Case and interview
Creating customer-based solutions that have grown into technologies focused on and making use of on-site installations through demonstrative experiments
We were searching for technology we can use on site
The West Japan Railway Company has formulated the JR-West Group Railway Safety Think-and-Act Plan 2022. The plan contains a message that the group will work to improve the safety of railways with a sense of mission as a corporate group that contributes to society while having an awareness of its responsibility as a railway operator that has its passengers’ lives in its hands. I asked Hori, who is affiliated with the Structural Technology Department and is in charge of research and development, about new technologies relating to the safety and security of bridges and other railway infrastructure.
The risk of tendon rupture in prestressed concrete structures is an issue common to bridge managers
› Why did you decide to try using SenrigaN?
Some prestressed concrete structures manufactured in the 1970s are developing faults in the grout filling. The cause cannot be dismissed merely as faults in construction, and the background contains various elements, including the materials and construction methods used at the time the structures were built. If a structure has grout filling faults, this will eventually lead to corrosion of the tendons inside the prestressed concrete, which then risk rupturing. This can be considered to be common to prestressed concrete structures built around the same period, and it is not limited to prestressed concrete structures belonging to this company or to railways. The reality is that local governments and road companies that manage road bridges, as well as railway companies besides us, are also facing the same problem. As we investigate how to monitor the bridge where the SenrigaN demonstrative experiment was conducted, we have installed a system to detect tendon ruptures known as external cable tension monitoring as experimental works. Amid the risk of tendon ruptures, it was mentioned that the SenrigaN technology that Konica Minolta introduced to us could be used in detecting tendon ruptures, so we decided to conduct a demonstrative experiment on an actual bridge.
› What was your evaluation of SenrigaN after using it?
To begin with, it is a device that can be used on site. Next, it is easily portable and enables immediate confirmation of the measurement results in real time. These are the points that we regarded highly, because the phenomenon of rupturing requires a quick response, and therefore needs immediate decisions on site. Moreover, I got the sense that it was very easy to use, such as being able to upload the measurement results to the cloud for immediate data sharing. We also had the magnetic sensors improved so that they would not be affected by magnetic fluctuations caused by the electricity used to run the trains. Through Konica Minolta’s ongoing development of and improvement of the instruments in SenrigaN, I got a true sense through the demonstrative experiment that rupture detection has reached a level that can be realized in the field. Conversely, my honest impression is that we need to seriously consider how to make use of the SenrigaN technology on site and how this should be applied in the process of bridges deteriorating.
› Have you considered any other means?
First, for insufficient grout filling, we perform drilling surveys. If we discover faults in the grout filling through a drilling survey, we refill the grout. During drilling surveys, we can directly observe the internal conditions using a fiberscope, and by this method, we check the state of tendon deterioration. We have not had any cases where we found ruptures by visual inspections after drilling, so to be honest, we felt that there was not much need on site to go as far as rushing to do tendon rupture tests. However, I am sure that the risk of tendon rupture will come to the forefront sooner or later. As a department that considers how we should conduct maintenance in future and performs research and development with an awareness of the people on site, the technology to detect tendon ruptures in prestressed concrete is important for the load-bearing capacity of bridges and is a technology that we must develop.
We did not get to the point of demonstrative experiments of rupture detection using the preexisting flux leakage method, but we had the opportunity to learn about Konica Minolta’s technology while looking for and considering a range of inspection technologies, and as we heard an explanation about it, we talked about trying it out this time.
› What is your process for adopting new technologies?
There was a period when we mainly considered introducing technologies from manufacturers that we had developed relationships with. When we decided on this demonstrative experiment using SenrigaN, it was before the COVID-19 pandemic, at a time when JR West Japan was growing more motivated to make an attempt at open innovation. It was also significant that there was a shift towards eagerly making use of new technologies if there was something that looked like it would fulfil our testing needs. Konica Minolta is not a company with particularly lengthy experience in the infrastructure maintenance field, but we did not take that into account, and it was as though Konica Minolta got in touch just as we were looking for technology we might be able to use.
› What is necessary when adopting new technologies?
Even when it works well in experiment in the laboratory, some issue that does not go well out in the field always pops up. No matter what the process leads to our encounter with the technology, we make sure to gather information with a strong awareness that we have to try it out in the field.
› How would you like to use non-destructive testing in the future?
In non-destructive testing technologies, we have tried using the SenrigaN technology for testing on prestressed concrete structures, but our structures also include many that are built with ordinary reinforced concrete. Like prestressed concrete structures, many reinforced concrete structures were built during the postwar high economic growth period, so faults are occurring in reinforced concrete structures as well. The current reality is that there is much cracking and peeling caused by rebar corrosion. In that sense, the technology we want as the people who maintain these is non-destructive technology to detect rebar corrosion.