Abstract:Based on the mechanical property of cable stayed suspension bridges, a reasonable and simplified model is established and the deflection expression of girder beam of multi tower cable stayed suspension bridge under live load is deduced in view of the gravity stiffness theory of suspension bridge. Then, some approximate formulats are presented, including maximum deflection of girder beam, displacement of the top of middle town, the axis force of main cable and the safety coefficient of restricting cable slide and so on. In order to verify the approximate formulas, three dimensional finite element models which are established, which are analyzed with finite element software ANSYS. These models involve typical cable stayed suspension bridges, such as three towered bridges with different main spans, which are 600, 1 080 and 1 400 m, and the 1 400 m main span bridges of different numbers of towers ranging from 2 to 6. In comparison with the results of finite element analysis, the result of this investigation clarifies the maximum error of the key mechanic parameters calculated by the proposed approximate formulas is within 15% for three towered cable stayed suspension, 20% for bridges over four towers.
