Keep Earth Co., Ltd.
Masahiko Uemura, President

The degree to which architectural constructions such as bridges and buildings have deteriorated cannot be measured from only their appearance, and merely leaving any deteriorated constructions alone could result in serious injury.

Keep Earth Co., Ltd., which is situated in Kokubunji City in Tokyo, has therefore been addressing this issue in ensuring the safety of constructions utilizing a new technology to judge their health and thus prevent any accidents from occurring.

Venture company at Waseda University

The company was first established as a venture company at Waseda University in 2002 in utilizing the results of research of Waseda University and the Railway Technical Research Institute (RTRI).

"In the past we determined any damage to bridges and buildings caused by deterioration and natural disasters that could not be determined through their appearance by listening to the sound resulting from hitting the subject construction with a hammer via the human ear. And then to enable more precise decisions to be made we installed a large vibration generating machine to actually shake the bridge or building and measured the natural frequency with a sensor."

President Masahiko Uemura, who assumed his post in 2006, explained to us the above.

However, the method wherein the human ear was utilized in making judgments included fluctuations that depended on the listener. It was also not very objective as the evidence used to make the judgments could not be quantified. Installation of the vibration generating machine however also required a lot of preparation and time for the measurements to be made.

A health inspection via an impact vibration test settled this issue.

Scene where the bridge health inspection of "NSIRB" is underway

A merit is the inspections don’t require the traffic to be stopped.

Focus on the natural frequency of a construction

The technology was developed by Akihiko Nishimura, the chief of the Aseismic Research Laboratory of RTRI (present vice president of JR Souken Engineering). The health inspections of bridges of "NSIRB" and that of constructions (buildings) of "NSIS" are part of a system that focuses on the natural frequency determined by the weight and strength of the construction and that analyzes data from vibrations resulting from use of a weight and a plastic hammer. It is quite simple but very precise: The results of the measurements are output as numerical values, thus providing the criteria to use and which is also useful in determining the priority of repairs.

"It takes one whole day for the inspections via the vibration generating machine but only five minutes for the impact vibration test and one and half hours for all the necessary work."

The necessary time has therefore been drastically shortened, while the cost is said to be a tenth. The obtained data can be immediately transferred to a PC and quickly analyzed if then sent on by e-mail.

Provision of know-how to the inspection company

About 20 member companies of the "Bridge Health Inspection Workshop" conduct health inspections utilizing the impact vibration test. Keep Earth Co., Ltd. is the secretariat of the workshop and also creates reports based on the data obtained by the inspection.

"We are a venture company and hence needed to suppress as many fixed costs as possible. We are therefore not involved in making inspections ourselves and instead leave that to external companies to whom we then provide technical know-how."

Health investigations on bridges currently quite popular but is also being used on buildings.

"The technology originated in some joint research with RTRI, and therefore any bridges on the Shinkansen line have already had their health tested. Bridges managed by the Japanese government and local governments are currently being tested, although not yet to an adequate degree."

The municipal governments of local governments often do not have an appropriate organization or a big enough budget to inspect the health of bridges. The conventional method that utilizes the human ear is still often being used, and can sometimes inhibit the utilization of the new technology.

"The health inspections with the impact vibration test are based on the concept of their natural frequency, unfamiliar in general designs, and it is true that such a level of high precision could be unnecessary. However, many constructions built during the era of high economic growth are near the end of their useful lifespan: I think getting a precise and objective grip on their health is thus essential."

And in fact the tests proved to enable a lot of dangerous situations to be avoided. For example, precisely judging the health of bridges when their base is underground or in water was rather difficult; however, in some cases the impact vibration test was capable of identifying that some bridge columns had been dug out by the water flow of the river.

Jetty where the new system "Mighty CF-SP" was used to protect the steel piles from rusting

PC measurement system used onsite

Extended application to the advertisement poles

In addition to bridges and buildings the company is now extending application of the test to various other constructions such as in a system that was developed to inspect the health of the poles used to support advertisements in family restaurants and convenience stores. All of them involve the underlying theme of an "appropriate evaluation".

"Nobody else is doing anything similar, so we have not placed a lot of emphasis on protecting our technology with patents. All the know-how used in everything from the inspections to the creation of reports is absolutely unique and no one can imitate it: It is more beneficial for each other to disseminate the technology through workshops to members than enclosing it."

The company name of "Keep Earth" originates in incorporating the meaning of national conservation and being eco-friendly. They are also now addressing some other approaches as well as the health investigation. They expect to develop and sell the material used in a the new system of "Mighty CF" that prevents steel from rusting and the "Koho Club" where designers will be able to search for various construction methods and materials on a website.

"We were barely able to lead our technology to commercialization when I first became the president. But recently I have come to feel that our business model is being highly evaluated. We want to provide the right knowledge on disaster prevention and construction safety at least as well as before."

Keep Earth Co., Ltd.

Structural aseismic design, nondestructive inspection, and repair consultations

〒185-0024
Pare Stage Nishikokubunji 203, 3-37-1, Izumi-cho, Kokubunji TOKYO JAPAN
TEL: +81-42-306-3613
FAX: +81-42-306-3614
Capital: JPY 16 million
Number of employees: 6
http://www.keep-earth.com 【Japanese】