Earthquake

Thus far, I have mostly steered clear of posting about topics involving issues of current popular interest (my remembrance of Qudrat was an exception). I am an avid follower of news stories, from local happenings to events of global significance, however, there is usually not much in the daily laundry list of woe and tribulation that I would categorize as constructive or creative. The recent earthquake in South Asia, though, is something that has been very much on my mind and there are a few things that I would like to say on that subject, both from a personal and a professional perspective.

It is always difficult for me to watch news reports of great tragedies. I tend to empathize very much with those who have died and with the survivors who have lost their loved ones. Certainly, I am not unique in this capacity. I am joined by many other decent and caring human beings who do what they can to try and relieve the suffering of those who are in need. For me personally, I usually send a donation to the Red Cross. As I mailed my check a few days ago, I thought of a particular story that I had heard earlier in the week about a little girl in Pakistan whose body was recovered from beneath the rubble of her school. The story was quite brief. There were no survivors of this school's collapse. In all, about 50 children perished. The report mentioned, almost in passing, that a little girl was found wearing a light green dress. As I listened to the report, I began to imagine a young girl of about six years of age. I saw her mother helping her daughter to dress for school, selecting the green dress and thinking how pretty her daughter would look in it. I saw her mother carefully preparing a meal for her daughter's lunch at school, while her daughter ate the tasty breakfast that her mother had cooked to start her family's day. Perhaps the girl's mother walked her daughter to school that morning. I wondered what they talked about along the way. I imagined the mother giving her daughter a loving hug and kiss goodbye when they reached the school's entrance, along with some gently spoken advice to listen to her teacher and be a good girl. I could not imagine all this without feeling a great sense of sadness for this little girl, and also for her parents, especially if one or both of them survived.

As some of my visitors already know, I worked for a number of years as a structural engineer. It may not seem very likely, but cities such as Indianapolis, which are not particularly close to any known earthquake faults, still require that structures be designed in accordance with the established rules of seismic design set forth in various building codes. Therefore, I always included a set of seismic calculations for every building that I designed. Seismic loading is one of several types of lateral loading that may require an engineer's attention (among others are wind loads, hydraulic or fluid loads, and earth pressure loads). Seismic loads result from the inertia (resistance to movement inherent to a mass that is at rest) of the structure itself. An earthquake induces a lateral acceleration to the base of a structure. The inertia of the upper portions of the structure resist the motion of the base of the structure. This causes the base to move faster than the top which induces stress in the structure's beams and columns. Earthquakes, as depicted in movies, usually show tall buildings swaying back and forth until they fall down. This type of motion does commonly occur during earthquakes (although not usually to the degree shown in the movies!). As the forces induced by an earthquake in a building are a function of its mass, it is logical to assume that if the mass of the structure is reduced, it might be less susceptible to damage. This has indeed proven true, and in the past few decades, large structures near active seismic faults have increasingly been designed with steel as the primary structural material, replacing reinforced concrete that was more commonly used in the past. Steel is not only capable of carrying higher loads per unit volume of structure, it has the added advantage of being highly ductile; i.e., it will bend without breaking. This characteristic of ductility will allow a building to sustain damage from an earthquake, yet remain standing to greatly increase the chances that its occupants will survive.

While well engineered earthquake resisting structures are commonly available for public and private use in the U.S. and other developed countries, this is unfortunately not the case for many of the remaining countries of the world. The same magnitude of earthquake that has killed tens of thousands of people, such as last year's earthquake in Bam, Iran and this recent earthquake, would probably only kill a few tens of people if it occurred somewhere in California. The difference is in the usage of building materials and the degree to which they are properly reinforced. Hundreds of millions of people in Iran, Afghanistan, India, Pakistan, and other neighboring countries live near potentially severe earthquakes. Very commonly used building materials in these countries include stones and mud bricks. These materials are usually assembled into buildings with little to no reinforcement to resist the lateral loads of an earthquake. Also, these materials have a lot of mass. Thus, it is no surprise that the death tolls are so catastrophic when an earthquake hits. One thing that surprised me about the schools in Pakistan that collapsed was that they were constructed out of reinforced concrete. This implies that engineers were actually involved in the design of these buildings. I wonder if the collapse of these schools is due to negligent engineering, shoddy construction, or some combination of the two? In any case, most of these deaths would be preventable, if only the people in these countries can be introduced to some different methods of construction using better reinforcement or lighter materials. Also, these methods need not include the services of expensive structural engineering consultants!

There are some available lessons to be learned from methods of construction in other less developed countries. Where materials such as wood or bamboo are in common use as construction materials, earthquakes tend to not claim many lives when they occur. These materials are lightweight and flexible. Thus, they are able to survive an earthquake, often with little or no damage. However, in densely populated countries such as India and Pakistan, there may be very little wood or bamboo available for construction purposes. What little wood is available probably is used mostly for cooking or heating. Even if there was plenty of wood or bamboo available, average people might not use it anyway. A country like Pakistan is subject to great temperature extremes. It can be very hot in the summer and very cold in the winter. Also, temperature extremes between night and day may also be very large. Houses made with thick walls of stone or mud brick have excellent insulating properties. This greatly reduces the need for expensive or scarce fuel for heating and also is helpful for keeping the house cool in the summer. So, it would seem that there is a need for building materials that are either more resistant to collapse or are much lighter and more flexible while at the same time acting as good insulators. There are actually a few possibilities that exist that could provide cheap housing and public structures while also satisfying the above needs.

Over the past several days, I have done some web searching to try and find out what sort of new construction methods and materials are available that could prevent many deaths from future earthquakes if they were implemented on a wide spread scale. I found a very interesting article written by a researcher in India (here is a link) that describes his inexpensive method of reinforcing mud brick houses to better withstand lateral loading. Much of his reinforcement consisted of strips of chicken wire and pieces of bamboo embedded in mud mortar. He tested a scale model using his methods against a traditionally built model of equal size with very encouraging results. His structure was damaged, but still standing, while the other one was destroyed. In a very powerful earthquake, such a reinforced house probably would not survive, however, it might very well remain standing long enough to allow its occupants to exit before it collapsed. Another interesting article (here is a link) describes how blocks of polystyrene (same as styrofoam drinking cups) could be coated with a thin layer of stucco reinforced with chicken wire to form the walls and roof of a house. This would result in a house that would be cheap to build, very well insulated, and also very light weight, seemingly an ideal replacement for traditional South Asian housing. I can only hope that such new methods and materials will be implemented soon!