“Pul”,” Paalam”, “Pont”, “Setu”. Call them by any name, bridges are quintessential design elements in architecture. Bridges are historically significant such as the London Bridge, Howrah Bridge, Bukka’s Aqueduct, etc.
Bridges span across water bodies, vast lands, and even between buildings. However, all bridges are connected by their singular purpose- to aid users in crossing over obstacles.
Why does each bridge look different if all bridges serve a single purpose? Let’s look into 7 types of bridges, their construction, and their specific application.
Arch Bridge
Beam Bridge
Cantilever Bridge
Cable-stayed Bridge
Suspension Bridge
Tied-Arch Bridge
Truss Bridge
Every bridge faces two loads; the dead load which is the load of the bridge itself, and the live load which is the load that the bridge carries.
1. Arch Bridge
An arch bridge uses gravitational force and load, to hold up the bridge.
It conveys the downward pressure to the center of the structure, towards a keystone.
This is called compression, which supports the deck above it.
Arch bridges are long-span bridges.
Pont du Gard, France (Built by Romans)
2. Beam Bridge
The cheapest of all bridges to build.
It is a crossbeam, supported by an abutment at the ends.
Tension is the main force acting on the bridge.
As the span of the bridge increases, the beam’s abutments cannot hold and stabilise the bridge.
Thus, there are piers or stanchions at intervals to add stability.
Lake Pontchartrain Causeway, Louisiana, U.S.A
3. Cantilever Bridge
The bridge deck is anchored vertically by a pillar, and extends horizontally on both ends.
The load is supported from above and below.
Cantilever bridges are usually combined with the other types, for providing stability.
Trusses are added to take the load off the deck and pass to the piers and abutments.
Howrah Bridge, Kolkata
4. Cable-Stayed Bridge
A variation of a suspension bridge connects the crossbeam or deck directly to the pillars or towers.
Rather than having the main cable, it has vertical suspenders, fixed to the top of the tower.
They use tension to keep the bridge stable.
5. Suspension Bridge
Suspension bridges have pillars or pylons to stabilise the deck.
There are smaller vertical suspenders that hold up the bridges using tension.
Suspension bridges can be affected by resonance, created by wind movement. It can create vibrations.
It can also be affected by torsion, a force that twists the bridge.
Shear force affects the bridge horizontally.
Golden Gate Bridge, San Francisco
6. Tied-Arch Bridge
It is a combination of an arch and suspension bridge.
It uses horizontal thrust to support an arched structure.
However, there is an arch that rises above the road, instead of below the deck, and vertical ties descend to increase stability.
Godavari Arch Bridge, Andhra Pradesh
7. Truss Bridge
The load is distributed across a series of small sections fitted together.
Bridge trusses are bound together by welded or riveted joints, in a series of triangles.
There are vertical steel or wooden supports to hold up the bridge, using tension.
A diagonal truss adds stability, using compression.
Bridges come in every shape and size, but in totality, they serve the purpose of connecting across obstacles, efficiently. They add interest to a space, are a significant part of the ambiance, and shape the architecture.
Bridges can show the history of a region, or even be the inspiration for designing the surrounding spaces.
