Public Works Research Institute

Research on Renewal and newly construction of Infrastructure for Lifetime extension and Efficient Maintenance

Japan's social capital stock was mainly built in the period of high economic growth, which raises the concern about a rapid increase in the number of aged stocks. It is essential that these cases be renewed without interrupting the related services. In order to steadily renew and build a new social infrastructure under harsh financial conditions, it is indispensable to have a system that is precisely aligned with the level of importance of each structure.

The road structures that compose the most vital routes of the country, for example, need to have high durability and a low life-cycle cost and maintenance workload. On the other hand, there are smaller structures that, despite not being demanding in terms of management, exist in vast numbers. For these cases, it is advantageous to build a structure that allows to identify which parts require renewal, as well as when they require it, with a simple inspection. Therefore, this research aims to develop the material and evaluation method required to implement new technologies that suit the social needs as in the case above.

Methods to Improve the Quality and Reliability of New Bridges

Verification of applicability of dynamic loading test of single pile

Rapid loading test (with an actual pile) being conducted Rapid loading test (with an actual pile) being conducted

We compared the results of ultimate bearing capacity measured by rapid loading test, one of the dynamic loading tests, with the one measured by static loading test currently set as the standard. The result of comparison shows the one measured by rapid loading test is on the same level with the one measured by static loading test, and revealed that the rapid loading test is applicable to the bearing capacity evaluation at the pile head. Thus, we contributed to the rationalization and improvement of the reliability which bearing capacity of piles is evaluated under complex soil conditions or when applying a new construction method.

Analysis of Reliability Improvement in the detail category for expressing Fatigue Strength


Calculated with the conditions of “Current of 260 A or less” and “gusset length of 100 mm or less” To improve the reliability of the design and evaluation method of fatigue durability of steel bridges, we analyzed the factors that influence the fatigue strength of welded joints using the multivariate analysis method and suggested which test conditions should be recorded as the fatigue test data to be used as the basis of fatigue strength setting.

Development of a durability design method that reflects the difference in reliability of quality

Coring analysis is performed regularly in collaboration with the road administrators Coring analysis is performed regularly in collaboration with the road administrators

To clarify the deterioration mechanism of a bridge in a severe salt damage environment, we obtained the initial physical property values of the concrete of the pier of Irabu Bridge when it was built to conduct a long-term state observation.