What is sub structure and super in bridges?

In bridge construction, the terms "substructure" and "superstructure" refer to the two main structural components of a bridge. Here's an explanation of each:

1. Substructure:

The substructure of a bridge is the part that supports the superstructure and transfers its loads to the ground or underlying foundation. It consists of the following elements:

a) Foundations: The foundation is the lowest part of the bridge that transmits the loads from the superstructure to the ground. Foundations can be shallow, such as spread footings or pile foundations, or deep foundations like piers or caissons, depending on the soil conditions and bridge design.

b) Piers: Piers are vertical structural supports that rise from the foundation and help support the superstructure. They are typically made of concrete, stone, or steel and can be hollow or solid. Piers transfer the weight of the bridge deck and traffic loads to the foundation.

c) Abutments: Abutments are structures built at the ends of the bridge where it meets the ground. They provide lateral support to the bridge deck and retain the earth behind them, preventing it from spilling onto the roadway.

2. Superstructure:

The superstructure is the part of the bridge that spans the open space between the substructures. It consists of various elements that work together to carry the traffic loads and provide a smooth and safe passage for vehicles and pedestrians.

a) Bridge Deck: The bridge deck is the horizontal surface that vehicles travel on. It is typically made of concrete, asphalt, or steel and is supported by the supporting beams or trusses.

b) Girders: Girders are horizontal structural members that support the bridge deck and transfer the loads to the piers or abutments. They can be made of steel, concrete, or timber and are typically spaced at regular intervals.

c) Trusses: Trusses are triangular-shaped structural frameworks that provide support for the bridge deck. They are commonly used in longer-span bridges and consist of a series of interconnected members that form a rigid framework.

d) Cables or Arches: In some bridge designs, cables or arches are used instead of girders or trusses to support the bridge deck. Cable-stayed bridges utilize high-strength cables to suspend the deck from tall towers, while arch bridges rely on the arch-shaped structure to transfer loads to the ground.

The substructure and superstructure of a bridge work together to ensure the stability and safety of the entire structure. The design and construction of these components must carefully consider factors such as the bridge's location, traffic loads, environmental conditions, and the nature of the terrain below.