ABSTRACT
The Honshu-Shikoku Bridge Expressway Company is responsible for the maintenance of 17 long span bridges composing three main highways between Honshu and Shikoku islands in Japan. Superstructures of these long span bridges are mainly made of steel. Inspection and maintenance on welding, bolt connections and painting are necessary. Access to all elements and components of long span bridges within arms-length distance is inevitable for inspection and maintenance works. However, access to all elements and components is not an easy task because these bridges cross over the sea and maximum elevations of the main towers are more than 200m above the sea level. Due to high elevations, it is required to ensure safety and efficiency for inspection and maintenance works. It is not realistic to install scaffoldings whenever inspection and maintenance works are performed. Because of these circumstances, an easy access method to all elements and components of long span bridges had been investigated from the beginning of the construction of the Honshu Shikoku Bridges. Based on the investigations, permanent gantries were developed and designed for superstructures. There are four kinds of gantries including a suspended gantry, an internal gantry, a tower gantry and a cable gantry. Total of 152 gantries are installed on the Honshu Shikoku Bridges. Among the gantries, the tower and cable gantries can be removed and installed. This paper presents improvement and renovation of gantries as well as the efforts to increase access areas to the Honshu Shikoku Bridges.
