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SECTION 3
OPERATION
Section 3
Placing Screed Rail & Paving Forms
•
The set-up is what determines the longitudinal profile
of your roadway paving or bridge deck surface .
• There are two screed rail setups for bridges . The
engineer or DOT specifications will determine if the
BDF will ride on the pipe located on the edge forms or
on the pipe located on the bridge girders .
FIRST TYPE OF BRIDGE DECK SET-UP:
- Look at the type and spacing of the overhang
brackets if the machine is riding on forms and
refer to the manufacturer’s specifications for size
of overhang brackets and spacing .
Consult with
the factory about your machine weight and
wheel loads.
- Once the BDF loads have been determined, THIS
will dictate placement of the Screed Rail .
- The Rail position must be accurate and conform
to the grade required . Allen Engineering
recommends 2-inch schedule 80 pipe with a
sleeve at one end to connect two sections of pipe
together .
- 24 inches on center is the recommended spacing
for the screed chairs . (Special situations may
have a maximum 30 inches).
- The rails and chairs should be double checked
after placing the machine on the deck .
- After the BDF has been set on the deck, it will
need to run up and down to take out any timber
crunch or settling of the form work .
- Double check the form-work again .
SECOND TYPE OF BRIDGE DECK SET-UP:
- When the machine is riding on bridge girders you
will need to fabricate
a screed chair stand
that will be epoxied or
welded to the beam
or a girder plate (SEE
PICTURE 7)
- We recommend you tie
the vertical tube to the rebar mats for stability .
- The top of the vertical tube will be below the
finished surface grade.
- The screed rail needs to be adjusted to
conform to the longitudinal profile which can be
accomplished in various ways .
- A folding ruler or tape measure with the use of a
level can be used to determine the quarter points
on the deck to the top of the screed rail .
- Pulling a string-line between the 2 points or
measuring from the grade-line on the form to
the top of the screed pipe to set the grade of the
pipe .
- Remember this is just an initial setup at this
time and the rails and chairs should be double
checked after placing the machine on the deck .
- Double check the form-work again .
PAVING FORM SET UP:
• A strong solid sub-base is required for all concrete
paving forms to sit on to prevent the paving forms from
sinking into the sub-grade causing an improper grade
profile.
• Allen recommends our Steel Forms or forms designed
and engineered to carry the weight and load of the
paver. The BDF will be outfitted with flat flange poly-
bogie wheels with a 3-inch width to ride on the top of
the paving form .
PICTURE 7
The screed, pipe rail, and
concrete paving forms provide the
longitudinal profile of the paving
surface and the proper set-up is as
equally important as the machine
operation.
Screed Chair
Screed Chair
Stand