Introduction to Reinforced Concrete Design

by ce on December 19, 2011

Concrete is the most widely used construction material in the world. Right now, it is estimated that 6 billion tons concrete are produced annually. Some characteristics that make concrete the popular choice to be used in construction are:

  • Except cement, the raw materials such as fine and coarse aggregates, water are readily available locally.
  • Versatile in terms of shape, color and texture
  • Design flexibility in term of structural system that can be chosen to suit a particular condition such as using one-way or two-way slabs.
  • Relatively durable against harsh environment such as against sea water.
  • High compressive strength
  • Good fire resistance
  • Last but not the least, the use of concrete materials normally results in economical structures.

As you have learned from concrete technology, usual concrete is produced by combining cement, aggregates and water. The reaction between cement and water will produce cement paste that is getting hard with the time and acts as binder to the aggregates, thus producing rock-liked solid. Nowadays one or more admixtures are added to achieve certain characteristics such as workability, setting and durability.

Concrete has a high compressive strength and a low tensile strength. This led to the invention of reinforced concrete, which is a combination of concrete and steel in which steel provides the tensile strength lacking in concrete. In addition, steel can also carry the compressive load as found in column structures.

The combination of concrete and steel in reinforced concrete produces a structural element that take the advantage of each material. The high tensile capacity of steel is used to overcome the low strength of concrete. On the other hand, the high resistance of concrete against corrosive environment is used to protect steel, which is prone to corrosion. Also both concrete and steel are bonded together very well, thus able to resist the load as a unit. This excellent bond is achieved by chemical adhesion between two materials, the surface roughness and closely spaced ribs along steel.

To produce good reinforced concrete elements, concrete and steel must be of good quality. Mix design for concrete must be prepared such that the produced concrete satisfy the workability, strength, and exposure condition requirements. Workability is normally measured in term of slump. Exposure condition will determine the concrete strength and concrete cover. The concrete slump and strength are required to prepare the concrete mix design. The steel is produced in factory and normally in good quality. However, we still need to make sure that the steels are clean and not corroded.

Finally, to design usual reinforced concrete, we must followed design codes. In the United States, the design code for reinforced concrete design is called the American Concrete Institute’s Building Code Requirements for Structural Concrete (ACI). In Australia, it is called AS 3600 Concrete Structures. In Europe, it is Eurocode Concrete. The design codes basically provide design constraints and accepted analysis methods.

{ 1 comment… read it below or add one }

terapot May 16, 2012 at 10:18 am

ok

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