The‌ ‌Components‌ ‌of‌ ‌a‌ ‌Standard‌ ‌Road‌ ‌Bridge‌

 

Bridges are a critical component of a country's infrastructure because they allow the transportation of raw resources and completed commodities to manufacturers. Bridges also make it easier for people to buy goods and services in their local areas and elsewhere. When a bridge closes, economic activity slows or stops entirely.

The most typical materials for these types of structures are metal-based or concrete. Metal, in particular, is always in high demand due to the many advantages of steel. Other bridges require specialized materials or products for maintenance and quality purposes like steel with neoprene gasket due to its resistance to the elements.

Although there are still bridges made of other materials like wood, these are few and now uncommon. Despite the differences, most of these structures possess similar components and parts due to their same function. These similarities are standard, as seen in many designs built today.

The Components of a Bridge

There are three main components for a bridge's standard structure:

1. Bearings

2. Superstructure Components

3. Substructure Components

Bearings

Now you might be wondering why this component is first on the discussion. It is the middle part of the structure and what separates the superstructure from the substructure. Naturally, anything above the bearing is a superstructure component, while anything underneath it is the substructure, which includes the foundation.

With the help of bearings, the loads received by the decks get appropriately and safely transmitted to the substructure. These are bridge components that allow for even load distribution on the substructure material. This transfer is critical for circumstances where the substructure does not have the design to take the load action directly.

The loads acting on the bearing, the level of maintenance, the geometry, the clearance provided, rotation, the displacement, deflection policies, accessibility, the designer's choice, the construction limitations, and the cost requirements all play a role in bearing selection.

The bridge's bearings enable the girders to move longitudinally. The forces acting in this direction produce this motion. The principal causes of longitudinal forces are forces caused by moving loads and temperature variations.

Superstructure Components

The bridge's superstructure composition comprises deck slabs, trusses, and girders, among other things. These elements differ depending on the type of bridge, whether concrete, steel, or composite. The supported weight passing over the bridge is by the superstructure. This way aids in the transmission of the loads' forces to the substructures underneath.

Deck slabs: Decks bear the brunt of direct traffic. The utilization of concrete and metal is typical to construct simple decks. Examples are walking or travel paths, drainage systems, expansion components, curbs, approach slabs, and sidewalks.

Trusses: The composition is of triangular elements, joined together to distribute loads and bending moments throughout the bridge. Suspension trusses, simple trusses, and cantilever trusses are a few examples. The truss network, which one can create as a deck, through, or pony truss, provides a surface for transit. The way traffic moves on the bridge is different for each truss.

Girders: By extending over the pile caps, girders connect them all. Known typically as beams, they reinforce the deck. Depending on the length of the bridge, it can be a single or numerous spans connecting all of the bents. A truss design is commonly for girders to enhance stress and load resistance. As a result, the transfer of pressure will immediately go to the foundation. The most utilized are metal or concrete girders.

Arches: A bridge design that comes with arches is incredibly sturdy. It can help manage the bridge's safety and load-bearing capacity. The number of arches and the materials utilized in their construction is critical. The spandrel is the gap between the bridge pillars and the deck beam. Depending on the arch design, the spandrels can be open or closed.

Suspensions: This bridge supports vertical weights using tensioned curved cables. It distributes these loads to the towers, which carry them to the ground via vertical compression and the anchorages, which must withstand the cables' inward and sometimes steep pull. 

Only the towers are in compression; thus, the suspension bridge looks like an upside-down arch in tension. Because the deck is in the air, it must have careful monitoring to avoid moving too much when loaded. It results in the deck needing to be either heavy, stiff, or both.

Substructure Components

These are the components underneath the bridge which include piers, abutments, wing walls, and foundation. This bridge part bears the superstructure and transfers all bridge loads to the bridge footings below ground. In short, it's the solid structure upon which the bridge rests. 

Piers: These vertical structures support the deck or offer bearings for stress transfer through the foundation to the underground earth. At intermediate places, these structures act as supports for the bridge spans. The pier structure serves primarily two purposes:

1. Stress displacement to the foundation

2. Resistance to horizontal forces

This structure's design is to withstand vertical loads alone in the majority of circumstances. In seismic zones, the advice is that the pier should also have considerations for lateral stresses. The majority of it is concrete, but there are instances of steel utilized in its construction in only a few situations. 

The usage of composite columns, which are steel columns filled with concrete, is a novel pier construction technology. The pier is a vertical element with a shear mechanism that resists forces. The majority of these forces are lateral. The term "bent" refers to a pier made up of numerous columns.

Abutments: These are vertical structures that hold the earth in place behind a design. The bridge abutments support the live and dead loads from the superstructure. They are also subject to lateral forces, which generate mainly from the approach embankment. The primary purpose of the abutments is to prevent sliding and overturning. 

The whole system's stability is receiving more attention. The foundations of abutments must be with considerable concentration and considerations. There must be a resolution of the differential settlement and excessive movements induced by lateral forces or loads through the abutment foundation.

Wing Walls: These are structures built as extensions of the abutments to hold the ground in the approach bank. The rest of this section will be at a natural angle of repose. These are retaining walls built alongside the abutments. The construction of this wall can be in conjunction with the abutment wall or separately. 

Its resistance to active earth pressures primarily determines the wing wall's stability. The structural components of the bridges must have the required designs built to withstand resting earth pressures.

Foundations: The weight from the piers, wing walls, and abutments gets distributed uniformly over the strata by foundations. The foundations for bridge structures are deep enough to prevent water movement scouring and limit the risk of undermining.

Conclusion

Bridges are essential for transportation. As a result, there's a need to research the bridge design's finalization, complicated calculations, and an in-depth feasibility study. The bridge design must consider different factors such as the environment, load capacity, soil type and preservation, material, building approaches, and procedures.

To have peace of mind when building such structures, you need a solid piece of advice from licensed professionals and their teams. Trust a professional with years of experience and reputable background, and always double-check the ones you think will give the best options for you.

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