Understanding Structure Components: Substructure vs. Superstructure

Structures are typically divided into two main parts relative to the ground level: the part below the ground and the part above the ground. These parts have specific technical names in civil engineering and construction.

Let's define the key terms related to parts of a structure:

• Substructure: This refers to the portion of the structure that is located below the ground level. Its primary purpose is to transfer the loads from the superstructure to the foundation and then safely distribute these loads to the supporting soil or rock. Examples include foundations (like footings, piles, rafts), retaining walls, and basement walls below ground.
• Superstructure: This refers to the portion of the structure that is located above the ground level. This is the visible part of the building or structure where activities take place. Examples include beams, columns, slabs, walls, roofs, and stairs above the ground floor.

The question asks for the term used for the portions of the structure below the ground level. Based on the definitions, the correct term is Sub-structure.

Analyzing the Options

Let's look at the provided options:

1. Submerged Structures: This term usually refers to structures that are built or exist entirely underwater, such as offshore platforms, submarines, or submerged tunnels. While parts of a substructure might be below groundwater level, the term "submerged structure" specifically emphasizes being under a body of water, not just below ground.
2. Sub-structures: As defined above, this is the standard term for the part of a structure located below the ground level.
3. Sustainable Structures: This refers to structures designed and built using environmentally friendly processes and resource-efficient materials throughout a building's life-cycle, from siting to design, construction, operation, maintenance, renovation, and deconstruction. This term describes a characteristic of the structure regarding its environmental impact, not its location relative to the ground.
4. Super-structures: This refers to the part of the structure located above the ground level, which is the opposite of what the question asks for.

Therefore, the term for the portions of the structure below the ground level is Sub-structures.

Conclusion on Structure Components

The division of a structure into substructure and superstructure is fundamental in structural design and construction. The substructure is critical as it ensures the stability and safety of the entire structure by properly anchoring it to the ground and handling the transfer of all applied loads.

Revision Table: Structure Below Ground Level

Additional Information: Foundation Systems

The substructure includes the foundation system, which is the lowest part of the substructure that directly interfaces with the supporting soil or rock. Foundation systems are broadly classified into two types:

• Shallow Foundations: These are used when stable soil bearing strata are available relatively close to the ground surface. Types include isolated footings, combined footings, strip footings, and raft or mat foundations.
• Deep Foundations: These are used when the stable bearing strata are located far below the ground surface or when the loads are very high. Types include piles, piers, and caissons. The choice of foundation type depends on the soil conditions, the type and magnitude of the loads from the superstructure, and economic considerations.

Understanding the substructure and its components, like the foundation, is vital for ensuring the overall stability, settlement performance, and safety of any built structure.