Akashi Kaikyo Bridge Research Articles

A fault model of the 1995 Kobe earthquake derived from the GPS data on the Akashi Kaikyo Bridge and other datasets

Co-seismic horizontal displacements, which have been obtained from recently released GPS observations on the Akashi Kaikyo Bridge, are examined for their consistency with displacements observed in the vicinity of the bridge. An E18.7°S displacement of 25.0 cm should be removed from them. The adjusted data indicate an additional fault segment beneath Akashi Strait. We construct a new fault model by adding this segment to a model assumed previously. We then recover the slip distribution over the new model by inverting these data together with other geodetic observations. The displacements calculated from the recovered distribution fit the observations well, and the distribution of slip indicates that the additional segment is closely related to the southern main segment of the previous model. Joint inversion of the geodetic and waveform datasets suggests large slips with longer duration in the shallow parts of these segments.

Multi-mode flutter and buffeting analysis of the Akashi-Kaikyo bridge

Flutter and buffeting are both issues of utmost concern in the wind-resistant design of long-span bridges. These aeroelastic phenomena are usually investigated by wind tunnel testing and/or an analytical approach. Since multi-mode behaviors have been reported with increased center-span length of bridges, considering the coupling effect among modes is necessary; and therefore, wind-tunnel testing with an aeroelastic full-model or a multi-mode analysis method is desirable. The Akashi-Kaikyo bridge, which is the world's longest suspension bridge with a center span of 1990 m, was opened in April 1998. Since the bridge is very susceptible statically as well as aerodynamically to wind due to its flexibility, wind-resistant design of the bridge was a crucial issue in the design process. For example, the bridge deflects laterally by about 30 m accompanied by large deck rotation of about −3° at the design wind speed. This requires true three-dimensional consideration in evaluating the bridge stability under wind. Wind tunnel testing was performed in Japan using a 1/100-scaled aeroelastic full-model of the bridge. In this paper, the flutter and buffeting responses of the Akashi-Kaikyo bridge are analyzed. The analytical method used here was a multi-mode analysis in the frequency domain in which mode responses obtained by a spectral analysis were summed including consideration of full aeroelastic and aerodynamic coupling among modes. The analytical results were compared with the wind tunnel test data. Comparison showed that there was good agreement between the multi-mode flutter analysis and the measurement, and that there was indeed a significant coupling among modes. Multi-mode buffeting analysis showed excellent agreement between the analysis and measurements in vertical and torsional response. However, the analysis over estimated lateral response. Significant coupling among modes was also observed in the buffeting analysis, and the multi-mode analysis predicted the measurements better than an equivalent single-mode analysis method.

The Tsukuhara Extradosed Bridge near Kobe

The concept of “extradosed” bridges, where the stay cables are functionally similar to external post-tensioning cables, was introduced by Jacques Mathivat in 1998. The Tsukuhara Bridge, part of a road network with the Akashi-Kaikyo Bridge, is the second application of this technique by the Japan Highway Public Corp. A decade ago, bridges with a 180 m center span were mostly cable-stayed or massive box-girder bridges, but the extradosed concept can be applied to such span lengths, resulting in lower construction costs. The extradosed design was also felt to fit better visually with a nearby cable-stayed pedestrian bridge.

CRUSTAL STRUCTURE BENEATH THE AKASHI KAIKYO BRIDGE AS REVEALED BY EXPLOSION SEISMIC EXPERIMENTS

A series of explosion seismic experiments were conducted along the 1995 Keihoku-Seidan Profile. Most of the records acquired at the foundations of the Akashi Kaikyo Bridge had very poor S/N ratios. However, the P-waves of the explosions could be successfully delected after enhancing the records. The P-wave velocity structure was subsequently derived by fitting the travel times. The shallow crustal structure beneath the bridge is composed of four layers, with P-wave velocities ranging from 5.2 to 6.0km/s. The structure derived here is an improvement to the shallow crustal structure revealed by previous explosion experiments done about thirty years ago.

明石海峡大橋道路灯器具の構造設計

明石海峡大橋道路灯器具の構造設計

Discussion on aeroelastic detail and control in the flutter occurrences of long-span bridges

Considering the trend of longer-span bridges in future, aerostatic and aerodynamic features play a major role in their design. In this paper, the interaction between aeroelastic forces and structural response is discussed along with the effects of structural countermeasures for flutter instability of suspension bridges with spans longer than the Akashi Kaikyo Bridge of main span 1990 m. This analysis is conducted using a newly developed direct FEM flutter analysis method and its assessment system. To gain its aerodynamic stability effectively, the mode-shape control concept is presented. Its effect is discussed quantitatively with examples as an interaction problem between aeroelastic force and structural response of longer-span bridges.

