Bridge Types

The five primary types of bridges are listed below according to
their support mechanism:

 1.      Girder
bridges

2.      bridges with
arches

3.      bridges with
cable stays

4.      Bridges with
Rigid Frames

5.      Bridges with
trusses

1. Girder bridges:

It is the most common and basic type of bridge. A girder bridge
can be as basic as a log spanning a stream; the two types of girders most
commonly encountered in steel girder bridges are I-beam and box girders.
Examining the section of the I-cross Beam validates its name. The vertical
plate in the middle is referred to as the web, while the top and bottom plates
are called flanges.

A box girder takes on the shape of a box. Usually, a box girder
has two webs and two flanges. Though this isn’t usually the case, the presence
of more than two webs results in a multiple chamber box girder. T-shaped
girders and pi girders—so named because they resemble the mathematical symbol
for pi—are two other examples of fundamental girders. Since most modern girder
bridges are built with box or I-beam girders, we won’t get into the specifics
of these more unusual scenarios.

An I-beam is quite simple to design and build, and it functions
very well in the majority of cases. Any curved bridge’s beams are impacted by
torque, which is just a synonym for twisting forces. The extra second web in a
box girder increases stability and resistance to twisting forces. Box girders
are therefore the greatest choice for bridges with any form of significant
curvature. Box girders are often used for greater spans in instances where
I-beams would not be strong or sturdy enough since they are more stable and can
cover larger distances.However, the design and construction of box girders are
more difficult than that of I beams. For example, to solder the internal seams
of the structure, a human or a welding robot needs to be able to operate inside
a box girder.

2. Arch bridges

After girder bridges, arch bridges are the oldest type of bridges
with a traditional architectural style. In contrast to standard girder bridges,
arches are excellent candidates for stone work. Arches are a wonderful option
for spanning rivers and valleys because they don’t need piers in the middle.
One of the most exquisite forms of bridges can be an arch. The curved framework
used by arches offers a strong resistance to bending forces. Because both ends
of an arch are fixed in the horizontal direction (i.e., no horizontal movement
is allowed in the bearing), unlike girder and truss bridges, arches can only be
utilized when the ground or foundation is solid and secure. Therefore,
horizontal forces arise in the arch’s bearings when a load is applied to the
bridge (such as when a car crosses it). In certain situations, the road may
cross an arch or go through one, just like a truss.

 
There are four main arch-type bridges in terms of structure:

1.      Without
hinges

2.      Two-faced

3.      Three swung
around

4.      Linked arches

The hinge-less arch does not have any hinges and does not permit
foundational rotation. Because of the enormous force (bending, vertical, and
horizontal) that is produced at the foundation, hinge-less arches can only be
constructed in areas with extremely stable ground. But compared to other
arches, the hinge-less arch is a much stiffer structure and experiences less
deflection. Hinge bearings are used in the two hinged arch to enable rotation.

Only vertical and horizontal forces are produced at the bearings.
This is probably the steel arches version that is utilized the most, and it’s a
pretty affordable design overall. An extra hinge is added to the top, or crown,
of the arch in a three-hinged arch. If there is movement in one of the
foundations (from sinking, earthquakes, etc.), the three-hinged arch is not
affected too much.

On the other hand, the three-hinged arch deflects significantly
more, and fabricating the intricate hinges can be challenging. These days,
three-hinged arches are seldom ever employed. An alternative to the arch that
permits building even in cases when the ground is not sufficiently firm to
withstand horizontal forces is the tied arch. As the girder “ties”
both ends of the arch together, it prevents the horizontal forces from being
restrained by the foundation, hence the term “tied arch.”

3. Bridges with cable stays:

The cable stayed bridge is an additional kind of bridge. A
continuous girder bridge with one or more towers placed above piers in the
middle of the span is a typical example of a cable-stayed bridge. Cables
support the girder by extending diagonally from these towers, usually to both
sides. Steel wires are incredibly flexible and robust. Because they enable a
lighter, more thin structure that can still span large distances, cables are
incredibly cost-effective. Even though there aren’t many cables strong enough
to hold up the entire bridge, they are vulnerable to a factor we don’t often
think about: the wind. 

