Earthquake Spectra and Sound Structures
Professor Han Sang-whan (Department of Architectural Engineering)
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Professor Han Sang-whan of Department of Architectural Engineering is an expert in the field of earthquake and structural engineering. “More recently from the earthquake that hit Gyeongju on September 12th this year, there is an increasing awareness regarding the safety of buildings,” said Han. Thus, he has been researching on improving the standards of buildings before and after it is constructed. His recent papers, “Effect of connection rotation capacities on seismic performance of IMF systems” and “Building Height Limits for Steel Intermediate Moment Frames” specifically shed light on enduring an earthquake's seismic power.
Accurate prediction of seismic loading and production
There are three different steps to the research when it comes to evaluating a building’s performance regarding its safety. “First, it is essential to predict and calculate accurate magnitude of an earthquake force when one is trying to build a building at a specific place,” said Han. The research used the program that predicts possible earthquake activities and its effect on other different regions within Korea. It is able to do so as the program considers all the past earthquakes which occurred in Korea, all differing in location and magnitude. With this program model that shows the scale of magnitude that affects farther locations, it is able to anticipate other possible earthquakes and their effects.
Developing an analysis model to evaluate the safety of a building
The next step is also critical, which is to establish a precise analysis model to evaluate a seismic performance of a building. It is important to know whether a structure is capable of enduring the effect of earthquake. “It can be done by an experiment in a lab, but it is hard to do so with large buildings due to its size and financial issues. As an alternative, an analysis model can be used as an alternative to evaluate instead through a computer program,” said Han. It is crucial for the analysis model to be on the point to exactly evaluate other buildings’ performances.
“One of the top priorities of a building when an earthquake hits, is to prevent loss of human lives. Thus, the analysis accurately predict responses of buildings structure subjected to not only small earthquake ground motion but also large earthquake ground motion causing the buildings to collapse,” said Han. Such analysis model is based on the conventional mechanics theory. But the theory itself cannot solely explain the rotation capacities of various factors inside a building due to the complexity of the components and their connections of building. It is therefore necessary to conduct experimental tests for the component of building structures to develop and improve analysis models for every parts of the building.
Last but not least, by using the developed analysis model and seismic force, it is able to evaluate the safety of a building towards an earthquake. The method of evaluating the seismic performance of a building has been developed, which can accurately assess the safety of the building both before and after it is constructed.
Within the flow of Han’s research, the paper specifically contains an experiment on this level, which is evaluating the seismic performance of IMF (Intermediate Moment Frames) with connections having a rotation capacity of 0.02 radian. To put it easily, as mentioned above, it refers to the moment connections of a building and 0.02 radian is a designated minimum rotation capacity of moment connections that was defined by US seismic design standard AISC 341-10(a model standard of Korean seismic design). Through the research and experiments went on, it was observed that the rotation capacity of 0.02 radian could not successfully guarantee the satisfactory seismic performance of IMFs. Thus, the paper suggested the number of rotation capacity to improve the safety standard.
The following research that Han and his co-researchers are committed to is quite promising, as it is currently being introduced to the architectural standards of the US. “We hope our research could later motivate domestic buildings to meet safer standards,” concluded Han.
Yun Ji-hyun email@example.com
Photo by Choi Min-ju
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