Following the May 12, 2008 M8 Sichuan Earthquake, Miyamoto International and Global Risk Miyamoto immediately dispatched a team to the affected region. Our reconnaissance team is composed of Chris Heaton, Principal of Global Risk Miyamoto, Rocky Ng, engineer from China Rail Way, Tenth Group, Third Engineering Company, and the author, Kit Miyamoto of Miyamoto International and Global Risk Miyamoto.
May 21, 2008
8:30 amThis is the last day of our trip. NHK called and asked to go back to the first middle school in Juyuan Township that we visited on the 18th. NHK wants to do a detailed investigation of the school building for a 90 minute special this Saturday. It is a hard decision since we want to cover as much area as possible. We decide to go along with them. It is a good thing for the public to know what makes building dangerous.
We drive off in two vans. The NHK crew provides lunch; which is a piece of bread and orange juice. We don't eat much during the day because there is just no appetite. With so much destruction, suffering and death, no one is in the mood for a picnic.
11:00 am Juyuan Township, Dujiangyan
We drive into the town of Juyuan; which is fairly close to the epicenter. Walking around, it is evident that the earthquake forces were very much focused in one direction here. Diagonal cracks are found along walls oriented in the same direction for many buildings.
11:20 am
We walk into the grounds of the middle school. I feel like I just came back to the nightmare that I can't escape from. Today, the ground and broken building are covered by white disinfection powder. It looks like fresh snow covering a grave yard.
11:35 am
We walk through the site and examine the twisted concrete and broken bricks to better understand how the building was constructed. NHK provides us with a hand sketch and a picture showing the original state of the school.
12:10 pm
A client has requested a structural survey of their damaged industrial facility. We have to split the team. Chris and Rocky go to do the survey while I stay to continue the investigation with the NHK crew. They have to drive 5 hours to get to the site. The road conditions and our van's shocks are not good. This will be a hard trip for them. It is kind of strange to say 'good by' to them. We've gone through a lot together in the last 5 days.
12:20 pm Anatomy of the collapse:
At first glance, I thought this was a concrete frame building. I see broken concrete beams and rebars on the ground. I can see concrete frames in my mind. But we can't find any concrete columns. The only concrete items we find are the precast floor slabs and concrete beams. After 30 minutes of study, I finally realize that these concrete floors are supported by the bricks without any reinforcement. This is basically an unreinforced masonry (URM) bearing wall structure. The stair structure stands alone. I saw this a lot during this trip. Cast in place stair structures turned out to be the safest place in the school buildings. I heard that children who happened to be in the stairways survived.
As demonstrated by earthquake after earthquake, URMs are one of the most dangerous forms of construction.
Just imagine building a Lego house, but using Lego blocks that have no protruding nubs to tie the Legos together. This Lego house would not be able to resist lateral shaking. The school building is like these weak Lego houses.
To resist earthquake forces, buildings must be designed to support the gravity (vertical) and seismic and wind (lateral) loads. The precast floor planks of this school simply rested on the concrete beams. There is no positive mechanical connection between the slabs, or between the slabs and beams. There is also no structural cast-in-place topping concrete slab to tie together the planks and the beams. The beams simply rested on the brick bearing walls without any mechanical connection. Large windows in each classroom further reduced the amount of walls available to resist earthquake forces. These narrow brick bearing walls made for a more deadly combination.
Between the classrooms are solid brick interior party walls. As noted earlier, if there are many of these solid walls, a building may survive even when the walls are made of unreinforced brick. The surviving lab building nearby has similar brick party walls that happened to aligned with the predominant earthquake ground motion direction. I found a single large, diagonal crack at the ground floor wall. This wall is oriented in the same direction as the walls of the retail buildings that I described earlier. Had the strong ground motion been in the perpendicular direction, this building would probably have collapsed as well.
This earthquake was generated by the nearby Longmenshan Fault, a thrust fault. From the pattern of wall cracks, it appears that the large pulse projected from the fault was perpendicular to the fault line; which runs northeast. So in this area, if a building had many solid walls aligned perpendicular to the fault, it had a good chance of surviving without collapse. But if the walls were narrowed by many door and window openings, a building had no chance. Unfortunately for these 700 kids, the windows ran northwest.
The neighboring dormitory building survived, but with many shear cracks in the walls. This is similar to the surviving apartment blocks we saw yesterday. With small dormitory rooms, the building had many, many walls to resist the earthquake forces.
I describe the above information to the camera. The truth needs to be told. Unreinforced masonry and non-ductile concrete structures again killed many thousands.
3:30 pm.
We finish the taping. I need some time alone and walk around the white powder covered field. I see a man who is at the top of the rubble. He is digging and removing the twisted steel rebar and concrete with his bare hands. There are tears in his eyes. There are still 20 kids missing in this place. I see a pile of kids' backpacks. A couple of women are searching for their children's. They are very upset but determined to find closure.
I see two pictures of young girls in a simple memorial next to the rubble. Nearby is a small tape recorder playing the same Chinese chant that we heard a few days ago. This must be a prayer of some sort. I kneel in front of these pictures for a while. I can't stop crying.
7:30 pm Chengdu
I am now back at the hotel to meet Professor Wada from Tokyo Institute of Technology. He is my doctoral research professor. It is nice to see a friendly face. Professor Wada is one of the most eminent earthquake engineers in Japan. He will be the first engineer from there to visit this earthquake. I've been told that our team is the first foreign engineering team to study this earthquake so far.
Throughout this trip, I found the Chinese government to be very open, organized and competent. I saw the Army, medical personnel, search and rescue teams, demolition and clearing crews, and disinfection specialists working together rapidly. Our TV station friends reported that they had no difficulty at all with performing their activities.
Technically speaking, our findings reinforce old lessons - unreinforced brick, non-ductile concrete, and building elements not tied together well are dangerous combinations in earthquakes. Unfortunately, this lesson is repeated over and over again. This is not a China issue alone. We must retrofit these dangerous buildings worldwide, including those in the United States, Canada, Central and South America, Japan, China, South East Asia, and Eastern Europe. If we do this, then the 55,000+ lives lost here are not wasted. We owe it to these children who died underneath their schools.
May 23, 2008
10:00 am Davis, California
I am back in sunny Davis, California. Sichuan seems like a distant memory. I am attending my 6-year daughter's kindergarten song and dance show with my family. It's really nice to be home with them. As I watch my daughter and her little friends sing together, there is a flashback to the collapsed kindergarten school in Sichuan. Tears start flowing from my eyes...
