Some representative post-tensioned box girder bridges are constructed by IL M
(Incremental Launching Method), FCM (Free Cantilever Method or Balanced
Cantilever Method), MSS (Movable Scaffolding System), etc. FCM is generally used in a terrain where obstacles such as rivers, creeks and roads lie under the bridge, which present difficulties in installing conventional shoring. FCM is generally used for long span bridges, which are typically accompanied with high piers. Since it involves constructing balanced cantilevers from a pier, it is often referred to as a balanced cantilever bridge.
Similar to any other segmental construction methods, FCM presents structural system changes in each construction stage, and each structural system needs to be analyzed throughout the construction process. The analyses also must reflect time dependent material properties, tendon relaxation, tension losses in tendons, etc., whose effects are then accumulated through the various stages of construction.
In this tutorial, MID AS/Civil FC M Wizard is used to model construction sequence; analysis is performed; and, results for stresses, prestress losses and deflections are reviewed in construction stages.