Placing Reinforcing Bars

Steel is strong in

tension, compression and shear (3-1)

Reinforced concrete is a combination of

both reinforcing steel and concrete that uses best properties of each, namely the compressive strength of concrete and the tensile strength, or pull resistance, of steel (3-1)

Piles

used where the subgrade is not firm enough to provide adequate bearing for a foundation. (4-3)

Piles are driven to the required depth and support the load by

end-bearing and friction of the subgrade material against the surface of the pile (also called skin friction) (4-3)

The most common types of piles are:

reinforced precast concrete
reinforced precast-prestressed concrete
concrete cast in driven steel casings
cast-in-place concrete in holes drilled or bored into earth
steel pipes or steel H-beams
timber, plain or treated
(4-3)

Continuous Beams (or Slabs)

extend over more than one span and deflect downward between supports. They have reverse curvature of each interior support. This requires tension reinforcing steel in the bottom of the beam between supports and in the top of the beam over the supports (6-5)

Steel for reinforced concrete is usually

deformed bars, commonly referred to as reinforcing bars, re-steel or rebar, varying from 3/8 inch to 2-1/2 inches in diameter; Welded wire reinforcement (plain or deformed) with wire area from W1.4 or D4 to W45 or D45; Tendons for post-tensioned concrete; and strand for prestressed concrete are also used, mainly in combination with reinforcing bars (3-1)

Temperature and Shrinkage Steel (or T & S Steel)

Placing reinforcing steel in slabs at right angles to the main stress resisting steel to provide for induced stresses (6-8)

The most common use of reinforcing steel is to

resist compression forces in columns (6-8)

If concrete were used by itself, without reinforcing steel

the size of column required would be so large that it would be impractical and add considerable weight to the structure (6-8)

Because reinforcing bars are about twenty times stronger than an equivalent area of concrete, they are

used to resist part of the column load (6-8)

When the concrete and reinforcing steel work together, the resulting column is

smaller in size and lighter in weight (6-8)

In some beams where compression is high or where the size of the beam is restricted, it may be necessary to use

longitudinal reinforcing bars in the top of the beam (6-9)

Yield Strength

the load limit to which steel will stretch and return to its original length (much the same as stretching a rubber band) (6-10)

Tensile Strength

the load limit at which steel breaks (6-10)

To obtain uniformity throughout the United States,

the ASTM has prepared standard specifications for reinforcing bars (7-3)

Deformed Bar

the standard type of reinforcing bar (7-1)