Span-by-Span Erection of Precast Segmental Bridges: Twin-Girder Overhead Self-Launching Gantries

The vast majority of precast segmental bridges are erected span-by-span with self-launching gantries. Twin-girder overhead gantries provide unrivalled versatility in large-scale highway projects, light-rail transit projects, urban bridges in median, marine operations, and other conditions of reduced clearance under the bridge.

In 31 pages, the eManual explores the main components of a twin-girder overhead gantry, the pros and cons of modular trusses and box girders, the use of hangers and spreader beams to hold the segments in-place during application of epoxy, and the support and launch systems of the gantry. The eManual also discusses loads, self-launch kinematics, performance, productivity, span cycle time, the labor demand for the different temporary static schemes of staged construction, and the pros and cons of simultaneous erection of adjacent decks by side shifting the gantry on wide pier crossbeams.

The eManual explores the stability of tall bridge piers under the loads applied by pier brackets, the stiffness interactions to consider for the design of piers and superstructures, and staged application of post-tensioning to avoid opening of the epoxy joints and the risk of brittle span failure.

• Introduction
• Loading, kinematics, typical features
• Support, launch and lock systems
• Performance and productivity
• Structure-equipment interaction
• References

The eManual provides exhaustive coverage of the topic for bridge owners, designers and construction professionals interested in span-by-span construction of precast segmental bridges. Other monographs of the eManuals Project discuss segment fabrication, the span assembly operations common to all families of self-launching gantries, and the other types of self-launching gantries used for span-by-span construction.

The collection Span-by-Span Construction of Precast Segmental Bridges (134 pages) provides exhaustive coverage of span-by-span construction, ranging from segment fabrication to the different types of self-launching gantries used for span erection, and is offered with 10% discount on the cover price of the five eManuals.