2:45 PM - 3:00 PM
[O10-04] Devastating buildings Damages and Seismic Design afterwards
★Invited Papers
Keywords:seismic design, seismic-isolation, intensity
The 1995 Kobe Earthquake (M7.2) was the first time that buildings and cities designed according to the seismic design method enacted in 1981 experienced strong tremors of intensity 7. Although I thought I had some understanding of the earthquake-resistant design method based on the experiences of the 1960 Niigata Earthquake (M7.5), the 1968 Tokachi-oki Earthquake (M7.5), and the 1978 Miyagi-ken Offshore Earthquake (M7.4), The damage was a painful experience for us structural designers to learn.
The damage was completely different from the shear failure of short reinforced concrete columns and torsional collapse of eccentric frames. Above all, the collapse of a dilapidated wooden house in a densely wood-framed residential area and the ensuing massive fire. The memory of standing stunned in the smoldering smoke of the burned-out Kobe marketplace is still fresh in my mind. The broken steel box columns of the Ashiyahama high-rise housing complex, the ruptured beam joint, the destruction of the middle layer, the shear failure of pilotis columns in many reinforced concrete apartment buildings, and so on. The damage patterns and severity of the damage were unprecedented in the past.
However, most of the damage was observed in buildings designed in accordance with the so-called old standard prior to 1981, and there was little damage to buildings designed under the 1981 seismic design method, which incorporates the findings of seismic response analysis. Some of the damage patterns have been utilized in subsequent improvements of seismic design methods, contributing to the safety of today's buildings. The fact that buildings with seismic isolation structures, which had only recently been developed and realized, were able to maintain building function without damage to finished components led to the rapid development of seismic isolation and vibration control structures. The unprecedented earthquake disaster drew attention to the importance of full-scale research to confirm seismic performance, and E-Defense has contributed greatly not only to subsequent technological development but also to the understandings of the technology of seismic system among the general public through the media. On the other hand, one of the most noticeable differences that emerged from the earthquake was the difference between the awareness of building designers and the understanding of building users regarding the earthquake resistance of buildings. Although the designers had explained that the buildings were designed to be safe even in the event of a major earthquake, safe only means protection of human life, which is the minimum criterion under the Building Standard Law, and the reality that finished components will be severely damaged and the building will not function was brought into sharp relief. Subsequent earthquakes, such as the 2011 East Japan Earthquake and the 2016 Kumamoto Earthquake, have made it clear that conventional seismic design, in which the shaking is greater than that of the ground during an earthquake, is insufficient to meet the needs of production facilities that support Japanese industry to maintain production equipment and functions inside buildings. For this reason, seismic-isolated structures are often chosen in place of earthquake-resistant structures in semiconductor factories. A full-scale seismic isolation test facility, E-Isolation, was constructed in Miki City and is now in operation, aiming to improve the reliability of seismic isolation structures that absorb seismic energy with concentration.
Although seismic design has always been developed by learning from earthquake damage, it is not impossible to imagine possible damage and injury. In order to protect the future IT society, which will be supported by precision semiconductors, we will introduce not only past cases but also the efforts of world leaders in seismic technologies in facilities such as E-Defense and E-Isolation.
The damage was completely different from the shear failure of short reinforced concrete columns and torsional collapse of eccentric frames. Above all, the collapse of a dilapidated wooden house in a densely wood-framed residential area and the ensuing massive fire. The memory of standing stunned in the smoldering smoke of the burned-out Kobe marketplace is still fresh in my mind. The broken steel box columns of the Ashiyahama high-rise housing complex, the ruptured beam joint, the destruction of the middle layer, the shear failure of pilotis columns in many reinforced concrete apartment buildings, and so on. The damage patterns and severity of the damage were unprecedented in the past.
However, most of the damage was observed in buildings designed in accordance with the so-called old standard prior to 1981, and there was little damage to buildings designed under the 1981 seismic design method, which incorporates the findings of seismic response analysis. Some of the damage patterns have been utilized in subsequent improvements of seismic design methods, contributing to the safety of today's buildings. The fact that buildings with seismic isolation structures, which had only recently been developed and realized, were able to maintain building function without damage to finished components led to the rapid development of seismic isolation and vibration control structures. The unprecedented earthquake disaster drew attention to the importance of full-scale research to confirm seismic performance, and E-Defense has contributed greatly not only to subsequent technological development but also to the understandings of the technology of seismic system among the general public through the media. On the other hand, one of the most noticeable differences that emerged from the earthquake was the difference between the awareness of building designers and the understanding of building users regarding the earthquake resistance of buildings. Although the designers had explained that the buildings were designed to be safe even in the event of a major earthquake, safe only means protection of human life, which is the minimum criterion under the Building Standard Law, and the reality that finished components will be severely damaged and the building will not function was brought into sharp relief. Subsequent earthquakes, such as the 2011 East Japan Earthquake and the 2016 Kumamoto Earthquake, have made it clear that conventional seismic design, in which the shaking is greater than that of the ground during an earthquake, is insufficient to meet the needs of production facilities that support Japanese industry to maintain production equipment and functions inside buildings. For this reason, seismic-isolated structures are often chosen in place of earthquake-resistant structures in semiconductor factories. A full-scale seismic isolation test facility, E-Isolation, was constructed in Miki City and is now in operation, aiming to improve the reliability of seismic isolation structures that absorb seismic energy with concentration.
Although seismic design has always been developed by learning from earthquake damage, it is not impossible to imagine possible damage and injury. In order to protect the future IT society, which will be supported by precision semiconductors, we will introduce not only past cases but also the efforts of world leaders in seismic technologies in facilities such as E-Defense and E-Isolation.