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Structural Concrete Frames 361
Closure piece
Stirrup for
narrow beams
Stirrup with open top for
ease of fixing reinforcement
Top
reinforcement
Main reinforcement
Part of reinforcement
cage of beam
Figure 6.8 Stirrups to form reinforcement cage of beams.
thus saving time. Figure 6.8 is an illustration of part of a reinforcement cage for a reinforced
concrete beam.
The separate cages of reinforcement for individual beams and column lengths are made
up on site with the longitudinal reinforcement wired to the links with 1.6 mm soft iron
binding wire that is cut to short lengths, bent in the form of a hairpin, and looped and
twisted around all intersections to secure reinforcing bars to links. The ends of binding
wire must be flattened so that they do not protrude into the cover of concrete, where they
might cause rust staining. Considerable skill, care and labour are required in accurately
making up the reinforcing cages and assembling them in the formwork. This is one of the
disadvantages of reinforced concrete where unit labour costs are high. At the junction of
beams and columns, there is a considerable confusion of reinforcement, compounded by
large bars to provide structural continuity at the points of support and cranked bars for
shear resistance.