Structural Behaviors And Design Of Partial Cable-Stayed Bridge

In recent years, a new type bridge appears between PC box-girder bridge and PC cable-stayed bridge and is accepted and applied in some countries. It is called extradosed exterior cable PC bridge by a French engineer - J. Malival who advances this new structural concept and structural type of bridge originally. In Japan, this new type bridge is generally entitled cable-stayed bridge. But in china, it is called partial cable-stayed bridge by Mr. Yan Guo min who is a famous expert in bridge engineering field. Due to its predominant structural behavior and favorable economic index, partial cable-stayed bridge has good application potential.Firstly, the development of this type bridge is presented. Then some characters and basic mechanical principle of partial cable-stayed bridge are introduced. On the base of design practice and finite element analysis of three-span partial cable-stayed bridge, Xiaoxihu Yellow River Bridge in LanZhou, some key points in design practice and structural details are recommend. Finally, this paper discusses the application of partial cable-stayed bridges in middle span and long span and educes several conclusions as below:1 On arranging bridge span, the radio of middle-span and side-span of partial cable-stayed bridge is close to continuous beam even more, but its main span is longer than continuous beam. When girder height in middle fulcrum is same, the span of partial cable-stayed bridge can be longer one times over than that of continuous beam.2 Depth-span radio of main beam of partial cable-stayed bridge is larger than that of cable-stayed bridge and is generally between continuous beam and cable-stayed bridge. Due to partial cable-stayed bridge's higher stifmess and letter deformation, it is especial for high standard railway bridge carrying heavy loads.3 Tower height is lower. It is generally only 1/12-1/8 of mainspan.4 Stayed cables are centralized relatively. They are generally disposed nearby middle of side-span and 1/3 middle-span. There has no anchorage cable at the end-girder of side-span.5 Stay cables are centralized together through saddle at top of the tower.6 The range of stress of stayed cables is small, so higher stress can be adopt In common case, stayed cable's stress of cable-stayed bridge is 0.4-0.45 times standard strength, but that of partial cable-stayed bridge is 0.5-0.6 times, so steel amount can be reduced.7 Construction method of main beam of partial cable-stayed bridge is analogical to those of girder bridge. Because it has bigger bending stiffness, construction method of general girder bridge can be adopt . It does not need to use larger suspended wangon, so it is more safe for building.8 Its applicable span is between 100~300m. If main beam adopts mixed concrete and steel structure, the span will reach 400m.