building structures that provide havens of safety locally that they can go to to survive. And when we were in Japan, we saw many good and several bad examples, and we kinda understood the consequences of that firsthand, you know? We want to prevent what happened in Japan. We are–essentially, the requirements and the estimate of the tsunami was way under what should have been done in many cases.>>Kanesa: What types of knowledge goes into being a civil engineer?>>Gary: You better be good at math and you better be good at physics. Those are the fundamentals of engineering. It’s basically applied physics and applied math, and sort of the key to having judgment. When we’re going out to the field, though, talking about viewing things that have clearly defined structural mechanisms that we understood that would be caused by some tsunami effect. Okay, so if you don’t have the understanding of physics, mathematics, or fluid mechanics, you’re not gonna be able to recognize any of these things. You’ll be totally in the dark. So, you might go to the site and you might pick up on some things, but you’ll miss, like, so much. It’s not based on memorization, it’s based on having the understanding of the physics and mathematics. It is really a different way of thinking. I say that basically engineering is the counterculture to most other disciplines. [music]>>announcer: The CurriculumResearch and Development Groupin the College of Educationat the University of Hawaiiat Manoa.CRDG’s training rootsgo back over 40 years, throughprofessional developmentprograms, curriculum workshops,research on teachingmethodology, individualizedschool and district training,and so much more!The Curriculum Researchand Development Group,improving schools,improving education.CRDG.[music]>>Kanesa: Welcome back. We’re talking with Dr. Ron Riggs, Dean of the College of Engineering, to better understand the connection between research and engineering in practice.>>Kanesa: How do you know what types of debris might be hitting buildings or go about even asking–starting to ask those questions?>>Dr. H.R. Riggs: People have been doing post-disaster reconnaissance after tsunamis and earthquakes as well for a long time, and so there’s really three main types I would say, or four. There’s going to be shipping containers, which you may not normally expect, but there’s a lot of shipping containers, especially near the coast. Logs, and telephone poles, and the like are another common source of debris. And cars, of course, can also be, but cars a little more flexible, and so one wouldn’t expect the forces to be quite so high. A little bit more rare would be ships from a harbor could be washed on shore to hit buildings. That certainly happened in Katrina.>>Kanesa: Your work has developed a code for future building, but compare that to the situation that we have now in our current infrastructure. Do we have enough vertical buildings that people could evacuate to?>>Ron: Well, I think that’s not my area of expertise, I have to say, but I think there probably are. It’s just an issue of making sure that they are going to be safe. You don’t wanna tell people, “Okay, here’s a vertical evacuation shelter,” that then is not safe. Now we have guidelines for engineers to go out and determine whether it meets the code or not. Before this, there were no guidelines, no national guidelines for doing this sort of work. I mean, engineers were just kind of left to make their best guesses and so forth.>>Kanesa: So, you have a sensor here. Can you tell me a bit about this?>>Ron: Yes, this is called a load cell. And so, in some of the videos, you’ll see this. The one in the Oregon State flume is mounted on a post and the model of the shipping container hits it. At Lehigh University, there were two of these that the bottom of the container hit. When that shipping container hit, you could feel and hear the sound or the vibration wherever you were in that building, so it was a lot of fun.>>Kanesa: What’s the smallest load that it can register?>>Ron: I’d have to look at the smallest load, but the largest load is 300,000 pounds.>>Kanesa: It’s hard for me to conceptualize what is 300,000 pounds. Can you–>>Ron: Right, so if you think of a shipping container, a 40-foot shipping container, the capacity of that is about 60,000 pounds. If you wanna build a building that’s not going to collapse during a tsunami, you might say, “Well, you know, we can just get everybody out.” If you think of Waikiki, it’s really not feasible to evacuate everybody, so they talk about– there’s two kinds of evacuation. There’s horizontal evacuation where you move inland far enough where you’re not gonna be affected by the tsunami. Then there’s vertical evacuation, and that’s really what the plan is for Waikiki. And the idea is you get into a building that’s going to withstand the tsunami and you get high enough up. So, it’s gotta be a high-rise building. You get high enough up so that you’re out of the water and then just ride out the tsunami that way. So, clearly you do not want those structures collapsing during a tsunami, either from the fluid loading or from debris impact loading.>>Kanesa: And your research is specifically designed to understand how much force the tsunami or the water would bring that debris with to impact the building?>>Ron: That’s correct. So, we wanted to quantify those forces. We wanted to propose a theory for which we could calculate the forces, then we did experiments to validate that theory, to make sure that it actually reflected the real world. Our theoretical model worked so well, it was–the theoretical model was based really on just a very simple structural member, but it actually works very, very well for both a log, we tested a telephone pole to represent a log, and as well as for the shipping containers.>>Kanesa: Can you tell me a little bit about the college?>>Ron: Yeah, the college is one of the–has been a part of the university since its founding, essentially. We have four programs, but we’re expanding into new programs. We cover the three basic traditional engineer disciplines: civil engineering, mechanical engineering, and electrical engineering. So, the electrical engineers, you know, work with, of course, computers and electronics, but they’re also into sensors, and big data, and that sort of things. Mechanical engineers work, of course, with machines, but also with fluid flow is a big things in mechanical engineering, microfluidics. Both faculty in both those departments also are involved in things like aerospace engineering and biomedical type applications in engineering. Construction engineering as well. We also cover transportation engineering, technical engineering, hydraulics, hydrology. As the recent flood’s shown, hydrology’s a big issue in Hawaii. So, it’s a very exciting time for the college. Engineering is a very popular major these days because so much–society’s becoming evermore technological, and so the demand for engineers is very, very high. All of our graduates really have no problems getting jobs. [music]>>announcer: We are looking fora few heroes, mentors,trail-blazers, innovators.A passion to change lives,spark curiosity, open hearts,and awaken minds.Help students answerthe question, “Who am I?”This could be your calling,but this is no job.It’s the journey of a lifetime.Be a hero.Be a teacher.

1 thought on “VOS5-11 Full Episode – Engineering Tsunami Resilience

  1. people can avoid tsunami if they enter into ball like soccer ball zorbung please watch


    people would enter zorb ball and zorb ball outer part is covered in hard rubber so ball does nt brak when hit sharp object and when tsunami hits zorb ball full of air rises to surface people cn exit zorb ball when at surface

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