Study on offering points of traffic closure information for highway

In this Paper, appropriate place where traffic closure information is given to drivers in highways have been studied. Evasive maneuver of drivers and traffic volume have been considered as key parameters in this study. Effects of detour has been evaluated by using the relation between duration of traffic closure and prolonged travel-time. Moreover, a case study on traffic closure of the highway on Akashi Kaikyo Bridge have been conducted. It was concluded that the order of priority of massage boards on giving traffic closure information could be obtained by considering the effects of detour evaluated in this study.

An Analysis of Factors Affecting Choice Behavior of Akashi Kaikyo Bridge by Truck Transportation

An Analysis of Factors Affecting Choice Behavior of Akashi Kaikyo Bridge by Truck Transportation

Aesthetic Design for Akashi Kaikyo Bridge

The Akashi Kaikyo Bridge, part of the Honshu-Shikoku bridge project, is a suspension bridge with a center span of 1990 m. When completed in the spring of 1998, it will be the longest suspension bridge in the world. The bridge is expected to be an attractive addition to the highly urbanized area of Kobe. Therefore, the aesthetic design needed careful consideration. A suspension bridge consists of horizontal stiffening trusses, gently curving main cables, a pair of vertical towers, and anchorages. Aerodynamic stability is important in its structural design. For the Akashi Kaikyo Bridge, five types of towers were compared using 1:500 scale models. Given the fabrication and erection work for the structure, a basic truss-type design was chosen. Structural concerns dictated the shape of the stiffening trusses and the main cables. In the selection of color, the surrounding environment was studied. Further research using computer graphics and scale models and site appearance tests was carried out. Greenish-gray was finally chosen from among 30 candidate colors. To lessen the impact of the immense concrete anchorages, light and shadow effects were utilized, and vertical and horizontal indentation was adopted on the surface. The result will be structural beauty and optimum harmony of the bridge with its surroundings.

Effects on the Akashi Kaikyo Bridge

ABSTRACT The epicenter of the main shock of the 1995 Hyogoken-Nambu earthquake was very close to the construction site of the Akashi Kaikyo Bridge, which will be a three-span, two-hinge stiffening truss suspension bridge with a total length of 3,910 m upon completion. The bridge consists of tower foundations, anchorages, towers, cables and girder. At the time of the earthquake, the main cable installation had been completed and the working had reached the stage of cable squeezing. Immediately after the earthquake, a structural inspection, a survey of pier locations using an optical distance measuring instruments and a global positioning system and a geotechnical investigation were conducted. The basic information and technical data related to the earthquake and its impact including the displacements of the foundations on the Akashi Kaikyo Bridge are described in this paper.

Aesthetic Design for Akashi Kaikyo Bridge

The Akashi Kaikyo Bridge, part of the Honshu-Shikoku bridge project, is a suspension bridge with a center span of 1990 m. When completed in the spring of 1998, it will be the longest suspension bridge in the world. The bridge is expected to be an attractive addition to the highly urbanized area of Kobe. Therefore, the aesthetic design needed careful consideration. A suspension bridge consists of horizontal stiffening trusses, gently curving main cables, a pair of vertical towers, and anchorages. Aerodynamic stability is important in its structural design. For the Akashi Kaikyo Bridge, five types of towers were compared using 1:500 scale models. Given the fabrication and erection work for the structure, a basic truss-type design was chosen. Structural concerns dictated the shape of the stiffening trusses and the main cables. In the selection of color, the surrounding environment was studied. Further research using computer graphics and scale models and site appearance tests was carried out. Greenish-gray was finally chosen from among 30 candidate colors. To lessen the impact of the immense concrete anchorages, light and shadow effects were utilized, and vertical and horizontal indentation was adopted on the surface. The result will be structural beauty and optimum harmony of the bridge with its surroundings.

Wind Tunnel Test of the Akashi Kaikyo Bridge using Full Bridge Model

The Akashi Kaikyo Bridge is a suspension bridge under construction whose center span is 1, 990m. The bridge will be the longest suspension bridge in the world. Since the bridge is much longer than the present longest bridge, the aerodynamic characteristics of the bridge was evaluated through wind tunnel test using full bridge model as well as section model. This report outlines a study concerning the wind tunnel study using full bridge model in smooth flow and turbulent flow. The characteristics of flutter and gust responses observed in the wind tunnel test were shown and discussed.

