Major Research 2B Research on Life Cycle Management of Infrastructures

Background and Objectives

The ports, airports and coastal infrastructures that have been in service for a long time are increasing, but financial resources and the number of engineers for facility maintenance are limited. As important port, airport, and coastal infrastructure functions should be maintained, the strategic maintenance, renewal, and other measures to maintain such functions are strongly required.
 

Therefore, we are trying to establish methods for structure design and material selection which are excellent in terms of maintenance, and will develop techniques and technologies regarding various countermeasures for maintenance phase.

Research Topics

Research and development comprises the following three subthemes:

Activities in FY 2018

We used long-term exposure facilities to study how to predict chloride-induced concrete deterioration, the electrolytic protection characteristics of steel bars in reinforced concrete, and the concentrated corrosion mechanism that affects steel materials. We also obtained data on the durability of various wood materials and reinforced concrete that utilized recycled frame materials.
 

We aimed to establish a method for predicting the deterioration of protective coating methods against corrosion. To achieve this goal, we conducted continuous experiments at Hazaki Observational Pier, including exposure tests on steel pipe piles to which anti-corrosion protective coating had been applied. We also conducted accelerated deterioration trials and exposure tests to further elucidate the deterioration mechanism of petrolatum coating methods.
 

We evaluated the durability of concrete, in which low-grade aggregate (coral aggregate) and seawater as mixing water had been used, and conducted exposure tests to develop a concrete-curing technique using seawater. We also evaluated the durability of highly corrosion-resistant reinforcing steel and surface coating materials through exposure testing.
 

We conducted a comparative evaluation of the aggregate gradation of airfield asphalt mixtures by indoor tests on their rutting resistance, moisture susceptibility, water permeability, and other characteristics, aiming to prolong the life of airfield asphalt pavement.
 

We studied the solidification of filling material in caisson-type outer walls as a preventive measure against local failure due to repeated collisions of wave-dissipating blocks, focusing on how such solidification work, strength of filling materials, and thickness of solidification would affect the load-bearing and impact-resistant capacities of those outer walls. In addition, we examined a method for monitoring the effects of repairs performed on prestressed concrete (PC) members that are prone to chloride-induced corrosion, in order to improve the repair techniques. We experimentally examined the feasibility of performing repairs by applying surface coating to protect expansion due to alkali-silica reaction and/or delayed ettringite formation, evaluated the effects of the method, and improved the existing model.
 

We organized points that must be considered while designing steel and concrete members for future maintenance purposes, and reflected some of them in revised technical standards. We also proposed a flow chart for determining use-conversion of existing caissons. In addition, we examined methods for inspecting and diagnosing PC hollow girders that utilize high-durability materials.

We conducted monitoring verification tests using an IoT-enabled inspection and diagnosis system and investigated optimal threshold values for the maintenance and management of sensors for checking the corrosion prevention effects of petrolatum lining method. We also examined what points should be monitored that would be useful for determining the usability of the superstructures of PC open-type wharves when major earthquakes occur. Also, the applicability of performing inspections using underwater drones was examined.
 

We introduced new operational support functions including a shooting-omission prevention function and an autonomous collisionavoidance function into the ROV for inspecting the superstructures of piers and then conducted on-site demonstration test.
 

To advance the process of formulating preventive and maintenance plans for port and harbor facilities, we performed case studies on model piled piers, while formulating renovation scenarios (selection of an optimal renovation method and timing) based on which those piled piers can be converted into a preventive maintenance, using LCC and NPV as evaluation indicators.