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Deterioration and Disrepair of Infrastructure with Age:
Preventive Measures Desperately Required in Response to Risks Bridges Face

Teruhiko Yoda
Professor, Faculty of Science and Engineering, Waseda University

Three of the biggest issues for Japan in the 21st century are said to be creating a sustainable society, responding to the decreasing population, and achieving a balance between the environment and economy. Personally, I believe that it is important for Japan to become a country renowned for both safe and secure longevity and environmental advancement by 2050. Although there are also other important themes, I believe these two themes are particularly important for Japan after the experiences of the Great East Japan Earthquake on March 11, 2011. An essential element for the creation of a sustainable safe and secure society is infrastructure. Japan has an extremely large volume of infrastructure stock. This stock could be thought of as an enormous asset. My specialization is bridges. In Japan, many of these bridges were built during a period of strong economic growth following WW2. The fact is that many of these bridges are reaching an advanced age (see Figure 1).

Figure 1: Japanese infrastructure also reaching an advanced age (bridges over 15 meters in length on ordinary national roads and prefectural roads)

In addition to the advancing age of infrastructure, other issues are coming to the surface, such as the vulnerabilities of infrastructure in face of disasters. Unfortunately, Japan is fated to have to face damage from natural disasters such as earthquakes, strong winds, and floods. Japan is faced with a situation completely different from countries that can get by without giving hardly any consideration to the possibility of earthquakes or typhoons. Accordingly, it is not very meaningful to compare Japan with other countries in relation to this issue. As bridges are not able to move or seek refuge in the face of disasters as we can, bridges are currently exposed to extremely harsh conditions. Accordingly, if we are able to develop technologies to protect most of our infrastructure from major disaster and deterioration and prolong the life of this infrastructure, this means that we will have created technologies that can be used to build up infrastructure anywhere in the world. In this sense, the situation we face now marks an important opportunity for Japan.

On August 1, 2007, a bridge over Mississippi River collapsed in Minneapolis, Minnesota, US. This incident occurred despite the adequate efforts that have been made in the US to prolong the lives of bridges (see Photo 1). I still cannot forget the sense of shock that I felt when I saw the disaster site. On reflection, I wonder whether Japanese road bridges are really secure. In contrast to the US, regular inspections are not conducted for many road bridges in Japan. Furthermore, following the lead of the US, our bridges are rapidly reaching an advanced age. Our road bridges face the double burden of being uninspected and rapidly aging. Furthermore, these aging Japanese road bridges are subjected to traffic by trucks exceeding weight limits. While structures like bridges can withstand traffic by massive, heavy vehicles while the structures are still solid and sound at a young age, this does not necessarily apply as structures age and deteriorate, just as is the case for human beings. Of course aging and deterioration are not one and the same thing. There are many solid and sound bridges that have been around for close to 100 years.

However, the reality is that most of our bridges are becoming worn out. We need to develop technologies that will allow us to measure simply at a low cost the deformity of bridges-the fatigue and pain of bridges, so to speak-using measuring equipment and knowledge of mechanics. In particular, technologies that will allow us to see and examine the unseen are essential. Infrastructure as a whole, and not only bridges, becomes exposed to the risk of damage and accidents while we remain unaware. It's already too late once damage or an accident occurs. Unlike human beings, self-healing capabilities cannot be expected of damaged bridges and infrastructure. People are the only ones who can care for the health of bridges. The best thing we can do is to detect and repair minor damage at an early stage. Traffic being stopped by bridge accidents or bridge replacement work would cause quite a burden on the people of Japan. Nonetheless, there is not much interest in these issues within our society. We should act as fast as possible to inspect our infrastructure and do something about advancing deterioration. The only possible measure we can take is preventive maintenance before damage from deterioration and disrepair rears its head. In particular, the infrastructure that was constructed in the 1960s during Japan's period of strong economic growth is approaching an advanced age. It was during this time period that the construction of bridges peaked. During this period of mass production, economic efficiency was prioritized and as a result bridges were built using small amounts of materials, meaning that the structure of some bridges could be overly-light and long. It is for this reason that there are concerns of aging proceeding rapidly. As bridges age and become weaker, the risk of damage and accidents increases. Focused reinforcements are necessary for these overly-light and long bridges. The best thing that can be done to prolong the life of these bridges is to conduct adequate inspections and analysis and adopt effective countermeasures, fully utilizing the passion of engineers and cooperation of residents.

Photo 1: Bridge collapse in Minnesota (source: MN/DOT)

Photo 2: Deterioration of a bridge with age (photo by Teruhiko Yoda)

In order to conduct preventive maintenance, both budget and technical issues must be faced. If it is assumed that the budget will be low, much will have to be done to secure and improve technical capabilities. If the number of young people and engineers falls as our society ages, and our infrastructure deteriorates as it advances in age as well, the succession of technology will become difficult. Both bridges (see Figure 1) and males from Japan's baby-boomer generation are aging at the same pace. Two things that we need to think about are stressing the importance of maintaining and managing our infrastructure, and making good jobs available in the infrastructure sector. If there are no good jobs in this sector, it is not likely that there will be any engineers in the future to carry on these technologies. To prevent the deterioration of our infrastructure and prolong its life, I believe that it is important for the current generation of engineers to leave these important tasks up to the future generation of engineers.

Teruhiko Yoda
Professor, Faculty of Science and Engineering, Waseda University

March 1970: Graduated from the Civil Engineering Department, School of Science and Engineering, Waseda University
April 1977: Served as assistant on the School of Science and Engineering, Waseda University
April 1980: Served as full-time lecturer on the Civil Engineering Department, School of Science and Engineering, Waseda University
February 1981: Served as part-time lecturer at Chuo Denki Tsushin Gakuen, Nippon Telegraph and Telephone Public Corporation
April 1982: Served as assistant professor on the Civil Engineering Department, School of Science and Engineering, Waseda University
April 1987: Served as professor on the Civil Engineering Department, School of Science and Engineering, Waseda University
April 2003: Due to a change in the department name, became professor on the Civil and Environmental Engineering Department, School of Science and Engineering, Waseda University
April 2005: Served as part-time lecturer at Hiroshima University
September 2006 to present: Following a school reorganization, has served as professor at the School of Creative Science and Engineering, Faculty of Science and Engineering, Waseda University

Bridges are Dangerous [Hashi ga Abunai] (co-authored), Gyosei, October 2010
Structural Mechanics [Kozo Rikigaku] (co-authored), Shokokusha, July 1999
"Civil Engineering" [Doboku Kogaku], chapter 3 in A Comprehensive List of Steel Structural Technology: Design Standards [Kokozo Gijutsu Soran: Doboku hen], Gihodo Shuppan, May 1998
Civil Engineering Handbook: Book 7 Structural Mechanics [Doboku Kogaku Handobukku: Dai 7 hen Kozo Rikigaku] (co-authored), Japan Society of Civil Engineers, Gihodo Shuppan, November 1998

May 2005: Tanaka Prize (Division of Outstanding Research Publication), Japan Society of Civil Engineers
October 2006: Good Design Award (Domain: Product Design), Japan Institute of Design Promotion
June 2008: 2006 Best Paper Award, Advances in Structural Engineering
February 2010: Civil Engineering Design Prize, Japan Society of Civil Engineers
June 2012: 2012 KSSC-POSCO Award, KSSC

[Area of Specialization]
Structural engineering, bridge engineering, structural mechanics