Bridge

Bridges

A structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath.

Purpose of bridges

Providing passage over the physical obstacle which is usually something that is difficult or impossible to cross.

History

They began being constructed in the ancient times when mordern civilizations started rising in Mesopotamia. From then on knowledge, engeneering and manufacturing of new bridge building materials sperad beyond their borders enabling bridges’ slow but steady adoption worldwide.

Ancient roman bridge

The architecture was the discovering of arches. Using this type of building, load forces of the bridge were conveyed to move along the curve of the arch, meeting with the ground where supports on the end of the arch cancelled them, Because of that Romans were able to create bridges that were much lighter than before and holds twice as heavy as the bridge itself. Roman architects even managed to create water carrying bridges with multiple arched tiers that reached incredible heights!

Types of bridges

1. Arch bridge

2. Beam bridge

3. Cantilever bridge

4. Suspension bridge

5. Cable stayed bridge

6. Tied arch bridge

7. Truss bridge

Arch bridge

The romans bult more than 1000 stone arch bridges, some are still standng like the Pont-Saint-Martin bridge in Italys Aosta Valley (built in the first century BCE). This bridge design dates back more than 3000 years. Concrete is now also used to build mordern arch bridges.

Beam bridge

It was the first type of bridge ever built. It s the cheapest to build. All you need is a crossbeam covering the span, supported by an abument at eahc end. One type is a girder bridge which emplys steel grinders as reinforcement

Cantilever bridge

This type uses a pillar anchored vertically into the ground to support a horizontal deck extending out from one or both sides across the span. The load often is supported from both above and below.

The worlds largest cantilever span is the quebec bridge in canada which was built in 1919 and extends 1800 feet.

Suspension bridge

They are stabilized with vertical pillars or pylons connected by suspension cables. Attached to these main cables are smaller, vertical suspenders that hold up the bridge deck using tension, the main force that sustains suspension bridges.

Example the golden gate bridge

Cable-stayed bridge

A variation on the suspension bridge that connects the crossbeam or bridge deck directly to pillars or towers. Theres no main cable, just a large number of vertical suspenders affixed to the top of the tower. These suspenders use tension to help the bridge deck stable and in place

Example Stromsund Bridge in Sweden

Tied-arch bridge

It combines features of an arch bridge and a suspension bridge. It uses horizontal thrust from both sides to support an arched structure, as in a regular arch bridge. But instead of an arch supporting the structure from below. The arch rises above the road and vertical ties descend to increase support of the decking.

They are also called bowstring bridges since they look like a bow from the side. This bow uses the tension of its vertical cables, together with tje compression of the arch, to support the load and keep the bridge stable.

Truss bridge

It distributes its load across a series of small sections fitted together. Formed by structural beams for smaller bridges or box girders for larger ones, bridge trusses are typically bound together by welded or riveted joints in a series of triangles.

E.g Cottonwood River Pratt Truss Bridge in Cedar Point, Kansas