Before segmental construction entered everyday vocabulary, one project quietly transformed bridge erection. Across the tidal flats of western France, Jean Müller and Campenon-Bernard built the Oléron Viaduct (Pont de l'île d'Oléron) — a 2.86 km prestressed-concrete structure on which, according to a 2006 PCI Journal profile of Müller, a launching gantry was designed for the first time to erect a superstructure in balanced cantilever (poutre de lancement).

2.86 km
Structure length
46
Spans
79 m
Typical main span
1964
Construction start
Constraint 1
Traditional barge or crane lifting was impractical given the shifting tidal conditions of the Coureau d'Oléron. The site dictated the method.
Müller's solution
A self-launching overhead steel gantry placing precast segments symmetrically either side of each pier — balanced-cantilever erection — with segments delivered along the completed deck, avoiding all contact with the water below.
Precision erection
Each segment was lifted, aligned, and post-tensioned with high geometric precision — entirely from above, without touching the water below.

The concept proved that large viaducts could be erected entirely from above, safely and efficiently — setting the template for modern launching gantries used worldwide today.

The principle Müller demonstrated at Oléron — that precast segments could be erected in balanced cantilever by an overhead gantry working from the completed structure — became the foundation for subsequent launching gantry development worldwide. The site constraints that appeared to make the project impractical were what forced the invention.

The erection principle proven at the Coureau d'Oléron set the template for how major viaducts are built from above. The method was not adopted because it was obvious. It was adopted because it was demonstrated — here, with precision, under tidal constraint, for the first time.

For further reading on erection engineering applied to bridge construction, see Erection Engineering in Bridge Construction, which places the launching-gantry method used here in a wider sector context.

Related case studies: Akashi Kaikyō Bridge · Woronora River Bridge · Chenab Bridge

Core concepts: What is erection engineering? · What is heavy lift engineering?

The Oleron Viaduct's precast box-girder deck seen from below and behind, carried on a line of tapered concrete piers across the Coureau d'Oleron
The Oléron Viaduct across the Coureau d'Oléron. Its precast segmental deck was erected using the pioneering self-advancing launching gantry described here.
Photo: Mutichou / Wikimedia Commons, CC BY-SA 3.0.
Four-panel schematic of the Oleron Viaduct balanced-cantilever erection sequence: gantry travelling on completed deck toward the next pier, precast voussoirs placed symmetrically either side of that pier, tendons stressed to lock the segment pair, then the gantry advancing to the following pier
Balanced-cantilever erection sequence, Oléron Viaduct, 1964–66: the gantry travels on completed deck, places precast voussoirs symmetrically at the active pier, tendons lock the pair, then the gantry advances.
Original diagram, EE&HL Network. Simplified schematic, not to scale.

Sources: Structurae — structural data and construction dates for the 1964–1966 works; PCI Journal — Tassin, D.M., “Jean M. Muller: Bridge Engineer with Flair for the Art Form”, March–April 2006 — balanced-cantilever erection with a launching gantry, site constraints. Figures are reported as published.