What is a Reinforced Concrete Framed Structure?

Reinforced Concrete Structures are one of the most popular structural elements. It is very much competitive with steel if economically designed and executed practically where labour for centering and formwork is cheap. The philosophy for Reinforced Concrete Structures tells that Concrete is strong in compression but very weak in tension. Hence for simplicity of design, its tensile strength is neglected. Wherever tension occurs cracks are likely to occur perpendicular to the tensile force. Hence, steel reinforcement is provided and all tension is considered to be resisted by steel. Due to tension developed by moment, main reinforcement is placed on tension face to arrest the cracks and provide tensile strength to the member.

Advantages of Reinforced Concrete Structure are:

  • It is good in compression as compared to most other materials used for construction beside good in tension.
  • Its resistance to fire is better than steel so capable of resisting fire for a longer time.
  • It has a long service life with low maintenance cost.
  • In some structures like piers, dams and footings; it is the most economical structural material.
  • It can be cast to any shape required, making it most economical structural material.
  • It yields rigid members with minimum deflection.
  • The yield strength of steel is about 15 times the compressive strength of structural concrete and well over 100 times its tensile strength.
  • By using steel in concrete the cross-sectional dimension would get reduced.
  • Less skilled labors are required for erection as compared to other structural systems.

Disadvantages of Reinforced Concrete Structure are:

  • It needs meticulous mixing, casting and curing, all of which affect the final strength of the member.
  • The cost of formwork used to cast concrete is relatively high.
  • It has low compressive strength as compared to steel which leads to large sections of in columns/beams in multistory buildings, Cracks development in concrete due to shrinkage and the application of live loads is high.
  • If concreting is not done properly the steel starts corroding thereby loosing strength and ultimately the life gets reduced. Also the repairs are then very expensive and difficult.

The design of a structure may be regarded as the process of selecting proper materials and proportioned elements of the structure. In order to fulfill its purpose, the structure must meet its conditions of safety, serviceability, economy and functionality.

The two main methods of designing the Reinforced Structural System are:

  • Working Stress Method
  • Limit State Method

Codes for designing RCC Structure:

  • IS (Indian Standard) 456-2000
  • ACI (American Concrete Institute) 318-89
  • ICC (International Building Code) 2009
  • NZS (New Zealand Standard) 3101
  • Euro 2

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