Akashi-Kaiko Bridge
漂的读音1. Physical Conditions
The Akashi Strait, which connects Osaka and Harimanada, is about 4km wide. The gment spanned by the bridge has a maximum depth of 110meters and a maximum current speed of 4.5m/s. The Strait has been a productive fishing area since ancient times, and is important waterway, ud by over 1400 vesls a day. To ensure the safety of marine traffic, an international water-way 1500m wide has been t by the marine traffic safety law.
凉拌洋葱的做法Several vere conditions were encountered, such as strong currents, deep water in which divers were unable to explore the abed. It was also necessary to prerve the fishing area and to ensure the safety of marine traffic. Tho difficulties were conquered through investigations and technical examinations.
2. 鲜人参鸡汤Basic Design Conditions
The basic design conditions of the Akashi-Kaiko Bridge are summarized as follows:华润超市
比例尺的计算公式1. The width of the straits is about 4km, and its depth along the propod bridge route reaches about 110m.
铃声排行榜2. The natural conditions at the main pier site: water depth=45m, maximum tidal current=4.0m/s and maximum wave height=9.4m.
3. The wind condition: basic wind speed for design(defined as 10 minutes speed at 10m above the water level with the return period of 150 years)=46m/s and reference wind speed against flutter=78m/s.
4. The geological condition: the basic rock beneath the straits is granite, on which Kobe Formation (alternating layers of sand stone and mud-stone in the Miocene), Akashi-Formation(mi-consolidated sand and gravel layer in the late Pliocene and the early Pleistocene) and the Alluvium layer are deposited.
5. The design earthquake: the one which occurs off the Pacific coast about 150km away
with the magnitude of 8.5or the ones which are expected within radius of 300 km with the return period of 150 years, and
6. The social conditions: a waterway within 1500m in width and for heavy a traffic is designed amid the straits, and lands on both shores are highly utilized. The bridge is for 6-lane highway with the design speed of 100km/h.
3. Basic Design Conditions
The Akashi-Kaiko Bridge, therefore, has the following characteristics on design and construction. However, its design is strongly influenced by the construction method, becau design of a huge structure cannot but be done without consideration of the construction method and procedures.
1. In theory, the minimum clear span length may be slightly longer than 1500m, which is the width of the waterway, but it is better for the main piers to keep off the waterway with some margin to spare, even during construction to ensure the safety of maritime traffic, a
s is required by law. Accordingly, veral comparative designs were developed for various main span lengths around 20000m, and the conclusion was that the span length from 1950m to 2050m yielded the minimum construction cost. The position of two main piers was finally decided from the topographical and geological conditions after curing the width of the waterway and its side margins, which fact leads to the main span length of 1990m(final length of 1991m was due to the Kobe earthquake).
2. The two main piers were decided to be direct foundations having circular plane shape, and “Laying-down caisson method” was lected for their construction, with which HSBA had been familiar since the construction of Seto-Ohashi Bridge in 1980’s. However, its excavation method and underwater concreting method were improved from previous ones due to various technical developments done after then. The caisson had a possibility to overturn from scouring due to the accelerated flow and hor shoe vortexes both of which were generated by the prence of the caisson itlf unless some countermeasures were taken, becau the Akashi Strait had its a bottom covered with sand and gravel and its tidal current was rapid. Accordingly, protection against the scouri
ng with filter units and cobble stones laid on them were placed.
君子有三畏
3. The side span length was determined to be 960m so that both anchorage might be located near the original shore lines where obtaining working yard by reclamation was rather easy. The body of two anchorages was designed to be a conventional gravity type. Becau the anchorages body is a huge RC structure to which many people can make easy access, its shape is designed so as to lesn an oppressive feeling, and precast panels were ud as remaining form which had a superior external appearance and pattern to avoid monotony of the concrete surfaces. The panels precast in a factory can also rai durability of the mass concrete cast in-site. On the other hand, two foundations were quite different by reflecting difference of the geological conditions. Especially, 1A(Kobe side anchorage) foundation became the world’s largest foundation for a bridge with the diameter of 85m and the bottom depth of 61m.关于长城
