Bridge piers are important structures that support the bridge superstructure and transfer loads to the foundation. They are designed to be both strong and visually appealing, and should not impede water flow or tide if the bridge spans over water. Commonly constructed using concrete, stone, or metal, concrete is often the preferred choice for submerged piers due to metal’s tendency to rust in water. Bridge piers can vary in shape and size, and are designed based on factors such as aesthetics, site conditions, available space, and economic constraints. The designer must ensure that the pier’s shape is appropriate for the specific application, taking into account load-bearing requirements as well as potential effects on river water flow or other external forces such as high winds.
Fig. 2: Pier Cross-section Shapes for River and Waterway Crossings
Types of Bridge Piers
Based on the Structure of Piers
Both solid and open piers can be further categorized into different types depending on their design and construction. For example, solid piers can be built as rectangular, circular, or square-shaped, and can have different types of foundations such as spread footings, pile foundations, or drilled shafts. Open piers can be designed as truss piers, which use a network of diagonal members to create a stable structure, or as frame piers, which use a series of columns and beams to support the weight of the bridge.
Overall, the type of pier that is chosen for a particular bridge project will depend on a variety of factors such as the site conditions, the size and weight of the bridge, and the materials and resources available for construction.
1. Solid Piers
Solid piers are sturdy and impenetrable structures that can be constructed using various materials such as bricks, stone masonry, mass concrete, or reinforced concrete. These types of piers are known for their durability and strength.
Solid piers can be classified into two categories: solid masonry piers and solid reinforced concrete piers. Both types of piers have a robust and impermeable structure, making them suitable for use in a variety of applications. Solid masonry piers are constructed using bricks or stone masonry, while solid reinforced concrete piers are made of reinforced concrete.
1.1 Solid Masonry Piers
The solid masonry pier is made using a combination of brick masonry, stone masonry, and concrete. To keep costs down, the exterior of the pier is constructed using stone masonry, while the interior is filled with mass concrete. This approach allows for a sturdy structure that is both cost-effective and durable. By using stone masonry for the outer layer, the pier is able to withstand external forces and provide protection to the inner core of the structure. Meanwhile, the use of mass concrete for the interior provides added strength and stability to the pier. Overall, this construction technique is an effective solution for creating solid masonry piers that are both strong and affordable.
1.2 Solid Reinforced Concrete Piers
Solid reinforced concrete piers are a popular choice for construction projects that require tall support structures. These piers are typically rectangular in shape and are made from reinforced concrete. The reason for choosing this type of pier is that solid masonry piers may not be strong enough to support the weight of the structure when the height of the piers exceeds a certain point. Additionally, constructing masonry piers of this height can be uneconomical. Therefore, reinforced concrete piers are a more practical and cost-effective solution for such projects.
2. Open Piers
Open piers are a type of structure that allows water to pass through them. These piers are classified into different types based on their design and functionality. Unlike closed piers, which completely block the flow of water, open piers allow water to flow through them, which makes them particularly useful in certain settings.
The different types of open piers vary in their construction and use. Some may be designed to support bridges or other structures while allowing water to pass underneath. Others may be used to protect shorelines from erosion, providing a barrier that still allows water to flow through. Still others may be used to create artificial reefs, promoting marine life and biodiversity in areas where they might not otherwise thrive.
Overall, open piers offer a unique solution to a variety of engineering and environmental challenges. By allowing water to pass through, they can provide important benefits while minimizing the negative impacts of more closed structures. As such, they remain an important part of many coastal and marine environments around the world.
2.1 Cylindrical Piers
The cylindrical pier is a type of pier that is constructed using a cylinder made of cast iron or mild steel which is then filled with concrete. It is typically used for bridges that have a moderate height. To enhance stability, horizontal and diagonal steel bracing may be incorporated in certain cases.
2.2 Column Piers or Column Bent
The column bent pier is a suitable option for bridges that have a significant height. This pier consists of a cap beam and supporting columns, which together form a frame. This type of pier can be used to support a steel girder superstructure, or it can be used as an integral pier if the cast-in-place construction technique is employed.
Circular or rectangular columns can be used for this type of pier, and it is currently the most popular form of pier used in modern highway systems.
2.3 Multicolumn or Pile Bent
Multicolumn, pile bent, or frame bent piers consist of multiple columns that support a cap. To ensure stability and proper weight distribution, isolating footings are typically used for these types of piers when there is a significant spacing between the columns. However, if the spacing is relatively small, a combined footing may be more appropriate.
One issue that can arise with multicolumn piers is the collection of debris between the columns when water is allowed to flow through them. This can potentially cause blockages and interfere with the flow of water. To mitigate this problem, strategies such as adding grates or screens to the pier design may be employed to prevent debris from accumulating.
2.4 Pile Pier or Pile Bents
The modification of multicolumn bent known as pile pier is commonly used for short span structures with low height. These pile piers are particularly specified in situations where the ground is unstable and low piers are needed.
