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What is bridge pier? Its requirement and types.

 

A bridge pier is a sort of construction that reaches out to the ground beneath or into the water. It is utilized to help connect the superstructure and move the loads to the foundation. The bridge can be built to be considerably alluring and solid to withstand both vertical and even loads. It additionally doesn't prevent water stream or tide if the bridge traverses the water.

Bridge piers might be constructed utilizing solid, stone, or metal. Concrete is regularly indicated as development materials given that the pier is submerged in water since metal is inclined to rust in water. It is developed in numerous areas like streams, dry terrains on which roadway frameworks are worked as bridges

It can fluctuate in size and shape. It can also vary based on style, size, space, and monetary limitations, for example, bar and V shapes. The designer should indicate the suitable pier shape for a particular application. Now and then, bridge piers are intended to ensure appropriate burden direction of the street, and in different cases, it very well may be built in such a way that it would not forestall a legitimate flow of water stream. Furthermore, the plan of the bridge pier can be altered dependent on different powers that follow up on the extension, for example, high breezes that may uphold a specific plan over another.


Why bridge piers are required?

  • To effectively transfer loads from the superstructure to the foundation without fail.
  • To withstand all force actions.
  • To give stability against the longitudinal and lateral force action like seismic, wind, ice, current, impacts.

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Types of Bridge piers:

Based on the Piers structures:

Piers structures are classified into two types i.e solid piers and open piers. These are further classified into many types:

1. Solid Piers:

They are generally constructed from bricks, stone, masonry, reinforced, or mass concrete due to which they possess impermeable and solid structure. Solid piers are further classified into masonry piers and solid reinforced concrete piers.

a) Solid Masonry Piers:

As the name suggests these are constructed from stone masonry, brick masonry, and concrete. To make them economical the outer part is built from masonry like stone or brick while the inner part is filled with mass concrete.


b) Solid Reinforced Concrete Piers

These are mostly constructed from reinforced concrete and has generally rectangle shape. It is generally used where the height is more and the solid masonry piers won't be able to take the load.


Prestressed Concrete: What is it? When to use?

2.Open Piers:

These types of piers allow the water to pass through the structure and is classified as below:

a.  Cylindrical Piers:

These are constructed from mild steel or cast iron cylinder which are then filled with concrete. The cylindrical pier is suitable for moderate height bridges. Diagonal and horizontal bracing is used in certain cases to improve stability. 


b. Column Piers or Column Bent

Column piers are used for bridges with significant heights. It consists of supporting beams and a cap beam forming a frame. They can be either used to support a superstructure of steel girder or can be used as an integral part where the technique of cast-in-place construction is used. These piers are the most popular ones and can be either circular or rectangular in cross-section.


c. Multicolumn or Pile Bent

This type is composed of two or more columns that support a cap. The type of footing generally used is combined but if the spacing is large then Isolated footing is used. The problem encountered here is that the debris gets collected between the columns due to water flow.

d. Pile Pier or Piel Bents

This is a modification of multicolumn pier and is used on short span structure and low height. Piel piers are advised where the ground is not stable and low piers are needed.


e. Trestle Pier or Trestle Bent

This type of pier has a column with a bent cap on the top. It suits bridges where the bed of the river is firm and the current of water flow is slow. It is also used for elevated roads and flyovers.


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Based on Construction materials: 

1. Masonry Piers:

Masonry piers generally include brick or stone masonry. These piers are so massive that they may lead to obstruction of water flow and increase the load on the foundation. They are built on an open raft foundation where the scour possibility is nil. 

2. Mass Concrete Pier:

These are also massive and are similar to masonry piers. In this pile, foundations can be used for construction. Also, an open raft foundation can be used additionally for mass concrete piers with a condition that scouring is not anticipated. From a structural point of view no reinforcement is required but to prevent temperature and shrinkage effect nominal reinforcement is provided.

3. Reinforced and Prestressed Concrete Piers:

These piers have a small cross-sectional area as compared to mass concrete and masonry piers. This is the reason that such piers require less foundation area in addition to less obstruction to water flow.


They are suitable for major bridges where the depth and spans are considerable and the piers self-weight is to be minimum and the section modulus is as maximum as possible.

The percentage of longitudinal reinforcement should not be less than 0.8 nor more than 8% of the gross cross-sectional area. These piers are also used where the cost of brick and stone is high.

Based on Load Transfer Mechanism:

1. Fixed Pier:

These piers support a fixed bearing and are subjected to both longitudinal and traverse forces.

2. Free Piers:

Free Piers uphold free orientation and move just hub powers from the bearing to the foundations.

Others:

1. Hammerhead or Cantilevered Piers:

This type of pier has a single concrete cross-section upon which a cap is placed. It is generally used to support steel girders or precast prestressed concrete superstructures. It is constructed where there is a space limitation generally in urban areas. It has an aesthetic look besides occupying a small area and thereby allowing more traffic to flow underneath.

The spread footing is generally recommended for hammerhead piers. The direction of the solid shaft pier would be along the direction of the streamflow. These piers are often maintained by transportation departments.

2. Special shaped bent:


3. V-Shaped bent:


4. V-shaped Steel pier:


5. Architecture pier:




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