Construction technology

Substructure

Scour protection

Development of scoue protection countermeasures to protect huge substructures under strong tide from overturning

At the Akashi-Kaikyo Bridge, the seafloor around the substructure is scoured by strong current, and will be overturned if nothing is done to prevent it.

We confirmed the scouring conditions over many years by means of numerous hydraulic experiments conducted both in the laboratory and on-site, and countermeasures were developed taking into account reliability and the workability in a short time.

Foundation format

Development of safe and reliable substructure construction method in deep water with strong tides

The key to constructing the Honshu-Shikoku Bridges was to overcome the deep water and strong tides of their environment.

Therefore, through various field experiments, and development of and experiments of construction machinery over many years, we have developed the laying-down caisson method and multi-column foundation construction methods, which have different concepts from the previous concept based on land construction.

In order to realize these substructure construction methods, we further developed underwater blasting method, seafloor excavation method in strong tides using clamshell dredger ships.

Superstructure

Cables

Development of a construction method for suspension bridge cables to shorten construction time required and to improve quality

In the construction of the long-span bridges of the world, the aerial spinning erection method, in which wires are drawn out and erect one by one, has been generally used for cable erection.

For most of the suspension bridges of the Honshu-Shikoku Bridges, after conducting workability tests and investigations at the actual bridge, we had adopted a prefabricated strand erection method that had good workability and quality even under strong winds, and was able to shorten the erection time.

While preparing for the lengthening of bridges, we have pursued economic efficiency while improving quality and shortening of erection time.

Vibration control system

Development of a vibration control system for towers and girders which are unshaken by the wind

Since long and large-scale structures are narrow, tall and unstable in the erection situation, they are shakend even in a slight wind. And their erection workability get worse and their quality is damaged. Therefore, we clarified vibration phenomena by conducting wind tunnel tests and analysis for towers and girders, and developed rational and economical vibration control devices and vibration control methods taking into consideration the characteristics of the structures.

Girder erection

Development of an automatic position control system for barges that enable block erection work in strong tides

The block erection method is one of the best erection methods to erect the stiffening girders of a suspension bridge safely, reliably, economically, and in a short time, but it was necessary to maintain positon of the barges in strong currents.

Therefore, we developed an automatic position control system for self-propelling barges in which it is possible for the barges to maintain a fixed position even in tidal currents using a position measurement system.

As the result, block erection work became possible even in tidal currents, and stiffening girders could be erected safely and reliably in a short period of time.