The main purpose of pile piers is to provide stability to the structure by distributing the weight of the structure evenly to the ground. This is especially important in areas where the ground is not strong enough to support the weight of the structure. Pile piers are also used in situations where the span of the structure is short and the height of the piers needs to be low.
Compared to other types of piers, pile piers are relatively easy to construct and require less material. They are made by driving piles into the ground and then capping them with a pier cap. This process ensures that the weight of the structure is evenly distributed to the piles, which then transfer the load to the ground.
Overall, pile piers are a practical solution for low height and short span structures built on unstable ground. They provide stability to the structure and ensure that it is safely supported by the ground, making them an essential component of many construction projects.
2.5 Trestle Pier or Trestle Bent
The Trestle Pier is designed with columns and a bent cap at the top, making it an ideal choice for bridge construction in areas where the river bed is stable and water currents are slow. Additionally, this type of pier is commonly used in the construction of flyovers and elevated roads.
Fig. 10: Pile Trestle
Original: “Construction materials play a crucial role in the quality, durability, and sustainability of built structures. The selection of appropriate construction materials is essential for ensuring the structural integrity of a building or infrastructure project. These materials include concrete, steel, wood, masonry, glass, plastics, and composites, among others. Each material has its own unique properties and characteristics, making it suitable for specific applications. For example, concrete is commonly used for its strength and durability, while steel is favored for its high tensile strength. Wood is often used for its natural aesthetic appeal and sustainability, while masonry provides excellent fire resistance. The choice of construction materials also affects the environmental impact of a project, as some materials may be more eco-friendly or energy-efficient than others. Therefore, careful consideration of construction materials is essential in the design and construction process to ensure that the built environment is safe, durable, and sustainable.”
Rewritten: “The quality, durability, and sustainability of built structures greatly depend on the appropriate selection of construction materials. Concrete, steel, wood, masonry, glass, plastics, and composites are among the materials used in construction, each with its own unique properties and characteristics tailored for specific applications. For instance, concrete is chosen for its strength and durability, steel for its high tensile strength, wood for its natural aesthetic appeal and sustainability, and masonry for its excellent fire resistance. The environmental impact of a project is also influenced by the choice of construction materials, with some materials being more eco-friendly or energy-efficient than others. Hence, careful consideration of construction materials during the design and construction process is crucial to ensure that the built environment is safe, durable, and sustainable.”
3. Masonry Piers
Masonry piers, which may include stone masonry and brick masonry, are typically constructed to be massive structures. However, their size can create problems such as obstructing linear waterways and increasing the loads on foundations. To mitigate these issues, masonry solid shaft piers are built on open raft foundations, which eliminate the possibility of scour. Alternatively, pile foundations can also be used for such types of piers.
4. Mass Concrete Piers
Mass concrete piers are similar to masonry piers in their massive size, which can obstruct linear waterways and increase loads on foundations. However, pile foundations can be utilized for mass concrete piers to address this issue.
Another option for constructing mass concrete solid shaft piers is an open raft foundation, as long as scouring is not expected. It’s important to note that no reinforcement is needed for structural purposes in mass concrete piers, but nominal reinforcement is typically provided to address potential temperature and shrinkage effects.
5. Reinforced and Prestressed Concrete Piers
Reinforced concrete and prestressed concrete piers are designed with smaller cross-sectional areas compared to masonry and mass concrete piers. This design feature allows them to require less foundation area while also creating less obstruction to waterway traffic. These types of piers are especially suitable for major bridges where the span and depth are considerable, and where the piers must be as light as possible while maintaining maximum section modulus.
When constructing reinforced concrete piers, it is important to ensure that the percentage of longitudinal reinforcement falls within a specific range. Specifically, the reinforcement should be neither less than 0.8% nor more than 8% of the gross cross-sectional area. In situations where brick and stone materials are expensive, reinforced concrete or prestressed concrete piers are often the most cost-effective solution.
6. Fixed Piers
There are fixed piers that are designed to support a fixed bearing. These piers are capable of withstanding both transverse and longitudinal forces.
7. Free Piers
A pier that is free supports a bearing that is also free and is responsible for transferring only axial forces from the bearing to the foundations.
8. Hammerhead or Cantilevered Piers
A hammerhead pier, which is also referred to as a solid shaft pier, is a type of pier used to support steel girders or precast prestressed concrete superstructures. It features a single solid concrete cross section that serves as the foundation for a cap that is placed on top of it. This pier is commonly used in urban areas where space is limited. Due to its compact design, it occupies minimal space and provides more room for traffic underneath.
Typically, spread footings are recommended as a foundation for hammerhead piers. The solid shaft pier’s major axis should be aligned in the direction of the stream flow, or else a circular or small rectangular cross section may be chosen instead. The standards for the use of hammerhead piers are usually maintained by individual transportation departments.
9. Special Shaped Bent
10. V Shaped Concrete Pier
11. V Shaped Steel pier