Careful research is needed for longer span cable-stayed bridges to
ensure that the cables and the bridge will remain stable in the wind. The
bridge’s decreased weight is advantageous during an earthquake even though it
is a disadvantage in strong winds. Care must be given when planning the
foundations, though, as the cable-stayed bridge may sustain damage if uneven
settling of the foundations happens during an earthquake or over time. The
cable-stayed bridge is a visually appealing and distinctive landmark due to its
sleek and contemporary design.

The design of the bridge is an extremely difficult assignment
because of the special qualities of the cables and the structure overall.
Without the use of computers and computer analysis, the calculations for longer
spans where winds and temperatures must be taken into account would be
incredibly difficult and nearly impossible. Cable stay bridge construction is
likewise a challenging process. The girders and towers’ cable routing and
attachments are intricate structures that need to be fabricated with precision.
Cable-stayed bridges are not specifically categorized.

They may differentiate between them, nevertheless, based on
factors including the quantity of cables, girder type, spans, and towers. The
quantity and kind of towers, as well as the quantity and configuration of
cables, vary greatly. Single, double, portal, and even A-shaped towers are
frequently utilized. There are also wide variations in cable configurations.
Fan, star, harp, and mono arrangements are a few common types. Sometimes the
tower’s cables are simply fastened to one side of the girder, with the other
side secured to a foundation or other counterbalance.

4. Sturdy bridge frames: 

Mendes bridges are another name for rigid frame bridges. The piers
and the girder are two distinct structures of a typical girder bridge type. On
the other hand, a rigid frame bridge consists of a single, solid framework for
the girder and piers.

In a rigid frame bridge, the beam cross sections are typically I-
or box-shaped. Compared to basic girder bridges, rigid frame bridge design
calculations are more challenging. Fabricating the junction between the girder
and the pier can be challenging and demands precision and close attention to
detail.

Even though there are other alternative forms, the pi-shaped,
batter post, and V-shaped frames are the ones that are utilized practically
entirely these days. Because piers tilted at an angle can straddle the crossing
more efficiently without necessitating the building of foundations in the
center of rivers or piers in deep valleys, the batter post rigid frame bridge
is especially well suited for crossing rivers and valleys. Foundations are
effectively utilized by V-shaped frames. By providing two supports for the
girder, each V-shaped pier lowers the number of foundations and gives the
profile a less cluttered appearance. Inner city highway piers and supports are
often constructed using pi-shaped rigid frame systems. These bridges have a
frame that both supports the elevated highway and permits vehicles to pass
directly beneath it.

5. Truss bridges:

Truss bridges are the most prevalent type of bridge and are
typically found in steel bridges. A truss is made up of numerous tiny beams
that work together to sustain a significant weight and span a considerable
distance. Truss design, manufacture, and erection are often quite
straightforward processes. Trusses, however, require more room once completed
and may provide a traffic hazard in more intricate constructions. There are
both simple and continuous trusses, just like in girder bridges.

A truss bridge is the best option for locations where huge
sections or pieces cannot be supplied, or where large cranes and heavy
equipment cannot be used during construction due to its small individual parts.
Since the truss is a hollow skeleton, the road may run over or even through it,
providing clearance beneath the bridge that is frequently not achievable with
other kinds of bridges. The fundamental design that is employed also
categorizes trusses. The Warren, Pratt, and Howe trusses are the most exemplary
types of trusses. When it comes to basic and continuous trusses, the Warren
truss is arguably the most widely used. No vertical members are employed for
short spans, giving the construction a more straightforward appearance.

Vertical members are added for longer spans to provide additional
strength. Typically, Warren trusses are utilized for spans of fifty to one
hundred meters. The diagonal members of a Pratt truss all slant down and in
toward the center of the span, with the exception of the very end ones. All
diagonal members, with the exception of those close to the center, are solely
exposed to tension stresses; compressive forces are handled by the shorter
vertical members. Because of this, diagonal members can be made thinner,
leading to a more cost-effective design. In contrast to the Pratt truss, there
is the Howe truss. The diagonal elements support compressive forces and face
the other way. Because of this, it is a very expensive design for steel
bridges, and its application is uncommon.