Different types of bridges constructed in the world are discussed in the article. Nature of construction, load distribution, types of materials used for construction, and types of loads applied on the bridge are few factors that affect the selection of the types of bridges.
Let’s see what the criteria available for the categorization of bridges.
- Types of construction material – steel, concrete, timber, prestressing, etc.
- Structural form – truss, beams, suspension, cantilever, etc.
- According to the purpose of use – Road bridge, highway bridge, railway bridge, pedestrian, etc
- According to spans of bridges – culvert bridge, major span bride, long-span bridge, etc.
There are many other methods that can be used to classify the bridges. Above are some of the commons methods used to identify types of bridges.
Let’s discuss the types of bridges in detail.
Truss Bridge
A truss is a structure that transfers the loads as axial forces. It does not subject to bending and shear actions.
Depending arrangement of the trusses there is different classifications.
Let’s see what are the main components of the truss bridge.
Figure from Wikipedia
The above figure indicates the basic components of the truss bridge. There are other components such as deck bracings to increase the lateral stiffness of the bridge.
Let’s briefly discuss different types of truss bridges.
Howe Truss Bridge
Hower truss could be constructed from timber iron or steel.
It consists of vertical and diagonal members. The following figure taken from Wikipedia indicates the component of the shower truss bridge.
This is one of the old types of bridges that were widely used in the 1800s, and it is easy to desing. Even with a simple calculation, the design can be done.
Further, it is one of the economical types of bridges as it is easy to construct and its construction is not that complicated.
Pony Truss Bridge
This also a truss bridge.
Traffic is allowed to move through the truss and there are no bracings connected trusses on either side of the road.
This is not widely used in bridge construction due to the limitations in the spans. When the span of the bride increases, we need the lateral restraints for the truss. If no restrains, the bridge could be failing.
These types of bridges can be replaced with plate girder bridges and the span of the bride can be increased by modifying the lateral stiffness of the plate girders.
There are limitations in the span of these types of bridges.
Parker Truss Bridge
This type of bride is invented by Charles H. Parker. His name is used for these types of brides.
The top and bottom chords are not parallel. This is also a simple truss but two trusses on either side of the road are connected from the tops and bottom by horizontal and diagonal bracings.
K Truss Bridge
K truss bridge is a variant of the parker truss bridge.
Apparently, there are combinations of elements as the letter K.
Further, it element combination reduces the effective length of the elements. Vertical elements are connected by sloping elements to form the truss.
Bailey Truss Bridge
Bailey truss bridge is a temporary bridge stated constructed in the second world war era.
It is a portable-prefabricated-truss bridge. It can be removed from one location to another.
Even now during war, these types of bridges are constructed to cross the reviews, valises, embankments.
When we construct new bridges, bailey bridges are constructed for the bypass route.
Easy construction and the possibility to disassemble when required are the most important facts about these types of bridges.
Lattice Truss Bridge
A lattice bridge is a truss bridge that is constructed by placing diagonal members closely.
Further, these bridges are constructed from timber or steel.
Diagonally placed members carry the loads between the top and bottom chords.
These bridges can be observed in footbridges, railway bridges, etc.
In addition to the above types of truss bridges, there are many more types of truss bridges as discussed in the Wikipedia article truss bridge.
Cantilever Bridge
The cantilever action is taken into account when designing these types of bridges. Bridges is acting as cantilevered from the supports bear loads of the mid-span.
The following figure taken from Wikipedia is a simple example of how it maintains stability.
The truss action is the load transfer mechanism in these types of bridges.
Mainly there are two abutments at the mid-span of the bridge and then the bridge is cantilevered from these piers. There may be several piers of this nature depending on the total length of the bridge.
Mainly there are the following components of these types of bridges.
- Anchor Arm – which provide the stability for the cantilever action. It balances the rotation induced by the cantilever arm.
- Cantilever Arm – The main component of the bridge is the cantilever arm. It supports the bridge. The suspended portion in the bridge is supported by the cantilever arm.
- Suspended Span – It is supported by the cantilever arms from either side of the bridge.
