| As a new kind of combined structural system bridge, the cable-stayed arch bridge has both merits of the cable-stayed bridge and the arch bridge, but its mechanical properties are more complicated and different from them. There is no such bridge style constructed in the world at present. Combined with the engineering practice and taking the example of the Fourth Bridge over Xiangjiang River in Xiangtan city, this paper gives the study and discussion about the static character, ultimate bearing capacity and seismic resistance of cable-stayed arch bridge. The main research work covers the following aspects:(1) First, this paper generalizes the approximate formulas for in-plane basic frequency of some bridge style. With the principle of the minimum potential energy, the approximate formula for in-plane basic frequency of the cable-stayed arch bridge has been deduced. The influences of various factors on in-plane basic frequency of the cable-stayed arch bridge are discussed. These factors include the locations of the support, the number of the cables, the ratio of rise to span for the arch.(2) With the help of ANSYS, one universal FEM software, the 3-D finite element model of the Fourth Bridge over Xiangjiang River in Xiangtan city is established. This paper calculates the structural internal forces of the bridge considering linearity, geometric nonlinearity and material nonlinearity individually. The effects of various factors such as the shape of the cables, steel ratio of the arch, cable force and so on are discussed.(3) Considering the double nonlinearity, the ultimate bearing capacity of the cable-stayed arch bridge is analyzed. The effects of various factors such as cable force, initial imperfection of the arch, materials strength, the rigidity of lateral connections and so on are discussed.(4) Under the different direction seismic excitation, the seismic behaviors of the cable-stayed arch bridge are analyzed by using the response spectrum theory and time history method respectively.
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