1.1 Description of Concrete Structures

Types of Load Bearing Concrete Structures

The advantages of reinforced concrete are cheapness of aggregates, flexibility of form, durability and low maintenance. 
A disadvantage is greater self weight as compared with steel, timber or aluminium.

The structures are essentially composed of load bearing frames and members which resist the actions imposed on the structure: 

• self weight
• dead loads
• external imposed loads (wind, snow, traffic etc.).

Load Bearing Members

A load bearing frame is composed of load bearing members

• Beams
• Columns

Structural elements are required to resist forces and dispacements and may act:

• tension
• compression
• flexure
• shear
• torsion
• or in any combination of these forces

The structural behaviour of a reinforced concrete element depends on the nature of the forces, the length and shape of the cross section of the member, elastic and plastic properties of the material, yield strength of the steel, crushing strength of the concrete and crack widths.

Connections

The structural elements are made to act as a frame by connections. 

For reinforced concrete, these are composed of reinforcing:

• bars bent
• lapped
• welded

which are arranged to resist the forces involved. A connection may be subject to any combination of axial force, shear force and bending moment in relation to three perpendicular axes, but for simplicity, where appropriate, the situation is reduced to forces in one plane.