Construction Stage Analysis for FSM (Full Staging Method) using general functions

  • Bridge Engineering
  • midas Civil
  • 2012.09.13

 

FSM (Full Staging construction Method) is a very basic method in constructing post -tensioned concrete bridges. Dead weight of concrete, formwork and false work are fully shored over the full spans of a bridge until the concrete gains a certain level of strength.

FSM can be economical if the horizontal alignment of a bridge is curved or the width of the bridge deck widens, provided that the height of the piers are not too high.

In the case of a bridge with long spans, the use of continuous tendons can be limited, thereby requiring construction joints. Each segment may be constructed sequentially span by span. Structural analysis is carried out on the basis of construction stages defined by the construction joints. Although a bridge is supported by shoring, FSM is generally analyzed with the assumption that effect of support is negated by the effect of prestressing.

When FSM is applied to a bridge with continuous spans, the first stage is a simple span, and it becomes continuous with the progress of the construction stages. In comparison with an analysis that does  not  consider construction stages, the construction stage analysis results in lower negative support moments higher positive span moments. As such, a bridge constructed by FSM needs to be analyzed with construction stages reflecting both the change in structure, element load and boundary conditions  as well as time- dependent material properties, including creep, shrinkage and modulus of elasticity.


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