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Honshu–Shikoku Bridge Project Construction Technology
Survey Design

Survey Design

Survey of natural conditions

Tide current survey

Development of a three-dimensional distribution observation system for strong currents

In order to measure strong current, we have put to practical use an observation system based on field experiments and so on. The system was combination of a current velocity gauge which was able to collect three-dimensional, wide-area current velocity information using sound waves, and a ship position measurement system using satellites.

The information obtained by this observation has been useful for the planning of safe and reliable construction equipment and methods.

Geological survey

Building a technology for collecting undisturbed samples with a large size in deep waters and strong tides

An accurate understanding of the seabed is indispensable for safe and reasonable desig for underwater foundations.

Therefore, we were successful in collecting undisturbed samples of the seabed of the Akashi Strait, through the combination of the development of offshore platforms and casing fixing technique that allow offshore boring in deep water and in strong tides, and newly-developed large-diameter core sampling technology.

As a result, we were able to design the tower foundations with shallow supporting ground, because the ground which had been previously thought to be weak, are confirmed to be unexpectedly strong.

Substructure design

Earthquake-proof design

Formulation of earthquake-resistant design standards applied to the large substructure work of long-span bridges

Because of the large size of substructures, various research and experiments had been conducted for earthquake motion and design methods, we formulated an earthquake-resistant design standard based on a new concept considering the opinions of professional experts.

For the Akashi-Kaikyo Bridge, we developed earthquake-resistant design methods that take into consideration vibration of the further large sized substructures and the unconsolidated ground. And it was realized to design long-span bridge substructures reasonablly and economically.

As a result, even in the Great Hanshin Earthquake of January 1995, which caused damage to structures such as many buildings and bridges, there was no damage to the bridge itself.

Bedrock evaluation

Prior to the beginning of construction of the Honshu-Shikoku Bridges, there was not yet an established method of surveying and evaluating soft rock supporting the huge substructures of long-span bridges. For the construction of the Honshu-Shikoku Bridges, we had established a method of investigating and evaluating soft rocks and a substructure design method based on knowledge gained from various experiments and surveys, and as well as the opinions of porfesional experts. These methods enableed reasonable and economical design of large foundation structures and were also applied to the design of important structures such as nuclear power plants.

Superstructure design

Wind-resistant design

Formulation of wind-resistant design standard for long-span suspension bridges that take into consideration three-dimensionality, and that can withstand wind speeds of 80 meters per second

In Japan, which is prone to typhoons, bridges need to be safe against strong winds, so we have established wind resistance verification methods to ensure wind resistance safety by conducting numerous wind tunnel tests.

In addition, we have carried out long-term observations on natural wind and established wind resistance design standard in combination with the results of analysis of those observations. In addition to enabling wind-resistant design of long-span bridges, we have also developed various vibration prevention technologies.

In addition, we constructed a large wind tunnel test facility capable of performing wind tunnel tests with total bridge models of an overall length of 40 meters, enabling high precision wind resistance verification of suspension bridges of 2,000 meters in length, and economical design.

As a result, we confirmed that the Akashi-Kaikyo Bridge can withstand wind of 80 meters per second.

Structural design

Formulation of design standards to enable reasonable construction of long-span bridges

The technical standards (Specifications for Highway Bridges) that apply to bridges with a span length of 200 meters or less become unreasonable when applied to long-span bridges. For this reason, we have developed structural design standards such as load system, safety factor, and so on, to be used in the design of long-span bridges, based on developing testing and analysis methods, conducting surveys of traffic conditions, and so on.

By conducting experiments, we had also researched and developed a structural design method to cope with increasing span lengths of suspension bridges and cable-stayed bridges. These design standards are also used for designing long-span bridges in Japan and overseas.

Fatigue design

Formulation of Fatigue design method for high tensile steel susceptible to fatigue failure

High-tensile steel is indispensable for weight reduction of long-span bridges, but its disadvantage is its susceptibility to fatigue failure.

In order to solve this problem, we made a large-size fatigue testing machine, repeatedly conducted experiments and research, consulted the opinions of experts, and formulated criteria for fatigue design of structures using high tensile steel, and thereby established the foundation for this field.

Development of a composite structure of steel and PC girders

Promotion of longer cable-stayed bridges through using rationality of the right material in the right place

It is possible to make cable-stayed bridges with a short side span and a stable center span by using heavy and firm concrete girders for the side spans and light steel girders for the center spans, but in the conections of steel and concrete, materials which differ greatly in rigidity, the smooth transmission of stress is extremely important for the structure and for strength, and moreover it was a difficult problem.

Therefore, for the conection structures of steel and concrete, we conducted structural investigations including a destructive test of a full-scale model, developed a method for conection structure design, and applied to Ikuchi Bridge and one of the world's largest cable-stayed bridge, Tatara Bridge.