Can Sensors Solve the Deterioration Problems of Public Infrastructure?

Abstract

Various deteriorations are detected in public infrastructures, such as bridges, viaducts, piers and tunnels and caused fatal accidents in some cases. The possibility of the applications of health monitoring by using sensors is the issues of this lecture. The inspection and diagnosis are essential in the maintenance works which include appropriate rehabilitations and replacements. The introduction of monitoring system may improve accuracy and efficiency of inspection and diagnosis. This seems to be innovation of maintenance, old structures may change smart structures by the installation of nerve network and brain, specifically. Cost- benefit viewpoint is also important point, because of public infrastructures.The modes of deterioration are fatigue, corrosion, and delayed fracture in steel, and carbonization and alkali aggregate reaction in concrete. These are like adult disease in human bodies. The developments of Infrastructures in Japan were concentrated in the 1960th and 1970th. These ages are approaching 50 and deterioration due to aging has been progress gradually. The attacks of earthquakes are also a major issue. Actually, these infrastructures have been supporting economic and social activities in Japan and the deterioration of public infrastructure has become social problems. How to secure the same level of safety and security for all public infrastructures is the challenge we face now.The targets of monitoring are external disturbances such as traffic loads, earthquakes, winds, temperature, responses against external disturbances, and the changes of performances. In the monitoring of infrastructures, 3W1H(WHAT, WHERE, WHEN and HOW) are essential, that is what kind of data are necessary, where sensors place, when data are collected, and how to collect and process data. The required performances of sensors are accuracy, stability for long time. In the case of long term monitoring, the durability of systems needs more than five years, because the interval of regular bridge inspection works are five years. The supply of powers sometimes becomes serious problem. Some case studies will be presented here.