Mechanical Analysis Of Caisson Anchorage Of Suspension Bridge Under The Main Cable Force

With the rapid development of transportation business in our country, more and more large span suspension bridges are built. Anchorage is one of the key structure of suspension bridges,its reasonable force in relation with the safety of suspension bridge during construction and operation.Main cable as a link between the top structure and bottom structure of suspension bridge,the function of its tensile force directly affects the stress of anchorage and the displacement of soil around the anchorage. Main cable tension of Suspension bridge is transferred to the foundation soil through the anchorage system,making the stress of anchorage and the foundation soil change, and the bearing capacity of anchor and adjacent soil affects the safety of the entire suspension.This paper is based on the north anchorage engineering of Wuhan Parrot Cay Yangtze River Bridge. The mechanical properties of anchorage before and after the function of main cable force is analyzed by the finite element software ADINA. At the same time, the working properties of the anchorage caisson foundation in variety loading conditions are analyzed systematically,and the ultimate bearing capacity of open caisson anchorage is discussed.The results show that:(1) Caisson under its own weight overall by the eccentric loads, partial center of gravity, resulting in dumping after the caisson.Open caisson and the circular diaphragm wall before and after the two side have the high tensile stress.Therefore, the post-pouring is set in saddle and ballast to avoid the high stress in the the anchor body.The tensile stress concentration region is distributed mainly over the the bottom of the cross wall,the junction of the cross wall and the sidewall of open caisson.The high tensile stress region is distributed mainly over the side walls,the junction of the side walls and buttress,the back-end cantilever portion of the ballast.So can strengthen the reinforcement of the cross-wall and the back-end cantilever portion of the ballast during construction.The maximum vertical displacement of the anchor appears at the top of the caisson rear side.The vertical displacement and horizontal displacement of anchorage and the settlement of adjacent soil values are within specification allows.(2) After applying the main cable tension, the main cable force balance the eccentric load on the anchor,leading to the tensile stress concentration area of the wall is also reduced. The principal stress of the foundation is mainly in a low voltage stress state,And the local tensile stress appears in front and rear side of the anchor.The maximum tensile stress appears in the intersection of the front side of caisson and the top of soil.Open caisson anchorage changes from backward to forward, rigid body rotation occurs.The maximum displacement of the anchor occurs in the intersection of the front and rear side of the caisson and the top of soil.The soil near the front side of caisson anchorage settled,the back side swelled.The maximum vertical displacement and the maximum horizontal displacement in the front and rear side of the soil near the caisson anchor occurs in the intersection of the top of soil and the front and rear side of the caisson.The maximum horizontal displacement of the anchor body theory splay points is controlled in the range of engineering requirements.(3) Multiply the main cable under tension, the main reason for the caisson anchorage reached ultimate bearing state is the soil in the front-end of anchorage reached ultimate bearing capacity. In order to ensure the safety of similar bridge engineering,the ultimate bearing capacity of the soil on the front of anchorage should be analyzed deeply.