These bridges are constructed from structural steel and sections such as universal beam sections, H sections, rectangular hollow sections, circular hollow sections, etc are widely used as the members of the bridge.
The above figure indicates a typical cantilever bridge. There are different architecture have different appearance while maintaining the functional and structural requirements.
Further, it is comparatively easy to construct these types of bridges than the other types of bridges as we can continue construction from one abutment toward the mid-span.
Once both sides are completed, the suspended span can be placed by connecting both the cantilevers.
In addition, when there are requirements for headroom for the movements across the bridge, these types of bridges are more useful as the nature of this bridge provides it.
Suspension Bridge – Cable-Stayed Bridge
Suspension bridges are also called cable-stayed bridges are types of bridges constructed to support large spans.
The bridge deck is supported by vertically hanging cables which supported by cables supported in between the piers/abutments.
The following components can be observed in a suspension bridge.
- Main Cable
The cable running on top of the bridge connecting all the components of the bridge and anchored at the ends is the main cable.
It is the element that carries loads of the bridge to the supporting structures and it can be identified as the key elements of the bridge.
It is a combination of steel wires and there are thousands of wires in the main cable.
- Suspender Cables
Suspender cables are also made from the same material. It is also a combination of steel wires. However, these cables are not that thick as the main cable.
These cables are used to hag the deck on the main cable.
- Deck
The deck is the area where the movement of people or vehicles are allowed.
The deck is a combination of steel trusses and girders.
Trusses and bracings connected between trusses for the stability of the deck are hanging on the main cable by suspender cables.
- Towers
The tower is the main component that supports the suspension cable. The key span of the bridge is maintained between the towers.
It also is known as the pylon.
Mostly the towers are made of concrete or steel and it is the tallest part of the bridge.
- Anchors
Anchors are the concrete blocks that support the cable at ends.
The tensile force on the cable is supported by the anchor block rest on the ground which may be founded on a pile foundation.
Suspension bridges or cable-stayed bridges are desing for three limits states.
The main cable is the main component that needs to concentrate on these limit states.
- Ultimate limit state design for cable tension
- Serviceability limit state for tensile stresses and strains, sag and vibration
- Fatigue limit state for traffic loading and wind actions.
The following type of actions is considered when designing a suspension bridge.
- Dead loads – self-weight of the structure
- Traffic Load – Necessary traffic loads shall be considered as per the relevant standards.
- Wind Loads – Wind is one of the key load cases that need to the considered in the desing. Lateral loads applied in a horizontal direction create vibration in the bridge. It could level lead to failure of the bridge. Therefore, necessary modifications to the bridge shall be done to avoid failures due to wind. Further, wind tunnel tests are also carried out to know the behavior of the structure. Thus countermeasure shall be taken to avoid the vibrations induced due to winds.
Advantages of Suspension Bridges
- The main advantage of the cable-stayed bridge is the possibility of having long spans. Not like other types of bridges, we can have a larger span between two abutments or piers.
- The nature of this bridge has reduced the quantity of material to be used when compared with other types of bridge. It could reduce the cost of construction.
- Movement along the river is not obstructed by the bridge.
- Comparatively less involvement in the ground level construction in the river section other than laying the cables.
Disadvantages of Suspension Bridges
- Higher stiffness is required for the bridge deck to avoid wind-induced vibrations. Since the span is very high, we have to have a stiffer system to bear the aerodynamic actions.
- There is a difficulty in having high traffic due to the low stiffness of the bridge deck.
- The cost of the foundation is comparatively higher.
Arch Bridge
One of the oldest types of bridges can be identified as arch bridges. There are different types of bridges fallen into this category.
The load from the structure and the other applied loads are transferred to the abutment through the arching action.
There are different types of bridges constructed from different materials. When it starts to construct the arch bridges, there was no concrete. Therefore, different techniques are used in construction.
Masonry arches, rock arches, etc are constructed in a stable manner to support the superstructure of the bridge. These materials are weak in tension. Therefore, the arch is constructed in a manner that the loads will be transferred as compressive forces.
Let’s see what are the common types of arch bridges.
