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

166 Chapter Six
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placed near mid-height of unbraced shores or midway between
points of lateral support.
Patented Shores
Patented shores are more commonly used than job-fabricated wood
shores for supporting formwork for concrete beams and slabs. When
compared with wood shores, they have several advantages and several
disadvantages.
The advantages of patented shores include the following:
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1. They are available in several basic lengths.
2. They are readily adjustable over a wide range of lengths.
3. For most of them, adjustments in length can be made in small
increments.
4. In general, they are rugged, which ensures a long life.
5. The shore heads are usually long enough to give large bearing
areas between the shores and the stringers that rest on
them.
Among the disadvantages of patented shores are the following:
1. The initial cost is higher than for wood shores.
2. For some, but not all, it is more difficult to attach intermediate
braces than it is for wood shores.
3. Because of their slenderness, some of them are less resistant
to buckling than wood shores.
Ellis Shores
The method of shoring of this company consists of two 4 × 4 S4S
wood posts, fastened by two special patented clamps. The bottom of
one post rests on the supporting floor, whereas the second post is
moved upward along the side of the lower one. Two metal clamps,
made by Ellis Construction Specialties, are installed around the two
posts, as illustrated in Figure 6-1. The top post is raised to the desired
height, and the two clamps automatically grip the two posts and hold
them in position.
The shore specifications include lower shore members composed
of two Ellis clamps with pivotal plates, permanently attached with
threaded nails near the top, 12 in. apart, center to center. The upper
shore member is of sufficient length to obtain the desired height. Both
the lower and upper members are No. 1 grade Douglas Fir or Yellow
Pine, free of heart center, stained with ends squared.
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