Step 6. Calculate the UL stringer.
Step 7. Determine the maximum shoring spacing.
(a) Spacing based on stringer strength. Refer to
(b) Spacing based on the shoring strength and
end bearing of the stringer, based on the
allowable load in tables 3-5 and 3-6.
Allowable load based onshore strength. (See
Allowable load based on end bearing
stresses. (See table 3-6.) Since we do not
know what species of wood we are using,
you must assume the most critical and lowest
compression perpendicular to the grain
equals 250, and the allowable load for a 4 by
4 (S4S) equals 3,100 pounds.
Select the most critical load.
Determine shore spacing based on allowable
Select the most critical shore spacing. The
spacing determined in step (7(a)) is less than
the spacing determined in step (7(b));
therefore, the shore spacing to be used is 35
Step 8. Shore deflection check.
Therefore, lateral and cross bracing are not required.
Step 9. Summary.
Sheathing: 3/4-inch plywood
Joists: 4" x 4" (S4S) lumber spaced@ 22 inch
Stringers: 4" x 4" (S4S) lumber spaced @ 55
Shores: 4 x 4 (S4S) lumber spaced@ 35 inch
Bracing: Not Required
BEAM FORM DESIGN
Beam forms, like slab forms, carry a vertical
load, and they are also subjected to the lateral
pressure of freshly placed concrete just as wall
forms are. Beams can be formed independently to
span walls and columns or monolithically (one
continuous pour) as part of a floor slab system.
When formed as part of a slab system, a part of the
load from the slab forms may be carried by the beam
form to the supporting shores and must be accounted
for in the formwork design.
Figure 3-5 shows atypical interior beam form with
slab forming supported on the beam sides. This
drawing indicates that 3/4-inch plywood serves as the
beam sides and that the beam bottom is a solid piece
of 2-inch dimension lumber supported on the bottom
by 4- by 4-inch T-head shores.
Close examination of figure 3-5 shows that when
a beam is to be formed as part of a slab system, some
of the design procedures have been completed. For
example, the lateral pressure against the beam sides is
compensated for by the slab joists which butts against
the beam sides and rests on the attached ledger. All
that remains to complete the design of a beam form is
to determine the design load for which the form must
be designed. Knowing the design load, the maximum
allowable bottom sheathing span (shore spacing) for
the materials available can be determined. Next the
total load per shore can be determined and the design