Creep Fibre Method of Simply-supported Composite Beams

Creep effects of composite beams can not be neglected in service-time. Creep Fiber method is used to obtain the time-depedent results, which proved to be quiet effect in both elastic and visco-elastic analysis. Only two individual centrical loading points or bars need considering, and then the system of two sumultaneous differential equations becomes simple in a clear fashion. It can be solved analyically by Rusch constitutive equation of creep. For high and large beams of bridge structures the fibres of the two points are constant over time because the radius of inertial of steel beam is far larger than that of concrete slab, which simplifies the procedure further. The results show that under sustained loading creep of concrete produces significant negative effects. It may increase the modular ratio to 2.3 times of the initial, reduce the whole flexural stiffness by 76%, and cause the local buckling risk of the top flange and web of steel beam. These should be considered in the design of structure.