Short Answer:

Columns can be classified based on load type and reinforcement arrangement. Based on load, columns are categorized as axially loaded columns, unaxially loaded columns, and biaxially loaded columns. Based on reinforcement, columns are classified into tied columns, spiral columns, and composite columns.

Axially loaded columns carry load along their center axis, while unaxial and biaxial columns carry loads along one or both directions with bending. Tied and spiral columns differ in how the reinforcement is provided around the main bars. These types help engineers choose the right column design for safe and strong structures.

Detailed Explanation:

Types of columns based on load and reinforcement

Columns are vertical structural elements in buildings and bridges that transfer the weight of the structure to the foundation. In reinforced cement concrete (RCC) design, columns are classified in different ways depending on the type of load they carry and the reinforcement arrangement they contain.

This classification helps in understanding the behavior of the column under load and ensures proper design for stability, strength, and durability. Let’s discuss both classifications in simple terms.

Types of Columns Based on Load

1. Axially Loaded Column

• The load acts exactly along the centerline (axis) of the column.
• There is no bending moment in this type of column.
• Stress is evenly distributed across the cross-section.
• This is the simplest type of column in theory but rarely exists in actual structures because of accidental eccentricities.

Example: Columns in basement walls or in center of symmetrical structures.

2. Uniaxial Eccentric Loaded Column

• Load acts with eccentricity (offset) in one direction from the centerline.
• The column experiences both axial load and bending moment in one direction.
• Most common in real structures where beams frame into columns on one side only.

Example: Columns at building corners or along walls.

3. Biaxial Eccentric Loaded Column

• Load acts with eccentricity in both directions from the centerline.
• The column undergoes axial compression and bending in two directions.
• This is more complex and usually occurs at intersections of beams from different directions.

Example: Columns at junctions of beams in multi-bay structures.

Types of Columns Based on Reinforcement

1. Tied Column

• Has main longitudinal bars with lateral ties (closed loops) to hold them.
• Ties are placed at regular spacing along the height of the column.
• Most commonly used in buildings due to simple construction and economy.
• Ties prevent buckling and hold the core concrete in position.

Example: Common RCC columns in residential and commercial buildings.

2. Spiral Column

• Main bars are surrounded by continuous helical spiral reinforcement instead of closed ties.
• The spiral offers better confinement, increases ductility and load capacity.
• Suitable for circular columns and columns in seismic zones.

Example: Columns in bridges or earthquake-resistant buildings.

3. Composite Column

• Made using a combination of steel sections and concrete.
• Can be a steel section encased in concrete or a concrete core with external steel reinforcement.
• Used in high-rise buildings where high strength and reduced cross-section are needed.

Example: Columns in industrial structures or metro stations.

Conclusion:

Columns are classified based on how they carry loads and how their reinforcement is arranged. Load-based types include axially loaded, uniaxially, and biaxially loaded columns. Reinforcement-based types include tied, spiral, and composite columns. Understanding these classifications helps engineers select the right type of column to ensure strength, stability, and safety in various building structures.