Toshiba Demonstrates Technology for Analyzing and Visualizing the Internal Soundness of Bridge Decks at the Fukuoka Expressway

TOKYO—Toshiba Corporation (TOKYO: 6502) has developed a technology that could analyze and visualize the internal soundness of bridge decks which cannot be seen from the exterior, and demonstrated its effectiveness for bridges at the Fukuoka-Kitakyushu Expressway Public Corporation (Fukuoka Expressway). This technology uses sensors installed at the undersurface of the deck to acquire and digitize data from weak waves generated at the road surface as vehicles cross the bridge, analyzes the data to digitize internal damage and visualize as a soundness map that cannot be recognized through conventional visual inspections. This technology will enable repair plan formulations and work task implementations according to the internal condition of bridges, and furthermore promote the digitalization of bridge aging countermeasures and contribute to more efficient bridge repair and extending the service life of social infrastructure.
Toshiba has demonstrated this technology for repairs to bridge decks at Fukuoka Expressway Route 2, confirming the validity of evaluations of the internal condition of bridges. The company will continue conducting demonstration with Fukuoka Expressway, and together with its operating company, Toshiba Plant Systems & Services Corporation, aims to start providing this service to road operators in FY2024. 

Infrastructure maintenance is becoming increasingly important for the long-term stable operation of social infrastructure. Especially in Japan, where many roads, bridges, tunnels, and other infrastructure that were built during the period of rapid economic growth are now 50 years old and rapidly deteriorating, while issues such as labor shortages due to an aging and shrinking working-age population are becoming apparent. In addition, there was an incident in 2012 in Japan, which an overhead ceiling panel in Yamanashi Prefecture’s Sasago Tunnel collapsed, triggering a revision of Japan’s Road Act, making it mandatory to inspect once every five years by direct visual inspections, and requesting for safe and efficient infrastructure maintenance.
Toshiba has recently engaged in the development of technologies that will contributes to more efficient bridge repair and extending the service life of bridges. Aging bridges undergo major renewals, including replacement, but many are repaired to extend their service life. When repairing concrete decks in bridges, the extent of deterioration is conventionally determined from exterior visual inspections, from which the scope of repairs and construction method must be decided. However, making these decisions from external appearances alone has been problematic. Other challenges include the difficulty of determining priorities for achieving well-rounded maintenance plans and confirming the effectiveness of the repairs themselves.
When performing repairs, it will be more appropriate if their scope and method can be determined in consideration of actual internal deterioration, and if a maintenance plan can be formulated based on priorities. In addition, means for monitoring the status of improvements to internal damage after repairs would eliminate the need for repeated repairs due to missed repairs and the like, thereby enables to achieve efficient infrastructure maintenance.

In response, Toshiba has developed a technology that uses weak waves generated on the road surface when vehicles cross the bridge to analyze and visualize the internal soundness of bridge decks, which cannot be seen externally. In this technology, multiple sensors are first installed at the undersurface of bridge decks, where they will not interfere with vehicle travel. These sensors measure waves (elastic waves) propagated from the road surface to the deck’s interior, allowing use of the company’s proprietary sensor data analysis technology to analyze the deck’s soundness. This method analyzes the source distribution of elastic waves propagating through the deck, along with the soundness according to the density of wave sources in the area of interest. Such analysis can be used to map soundness levels within the measurement area (Figure 1).
This technology is particularly suited for extracting target areas requiring concrete repair, and visualization of concrete repairs effects. By extracting target areas requiring concrete repairs, allows to identify areas in need for appropriate repairs. In addition, visualizing of concrete repairs effects, allows confirmation of their effectiveness after the repair, preventing missed repairs and other problems, which would lead to reduced future repair costs.
Toshiba has demonstrated the effectiveness of this technology by conducting measurements at concrete decks of Fukuoka Expressway Route 1 and Route 2 in August and October 2021 and January 2022 (Figure 2 and 3). In those demonstrations, 18 sensors were installed in an approximately 4m × 1m area, and data were acquired over approximately 2–6 hours during each demonstration period. Measurements taken before and after deck repairs allowed visualizations of restoration soundness through comparisons of soundness maps.
This technology enables the extraction of damage inside bridges that cannot be confirmed by conventional visual inspection and visualization of the extent of such damage, contributing to extending the service life of social infrastructure though efficient and appropriate infrastructure repairs.

Toshiba will continue to conduct demonstration with the Fukuoka Expressway, and together with Toshiba Plant Systems & Services Corporation aims to start providing this service to road operators in FY2024. This technology can be applied not only to bridges but also to a wide range of concrete structures, to expand the scope of application beyond bridges, Toshiba will continue to conduct demonstration on a variety of concrete structures. Using this technology, Toshiba will promote the digitalization of measures for aging infrastructure and contribute to realize circular economies.
This newly developed technology includes results from the “Robot and Sensor System Development Project for Infrastructure Maintenance and Disaster Surveys,” a research project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).