Calculation of initial pretension for a cable-stayed bridge using ‘Cable Force Tuning’ function in midas Civil

  • Bridge Engineering
  • midas Civil
  • 2013.05.13
  • A cable-stayed bridge is a structural system that effectively combines cables, girders and the pylon into an esthetically pleasing structure. It is a versatile bridge type since different pylon forms and cable layout forms can be adopted depending on the surrounding environment.

    By inducing initial pretension to the cables, it can reduce the moments acting on the girders and make a light long span bridge possible. The calculation of the initial pretension of the cables can be difficult and complicated,  and  in  the  past  the  initial  pretension  was  determined  by  the  designer’s  discretion, experimental values, etc.

    The ‘Unknown Load Factor’ function in midas Civil calculates the initial pretension that needs to be applied to the cables for a cable-stayed bridge. However, with the ‘Unknown Load Factor’ the designer cannot get the desired initial pretension in one step. The designer should do many iterations by fine-tuning the pretension using the influence matrix in order to get the initial pretension that produces the desired bending moments and deformations.

    ‘Cable Force Tuning’ in midas Civil is a function that makes the iteration process required for the design of the bridge easy.

    ‘Cable Force Tuning’ allows the user to adjust the cable force and to check the displacements of the girders or the pylon in real time, without reanalyzing.

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