Challenges in the Design and Implementation of a Steel Beam Launcher for Precast Girders Assembly

ACCIONA has designed and built a Steel Beam Launcher for Precast Beam Assembly. The structure consists of two steel trusses of triangular tridimensional structure 110.90 m long and 3.755 m high. The hoist load capacity of the Beam Launcher is 110 tons and the maximum span between supports is 52 m. The main challenge for the design of the Beam Launcher has been to guarantee the safety of the works in all the maneuvers to be carried out, taking into account the determining longitudinal slope of the viaducts up to 6.0%. To take on this challenge, the Beam Launcher has been designed with a rack‐and‐pinion system, which ensures total safety in the maneuvers. The Beam Launcher has also been designed to develop all the operations required for the assembly of the Viaducts, such as lateral load of the precast beams from barges, front and rear feed of the Beam Launcher from the adjacent span and front and rear feed from a truck located on the previously poured deck. Besides, the Beam Launcher is modular to adapt to the different spans of the Viaducts, extending and decreasing its length when needed. This modular requirement governs the design of the joints in the Beam Launcher: the connections between diagonals and main chords are pinned and the connections between modules are prestressed, using both prestressed bolts and prestressed bars depending on the demanding forces.