1.4. Structural Elements

1.4.1 Tie Rods:

• Subjected to tensile force only.
• They are slender.
• They are referred to as “tie rods” and “bracing ties”.
• They are made from bars, angles, and channels.
• Strength is limited only by material strength.

Tie rods are structural elements specifically designed to withstand tension, meaning they primarily bear pulling forces. Their slender forms help them be both lightweight and efficient. They can be made out of various materials like steel bars and channels, and their allowable load capacity is determined solely by the strength of the material from which they are made. They play a crucial role in stabilizing structures by providing necessary support without adding excessive weight.

Imagine a suspension bridge where the cables hang down and connect to the bridge deck. Those cables act like tie rods, pulling up on the bridge to keep it from sagging under the weight. Just as those cables are critical in tension, tie rods are essential components in many structures, ensuring they remain taut and stable.

1.4.2 Beams:

• Usually straight, horizontal members used to resist bending moments and shear forces.
• Classified to the way they are supported.
• Resist shear force and bending moment.

Beams are critical structural components that typically run horizontally in buildings and structures. Their primary function is to support loads and resist bending moments. Bending moments occur when forces are applied that twist or bend the beam, while shear forces are those that act parallel to the surface. The classification of beams depends on their support arrangements, such as cantilevered, simply supported, or fixed beams, each of which behaves differently under load.

Consider a bookshelf sagging under the weight of books. The horizontal planks acting as shelves are like beams. They need to be strong enough to resist bending as books are added. If they were too weak, they would bend or break, just like a small beam would fail under an excessive load.

1.4.3 Columns:

• Vertical elements resisting axial compressive loads.
• When subjected to both bending moments and axial load, they are referred to as “beam column”.
• Susceptible to buckling which limits the strength of the member.

Columns serve as vertical supports in structures, carrying loads down to the foundation. They are specifically designed to handle compressive forces, which push down on them. However, if a column is too slender, it might buckle under load, losing its structural integrity. When a column also experiences bending moments (like those sometimes seen in beams), it is referred to as a 'beam column,' signifying that it needs to account for both axial and bending effects in analysis and design.

Think about a tall tower of blocks. If you stack too many blocks (load) on top of a single block (column), that block could buckle under the pressure. Similarly, in a building, when vertical columns support the weight of the floors above, they must be robust enough to avoid buckling under the heavy loads they encounter.

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