Associate ProfessorKoichi Isobe

Affiliation: Graduate Faculty of Engineering, Graduate Graduate School of Engineering (National Land Policy Course, Department of Environmental and Social Engineering, School of Engineering)

Specialized field: geotechnical engineering, basic engineering, geotechnical disaster prevention engineering

Research Keywords: Structural Foundations, Earthquake Engineering, Disaster Prevention, Sustainable Society

Alma mater: Kyoto Seisho High School

Final academic background: Graduate School of Engineering, Kyoto University, Department of Civil Engineering

HP address: http://www.eng.hokudai.ac.jp/labo/geomech/

*This article was originally published in the 4th issue of "Frontiers of Knowledge" and has been re-edited for the web. Updated on February 14, 2023

What made you start your current research?

Collapse of a highway due to the Hyogoken Nanbu Earthquake

Many of you reading this booklet will have vivid memories of the 2011 off the Pacific coast of Tohoku earthquake and have felt the terror of earthquakes. The 1995 Hyogo-ken Nanbu Earthquake was the first time I experienced the horror of an earthquake. I still remember how shocked I was when I saw the collapse of highways and skyscrapers on TV. Until I experienced the earthquake, the existence of social infrastructure such as roads, railways, electricity, and gas was taken for granted and mundane, but these structures are the crystallization of human wisdom. I realized that it supports the lives, property, and livelihoods of people from the ground up. This triggered my interest in the construction and design methods of structures (can you imagine how huge structures such as bridges and dams are built?). This has had an impact on my current research.

Next-generation smart structures to create an earthquake-resistant nation

Laminated steel pipe bridge piers put to practical use for the first time

The technology of laminated steel pipe bridge piers introduced here is based on the lessons learned from the damage caused by the Hyogoken Nanbu Earthquake, aiming to improve the seismic performance of bridges, which are positioned as particularly important civil engineering structures, and incorporates the concept of damage control design. Structural technology. Damage control design is based on an accurate understanding of how a structure will deform during an earthquake. It is a design method that controls the damage of the entire bridge by dividing the roles into the secondary members, concentrating the damage and absorbing the energy, and requires advanced design technology. In addition, since it is easy to replace damaged parts, it is possible to recover quickly after an earthquake, minimizing the impact on the economy. Structural forms that incorporate similar concepts are cutting-edge civil engineering technology that is only a few examples in the world, and are positioned as next-generation smart structures that will realize a sustainable society.

In our joint research with Hanshin Expressway Co., Ltd., we have applied the concept of damage control design to the foundation structure that supports the bridge piers (the foundation plays the role of transmitting force to the hard ground, which is exactly what it is). It is an unsung hero!) and a new structure foundation type that is expanded to apply to the surrounding ground.

Ascertaining seismic performance through large-scale shaking experiments

Rows of highly earthquake-resistant piers with rationalized foundations

This structure overturns the conventional design concept and integrates the bridge piers that are visible above ground with the foundation that is hidden underground, so it is possible to more accurately predict the deformation of the structure, including the ground, during an earthquake. On the other hand, if we can predict the behavior during an earthquake with high accuracy, we can lead to further rationalization of the structure in terms of both dynamics and economy. To that end, highly reliable experimental data and an approach based on numerical analysis based on that data are essential. Recent studies using large-scale seismic experiments and numerical analysis have shown that behavior during earthquakes can be accurately predicted with sufficient accuracy. It was confirmed that it is possible to predict the earthquake, and that the structure has sufficient seismic performance even against large-scale earthquakes. As a result, more and more of these structures are being put into practical use today, and the construction of a nation that is strong against earthquakes is now being realized.

Confronting the growing scale and diversification of geological disasters

Slope failure site on Route 274 (Nissho Pass)
Investigation as a geological disaster investigation team of the Japan Geotechnical Society

In recent years, there have been more and more opportunities to feel that natural disasters are becoming larger due to the effects of climate change. Even here in Hokkaido, the heavy rain disaster that occurred in August 2016 caused enormous damage, and there are still many areas where the effects of the disaster still cast a shadow. Hokkaido, which is a snowy and cold region, has little experience with heavy rains, so it is considered to be a region with a high potential risk of landslides and ground disasters due to heavy rains compared to warm and rainy regions in Japan. Since heavy rains of the same scale are expected to occur in the future, there is a need for measures to prevent ground disasters and reduce disasters in cold, snowy regions. Recent research is based on landslide disaster risk assessment by AI using history of damage such as landslides, topography, and geological information, and forest area data on forest species and tree species on high-risk natural slopes. , estimating the driftwood generation potential in a basin that has experienced landslide damage, evaluating the amount of driftwood captured by each bridge, and trying to evaluate the driftwood disaster risk. Based on these, we aim to improve the accuracy of the risk assessment method for bridge damage during heavy rain and snowmelt season.