Depending on span length and the bridge length, this method is ideal for precast segmental or full span construction erected sequentially with launching gantries, overhead or underslung or on temporary supports, more seldom with twin cranes for full spans. The spans can be either simply supported or continuous over several piers and on bearings or monolithic with the piers, taking advantages of a frame action allowing a better use of the construction materials. Pre or post-tensioning allows the structures to be assembled efficiently and also provides substantial reduction of concrete and rebar materials. Spans are generally between 30 and 50 meters long, sometimes up to 60meters. Beyond this, cantilever construction (see below)  becomes more economical, except for very long spans (greater than say 800 meters) where suspension bridges then take over.

Span by span can also be made of longitudinal beams supporting the deck with spans between say 25 and 60 meters.

Applicable for long spans (generally greater than 60m) or shorter spans with tight curves. Beyond say 80meters, the deck might then be supported also with extradosed tendons or stay cable. Segments, either precast or cast-in-situ, are built in balance outwards from piers using form-traveler systems for in-situ structures or cranes or lifting frames of launching gantries for precast segmental construction. Cantilever structures are then connected at mid span with an in-situ stitch and post-tensioning tendons generally ensure continuity of the deck between piers. Decks are generally continuous over several spans and can either be resting on bearings or be rigidly connected to the piers, allowing a frame action. In special cases, cantilever may be assembled parallel to a road or a rail track and then rotated above that path in final position.

The deck, either concrete or steel or a combination of both, is prefabricated in subsequent sections connected together at the abutment and then launched over the piers using a front nose, lateral guides, temporary sliding bearings  and an heavy lifting system providing the motion to the structure. For concrete structures, the post-tensioning is arranged to allow the structure to take respectively positive and negative moments at each section.

This method is generally applicable for structures with constant geometry in plan and in elevation. It provides the least disruption to the traffic below. Spans are generally between 30 and 60 meters. In special cases, spans can be longer, but might require intermediate temporary towers or permanent or temporary stays for launching.

Heavy lifting is a very efficient construction method able to mobilize hundreds, sometimes, thousands of tons of capacity.

Individual precast spans or deck sections are lifted into position using strand jacks mounted on lifting frames or gantries. The method is particularly applicable for long droop-in spans or full spans between piers that can be lifted in one short operation mitigating disruption to the traffic below.

Each method can be combined with customized formwork, prefabrication setups, and launching equipment – including our modular systems and heavy-lifting technologies.