Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

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Shores and Scaffolding 175
FIGURE 6-6 Tubular steel scaffolding to support formwork. (Source: Symons
Corporation)
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Most types of steel scaffolding can be either rented or purchased. Due
to the high initial investment cost of scaffolding, its purchase is not economically
justifiable unless the scaffolding will be used a great many times
and at frequent intervals. Many contractors buy a reasonable quantity of
scaffolding and rent additional units to suit the needs of a particular job.
Commercial frames are usually available in several widths, varying
from 2 to 5 ft for standard size frames, depending on the manufacturer.
Each frame consists of two legs with heights that vary from
2 to 6 ft per frame, in increments of 1 ft. Up to three frames can be
stacked on top of each other to obtain a three-tier shoring system.
The rated safe load capacity is generally around 10,000 lb per leg,
or 20,000 lb per frame. The load capacity will increase or decrease
depending on the actual number of tiers used and the total extension
of the jacks. The manufacturer should be consulted to determine the
safe load capacity for each job application.
Diagonal cross braces are available in lengths which are multiples
of 1 ft, such as 3, 4, 5, 6, or 7 ft, to brace frames. Locking devices are used
to securely attach diagonal braces. Screw jacks allow fine adjustments
of the height of the frames. Figure 6-7 illustrates standard shore frames
available from the Symons Corporation.
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