seabridge

Seabridge refers to a bridge or causeway that spans a sea, strait, or other marine body to connect two landmasses. In civil engineering, seabridges are designed to withstand marine conditions while carrying road or rail traffic and often to provide navigational clearance beneath or around the structure. The term can denote both fixed, long-span structures and floating or modular solutions, depending on geography, depth, and navigational requirements.

Common forms include suspension and cable-stayed bridges for long spans, and arch or truss bridges for shorter spans. In shallow or heavily navigable waters, longer causeways or viaducts may be used. Seabridges may include protective measures such as seawalls, tidal gates, and scour protection at foundations. Materials commonly employed are steel and concrete, with coatings and protective systems to counter saltwater corrosion. Design must address wind, waves, currents, earthquakes, and environmental impact, as well as maintenance access and maritime traffic priorities. Construction challenges include foundation work in soft seabeds, deep-water placement, and ongoing corrosion protection.

Notable sea-crossing bridges include the Øresund Bridge between Denmark and Sweden, the Great Belt Bridge in Denmark, and the Akashi Kaikyō Bridge in Japan. These examples illustrate varying approaches to span length, clearance, and multi-modal use.

The term seabridge is also used as a proper name in some contexts, such as Seabridge Gold, Inc., a Canadian mining company. It is unrelated to maritime infrastructure in that usage.