2, Plate LXII) was erected to
the height of the underside of the I-beam ties, the posts being footed
in holes, about 3 in. deep, left in the concrete floor to prevent
slipping. In the open-cut sections the sand-wall forms were of undressed
plank tacked to the studding and braced from the trestle; in the tunnel
section they were spiked to the face of the posts supporting the
timbering.
The side-wall forms were made up in panels about 3 by 10 ft., and were
clamped to studs by U-shaped irons passing around the stud and bolted to
the cleats on the back of the panels, the studs being braced from the
trestle. The side-wall concrete was deposited in three sections. The
first was brought up just above the sidewalk and formed the bench for
the high-tension ducts; the second carried the wall up to the springing
line. Before placing the third section the I-beam ties were set in
position (Fig. 3, Plate LXII) on top of the trestle, and the reinforcing
rods in the haunch of the arch were hung from them. The concrete was
carried up to a skewback for the arch, as shown in the brick-roof
cross-section (Plate XII) and embedded the ends of the ties.
The centers for the arches stood on the I-beam ties, and the tops of the
hangers, for the permanent support of the ties near their center, were
inserted through the lagging.
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