Noise and Vibration Propagation Mechanism in Long Steel Ropes Using Two-Vibration Measuring Techniques.

A strange noise occurs around the anchor of the bridge when catwalk ropes of the Akashi Kaikyo Bridge collide with each other in a strong wind. This noise was studied using the two-vibration measuring techniques. The transfer function of vibrations, spacing δ on the rope, was measured. Peak and dip frequencies of the transfer function indicate that bending waves propagate in the catwalk rope. Since the propagation speed of the bending wave varies according to frequency, higher-frequency waves travel faster than lower-frequency waves. In addition, the acoustic radiation coefficient of the rope is less efficient in the low-frequency range. Therefore, the high-frequency range is emphasised. This is the mechanism of noise generation.

Effect of the Southern Hyogo Earthquake on the Akashi-Kaikyo Bridge

The Southern Hyogo Earthquake that struck near Kobe, Japan at 5:46 in the morning of January 17, 1995, had a magnitude of 7.2 on the Richter scale. The epicenter of the earthquake was very close to the construction site of the Akashi-Kaikyo Bridge, a long span bridge with center span length of 1,990 m. The earthquake caused considerable damage in Kobe and vicinity. When the earthquake occurred, the erection of the towers of the Akashi-Kaikyo Bridge, which are about 300 m tall, was completed, all the cable strands were placed and cable squeezing work was in progress. This paper outlines the earthquake and its effect on the bridge as determined by the first phase of investigation. A more detailed investigation is in progress.

Wind resistant design for long span suspension bridges

Considering the trend of longer bridges in the future, aerodynamic instability plays a major role in their design. In this paper, the aerodynamic characteristics and the efficiency of the structural countermeasures for aerodynamic instability of long span suspension bridges are discussed using the newly developed direct flutter analysis method for longer spans than the Akashi Kaikyo Bridge (main span 1990 m). For suspension bridges longer than the 2000 m-class the aerodynamic characteristics become worse as shown by the drop in flutter wind speed and the coupled torsional—vertical flutter response. The efficiency of the structural countermeasures for long span suspension bridges decreases for spans longer than 2000 m. Finally, the mode-control countermeasure (strengthening of deck rigidity in some region) was proved to be efficient in gaining stability against flutter.

明石海峡大橋1Aアンカレイジにおける高流動コンクリートの施工と品質管理

明石海峡大橋1Aアンカレイジにおける高流動コンクリートの施工と品質管理

Anchorages and Towers of the Akashi-Kaikyo Bridge, Japan

When completed, the Akashi-Kaikyo Bridge will be the longest suspension bridge in the world. It is a 3-span truss-stiffened suspension bridge designed to carry a 6-lane highway. Its main span lengt...

Aerodynamics of wind effects on the Akashi Kaikyo Bridge

The Akashi Kaikyo Bridge, which will cross the Akashi Kaikyo Straits with a shore-to-shore distance of about 4 km, is a very long-span truss-stiffened suspension bridge for six road lanes with a main span of 1,990 m and two side spans of 960 m. Its extremely flexible features, caused by the span length never experienced, increase importance of careful detailed considerations on static as well as dynamic effects in the aerodynamics of the superstructure. The paper describes some design considerations of wind effects and the outlines of full aeroelastic bridge model wind tunnel tests, together with primary test results analyzed so far, which have been conducted in order to carry out final verification of the wind resistance safety of this bridge at an especially constructed boundary layer wind tunnel of 41 m width.

Construction of boundary layer wind tunnel for long-span bridges

In order to carry out final verification of the aeroelastic safety of the Akashi Kaikyo(strai) Bridge, which has a main span of 1,990 m and two side spans of 960 m and a truss stiffening girder, its full aeroelastic model wind tunnel tests were planned and are now in progress. A geometrical 1 100 scale model was selected and primary dimensions required for the test section of wind tunnel were determined as follows: width 41 m, height 4 m and length 30 m. This paper presents some discussions related to this large boundary layer wind tunnel facility and some new ideas of modeling for the bridge.

Circumstances of wind-resistant design examinations for very long suspension bridge

This paper is a follow-up to the Preliminary Considerations for Wind-Resistant Design Code for the Akashi Kaikyo Bridge, as presented at the 7th I. C. W. E. in 1987. It consists of a summary of the “Wind-Resistant Design Code of 1990 for the Akashi Kaikyo Bridge”, a recapitulation of the tentative plan presented in the preliminary considerations and the results of wind-tunnel tests on the stiffening truss girder and the main tower. This paper complements the report entitled “Construction of Boundary Layer Wind Tunnel for Long-Span Bridge” presented in this conference.