- Corbel arch bridge
- Deck arch bridge
- Through arch bridge
- Tied-arch bridge
- Moment tie arch bridge
- Fixed – Fixed concrete arch bridges
- Pin – Pin concrete arch bridges
- Aqueduct and Chanel Viaduct
Modern arch bridges are constructed from concrete, steel, or a combination of both materials though the old bridge was constructed as masonry structures consist of brick or rubble.
Beam Bridge
Construction of the bridge using the beams falls under this category.
Different types of beams are used to construct the beam bridges.
- Reinforced concrete beams
- Univeral beams – steel
- Plate girder
- Post-tensioned beam
- Pre-tensioned beam
- Box Girder
Reinforced Concrete Beam Bridges
As we all know, reinforced concrete has limitations. When the span of the bridge increases, we have to increase the depth of the beam.
In addition, the area of reinforcement also needs to be increased. It is not a cost-effective option to consider for larger spans.
Especially on highways, there are heavy loads to be considered for the design. In such situations, concrete beams may not be cost-effective when the span of the bridges is also larger.
Therefore, reinforced concrete beam bridges are more suitable to consider for spans less than 10m.
When applicable deep beams can be used to support the bridge as suitable.
Universal Beam
The universal beam is a steel beam having a web height more than the flange.
Steel beams are placed on the abutment at regular spacing as required by the desing and then the deck of the bridge will be placed.
Usually, these types of beams are constructed as composite beams by taking into account the composite action of the slab.
When the composite action is not taken into account, steel beams are desing as usually beam as per the relevant standards.
Steel beam design worked example could be referred to get to know the procedures to be followed in beam design. This example is done for BS 5950, and design shall be done as per the relevant standard.
Plate Girder
Plate girders are widely used in bridge construction. They are made of steel and they are fabricated beams.
Not like the rolled section, fabrication can be done as per the requirement of the bridge.
The article plate girder could be referred for further information on this subject.
Post Tensioned Beam
Post tension beams are the most commonly used types of beams used in different types of bridges.
After constructing the concrete beam, post-tensioning is done and then they are launched.
Not like other types of beams, post-tension beams can be used to support large spans. Most of the medium-scale bridges are constructed from post-tension bridges.
The worked example Post tension beam design could be referred for more information on the procedure to be followed in designing a post-tensioned beam.
Box Girder
Box girder is a widely used type of bridge beam when there are large spans to be supported.
Further, they are used in the suspension bridges too.
Usually, the box girder bridges are post-tensioned. Further, they are the best type of bridge beam that can resist torsional moments effectively.
Therefore, box girder bridges are more effective in curved bridges.
Bascule Bridge
The bascule bridge is constructed when we need to make allowance for movement through the river. Therefore, these types of bridges are also called lifting bridges.
When required, the bridge can be lifted, and then it can be lowered for vehicle movements.
There are many famous bridges such as London Tower Bridge in the world.
The counterweights fixed on the bridge helps the movement of the bridge in the vertical direction. In addition, there are man other methods used to have a rotation of the bridge at the abutment.
Culvert Bridge
Culverts are types of brides constructed worldwide as short span bridges.
The nature of the construction of the culvers is used to categorize them.
The following types of culvert bridges can be commonly observed in the world.
- Pipe Culverts – One or several pipes are placed together to create the bridge. Generally, the concrete will be poured between the pipes to make it a complete bridge.
- Pipe Arch Culvert – Part of the pipe is constructed as the arch. This is more similar to the old arch bridges. There could be single or several arches in the bridge.
- Box Culvert – It is a concrete box-type structure that allows the movement of water through the box and traffic on the top slab of the box. Depending on the span of the canal, there could be single or several boxes.
- Bridge Culvert – It is constructed the same as the bridge but it is like a box culvert bridge too. There are abutments constructed the same as the bridge.
Footbridge
It is a small scale bridge that is constructed for passenger movement only.
Old days those bridges were constructed by members. Later they were mostly constructed from steel, concrete, and timber.
Further, large spanning footbridges are constructed as suspension bridges.
The following types of bridges are construed as footbridges.
- Beam bride
- Boardwalk
- Clapper Bridge
- Moon Bridge
- Simple suspension Bridge
There are many other types but the above are common types that can be observed.