Design on Anchorage Foundation of Suspension Bridge

Dec. 28,2018
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As the best spanning bridge type at present, suspension bridge has been widely used in the 20th century. For example, the Akashi Kaikyo Bridge which span up to 1 991 m in Japan and the Messina Strait Bridge which span up to 3 300 m have been successfully built, and the program of super-span suspension bridge of Gibraltar with a span of 5 000 m is also officially proposed. From above, the feasibility of the underground foundation type will be the most critical factor affecting the feasibility of the overall scheme. Gravity anchorage is widely used because of its superior geological adaptability, and large sinking caisson is the main gravity anchorage traditionally.

The advantage of traditional caisson is that the bearing capacity is large and the displacement is small, and the limiting factor of large caisson application is the most unfavorable conditions beyond the operational phase during the caisson sinking process, resulting in security risks in the process of sinking.

Design and Model Test on Split-combined Caisson Anchorage Foundation of Suspension Bridge published on China Journal of Highway and Transport by MU Bao-gang et al., proposed a split-combined caisson to decrease the difficulty of sinking without reducing the bearing capacity of caisson.

simulation experiments and preliminary analysis were carried out to the conclusions:

(1) according to the concept of “Whole into Parts”, the separation distance and burial depth of anchorage foundation of split-combined caisson can be adjusted by mechanical characteristic. split-combined caisson may be a foundation form to replace traditional caisson anchorage with huge size under the premise of ensuring reliable bearing capacity. This foundation can also reduce construction difficulty, and provide a new way to eliminate the potential safety hazard of traditional large caisson appearing in the sinking phase.

(2) Comparing the mechanical behavior of split caisson with the traditional one under same horizontal load, the results showed that the former with the same construction materials and same volume had the better horizontal bearing capacity than the latter.

(3) The distribution characteristics of the soil pressure for the two caissons of the split caisson were analogous. The front caisson undertook more horizontal load than the back caisson under long-term horizontal load, and the sharing proportion of front caisson was about 65% in this test.

(4) Under the test conditions and long-term load, the distribution of the soil pressure reached to stability before the deformation of caisson, and the degree of participation of the soil in front of the caisson attenuated with the distance from the caisson.

(5) The conclusion above is only a preliminary verification of the load distribution and deformation characteristics of split caisson, and the influences of factors such as caisson depth and rigid caps on practical application need further research.

Corresponding Author: MU Bao-gang
CNKI Press Officer: ZHONG Ming

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