Reinforced concrete column is a good example of a composite bar.

Composite Bar:
A composite bar is a structural member made up of two or more materials with different properties combined together to form a single unit. These materials work together to enhance the overall performance and strength of the bar. The combination of materials allows the composite bar to utilize the best properties of each individual material.

Reinforced Concrete Column:
A reinforced concrete column is a composite bar made up of two materials: concrete and steel reinforcement.

1. Concrete:
Concrete is a composite material made up of cement, aggregates (such as sand and gravel), and water. It is known for its compressive strength and ability to withstand heavy loads. Concrete is used as the main structural material in the column.

2. Steel Reinforcement:
Steel reinforcement, typically in the form of steel bars or mesh, is embedded within the concrete to provide additional tensile strength. The steel reinforcement helps to resist tensile forces and prevent cracking or failure of the concrete.

Advantages of Reinforced Concrete Columns:
- Strength: The combination of concrete and steel reinforcement results in a high-strength composite material. The concrete provides compressive strength, while the steel reinforcement provides tensile strength, creating a strong and durable column.
- Ductility: Reinforced concrete columns have good ductility, meaning they can undergo large deformations without sudden failure. This is important in areas prone to earthquakes or other dynamic loads.
- Fire Resistance: Concrete has excellent fire resistance properties, while steel reinforcement helps to maintain the structural integrity of the column even at high temperatures.
- Durability: Reinforced concrete columns are resistant to corrosion and have a long lifespan, making them suitable for various applications.

Conclusion:
Among the given options, a reinforced concrete column is the best example of a composite bar. It combines the compressive strength of concrete with the tensile strength of steel reinforcement, resulting in a strong, durable, and versatile structural element.