TM 5-809-12/AFM 88-3, Chap. 15
(2) Special joint between new and existing
considered as an alternate to the special joint; how-
floors. A special thickened-edge joint design (fig 5-
ever, a thickened-edge design will be used for the
13) will be used at the juncture of new and existing
new floor at the juncture.
e. Doweled joints. The primary function of dow-
floors for the following conditions:
(a) When load-transfer devices (keyways
els in floor slabs is that of a load-transfer device. As
or dowels) or a thickened edge was not provided at
such, the dowels affect a reduction in the critical
the free edge of the existing floor.
edge stress directly proportional to the degree of
(b) When load-transfer devices or a thick-
load transfer achieved at the joint. A secondary
ened edge was provided at the free edge of the
function of dowels is to maintain the vertical
existing floor, but neither met the design
alignment of adjacent slabs, thereby preventing
requirements for the new floor.
faulting at the joints. Dowels are required at all
(c) For transverse contraction joints, when
contraction joints in slabs that are 8 inches or
removing and replacing slabs in an existing floor.
greater in thickness and for thinner slabs in
(d) For longitudinal construction joints,
concentrated traffic areas.
(1) Dowel specifications. Dowel diameter,
when removing and replacing slabs in an existing
floor if the existing load-transfer devices are
length, and spacing should be in accordance with the
damaged during the slab removal.
criteria presented in table 5-3. When dowels larger
(e) Any other location where it is
than 1 inch in diameter are required, an extra-
necessary to provide load transfer for the existing
strength pipe may be used as an alternate for solid
floor. The special joint design may not be required
bars. When an extra-strength pipe is used for
if a new floor joins an existing floor that is grossly
dowels, however, the pipe should be filled with a
inadequate to carry the design load of the new floor,
stiff mixture of sand-asphalt or cement mortar, or
or if the existing floor is in poor structural
the ends of the pipe should be plugged. If the ends
condition. If the existing floor can carry a load that
of the pipe are plugged, plugs should fit inside the
is 75 percent or less of the new floor design load,
pipe and be cut off flush with the end of the pipe so
special efforts to provide edge support for the
that there will be no protruding material to bond
existing floor may be omitted; however, if omitted,
with the concrete and prevent free movement of the
accelerated failures in the existing floor may be
pavement. All dowels should be straight, smooth,
experienced. Any load-transfer devices in the
and free from burrs at the ends. One-half of each
existing floor should be used at the juncture to
dowel should be painted and oiled or otherwise
provide as much support as possible to the existing
treated to prevent bonding with the concrete. A
floor. The new floor will simply be designed with a
schematic drawing of joint layout showing dowels
thickened edge at the juncture. Drilling and grouting
is given in figure 5-14.
dowels in the existing floor for edge support may be
5-22
Previous Page
