Sydney Harbour Bridge, arguably the most famous of this type |
|
| Ancestor | Truss arch bridge |
|---|---|
| Related | None(see Suspension bridge) |
| Descendant | Tilt bridge |
| Carries | Pedestrians, vehicles, light rail, sometimes heavy rail |
| Span range | Medium |
| Material | Steel |
| Movable | No |
| Design effort | High |
| Falsework required | Seldom |
A through arch bridge, also known as a half-through arch bridge and through-type arch bridge, is a bridge made from materials such as steel or reinforced concrete in which an arch rises above the deck so it passes through the arch. Cables in tension suspend the deck from the arch.
One of the most famous bridges of this type is the Sydney Harbour Bridge in Australia. The Hell Gate Bridge in New York City, the Bayonne Bridge in New Jersey, which is longer than the Sydney Harbour Bridge, as well as the smaller, near-twin Bourne Bridge and Sagamore Bridge over the Cape Cod Canal, are very similar.
In some locations it is not practical to support the arch from beneath during construction.
In modern construction, temporary towers are erected and supported by cables anchored in the ground. Temporary cables fly from each side to support arch segments as they are constructed. When the arches are almost complete a jacking bridge is placed over or beneath the gap to force the arches apart, whence the final section is constructed in place or lifted into position.
In some cases, this type of arch has been created by constructing cantilevers from each side, with the shoreside ends bolted securely down into heavy piers. The incomplete channel ends are then constructed toward each other and either filled by construction or by lifting a prefabricated center section. This type of construction can be seen in the Sydney Harbour Bridge illustrated above.