The new Belleair Beach Causeway Bridge in Belleair Beach, Florida was constructed to replace the existing bascule bridge spanning the Gulf Intracoastal Waterway. Included in the design for the new 3350-foot bridge were 75-foot long approach spans. The original bridge design for the approaches was post-tensioned cast-in-place concrete built on falsework, but a desire for a more economical approach prompted the contractor to offer, and the owner to accept, the incremental launch method. VSL was employed to assist with the design, provide the systems and the technical supervision for the project, and run the stressing operations.

The incremental launching method is one of the more highly mechanized erection methods used in bridge construction. It consists of building the superstructure segments sequentially in a casting bed located behind the bridge abutment. Each segment is cast against the previous one and prestressed with concentric post-tensioning to the section of superstructure already built. The entire superstructure is then jacked forward a distance equal to the length of this segment which is half a span length. The process is repeated until the bridge is in its final position. Additional continuity prestress is then installed and the temporary bearings are replaced by the permanent bearings.

Mobilization and set-up of the casting bed for the approach spans took approximately three weeks. Once the bed was established and the crew gained experience with the construction method, work proceeded on a defined schedule. Segments were cast on a one week cycle. Most of the construction operations took place in the same location – easily organized as a precasting yard. This arrangement allowed work to continue in inclement weather and to be easily supervised.