Nonlinear Analysis And Experimental Study Of Self-anchored Suspension Bridge

Self-anchored suspension bridges are increasingly appreciated by engineers for their aesthetic look, low cost and high adaptability. Many self-anchored suspension bridges have been completed or are in construction in the world. No matter for.construction or mechanical properties, self-anchored suspension bridges differ from conventional suspension bridge and have their own particularity. Combined with the engineering practice, this paper gives the study and discussion about mechanical properties, limit span, ultimate bearing-capacity and construction control of self-anchored suspension bridge. The main research work covers the following aspects:(1) Based on the finite displacement theory and considering mechanical properties of self-anchored suspension bridge, the nonlinear factors, including sag of main cable, large displacement, initial internal force, concrete shrinkage and creep and loss of prestress, are fully considered, and the finite element method suitable for nonlinear analysis of self-anchored suspension bridges is presented in this paper. Through detailed analysis of a self-anchored concrete suspension bridge with span of 240m by using the finite displacement theory, it is found that a self-anchored suspension bridge with span 200m approximately meets the elasticity theory and the nonlinear behavior can be ignored. When greater the ratio of rise to span of main cable is adopted, the structural rigidity becomes greater and the internal force caused by live load becomes smaller. The concrete shrinkage and creep of stiffening girder has great influence on the internal force and deformation of the structure. Deformation of main girder due to compression and concrete shrinkage and creep has a significant influence on the configuration of main cable at the stage of construction. So it should be fully considered in design of the configuration of main cable.(2) The limit spans of the common twin-tower three-span self-anchored suspension bridges and single-tower two-span self-anchored suspension bridges are deduced. Some factors, such as ratio of rise to span X of main cable, ratio of side-span to mid-span β. ratio of tower height to main span μ, second dead load and live load, are analyzed in this paper. The limit span of the self-anchored suspension bridges with concrete stiffening girder and with steel stiffening girder, are discussed in detail, and the respective limit spans are given. The result shows that the following measures can increase limit span of a self-anchored suspension bridge: a larger ratio of rise to span is adopted for the main cable of mid-span; the main cable and the stiffening girder are made of high strength and light weight materials; and the second dead load is reduced as much as possible.(3) In order to analyze the ultimate bearing capacity of self-anchored suspension bridges, the reduced stiffness method for 2D beam element considering the nonlinearity of material is given, and the finite element model of double-layer beam for nonlinear analysis of steel-concrete composite beams considering nonlinear effect of slip is created. Then, through analysis of ultimate bearing capacity of three actual self-anchored suspension bridges, it is found that for the condition of loading on the entire bridge, the safety coefficients of ultimate bearing capacity of these three bridges are respectively 3.00, 2.88, 3.30. Breakage of these three suspension bridges is related to yield of hanger or main cable. Therefore, attention should be paid to selection of the safety coefficient in design of hanger and main cable. A smaller ratio ofside-span and mid-span leads to too small reaction of the anchor, and causes much reduction of the ultimate bearing capacity. The further study shows that upon break of the bridge, the result based on elastoplasticity and that based on elasticity, no matter for deformation or for internal force, are greatly different, showing that the structure comes to the elastoplasticity stage with a significant redistribution of internal force. The elastic ultima...