The Analysis Of Local Stress Of The Cable-girder Anchorage Zone

Cable-stayed bridge is a kind of bridge style of having lightness structure and large span capabilities, which develops very quickly and steady in the past several decades.The cable-girder anchorage zones of cable-stayed bridges, which bear giant cable forces and have complicated structure, are keys to structure design.lt is important to know the stress distribution of anchorage zones well.First, the development of cable-stayed bridge and the main structural types of the anchorage zones between the box beam and cables are described in this thesis, and then the analysis theory of cable-stayed bridge is introduced.A cable-stayed bridge in Danyang was taken as research background, the plan finite element model is established using the plane finite element software (Dr. bridge V3.20)and the static analysis of the bridge is carried out.The impact of stress and deformation at each construction stage and finished stage are considered under all kinds of construction loads.The whole bridge's stress and deformation characteristics are analyzed under the long-term combination,under the short-term combination and under the standard combination.On the basic of plane analysis, a steel box having the largest force was selected and the space finite element model of the cable-girder anchorage was established through the general finite element program-ANSYS.First the line elastic analysis for the anchor area was carried out, obtaining the following conclusions:overall stress of the anchor area is not large under the design load,the largerst stress appears in the anchor backing strip where contacts with the anchorage;the thickness change of the anchor backing strip and the power transmission board have affects greatly to their own stress and the stress of stiffening rib Nl,but have less affect to stress the web plate,roof stiffening rib and bottom stiffening rib.Next ultimate bearing capacity of cable-girder anchorage zone was calculated by nonlinear FE analysis.Under 3.48 times of design cable forces, the anchor area starts to yield and get to the plastic stage; Under 6.23 times of design cable forces, the anchor area yields completely; the tensile stress achieves the ultimate bearing strength and the deformation of the anchor area is also large. Through the space finite element analysis we can see:the rigidity and intensity of the anchor area satisfy the request, and the anchor area has the enough safety margins.