We give engravings of the viaduct over the river Retiro, Brazil, our
illustrations being reproduced by permission from the Proceedings of the
Institution of Civil Engineers. In a "selected paper" contributed to the
volume of these proceedings just published, Mr. Jorge Rademaker Grunewald,
Memb. Inst. C.E., describes the work as follows:
[Illustration: VIADUCT OVER THE RETIRO, BRAZIL.]
This viaduct was constructed in the year 1875, according to designs
furnished by the author, for the purpose of passing the Dom Pedro Segundo
State Railway over the valley which forms the bed of the river Retiro, a
small confluent on the left bank of the river Parahybuna. It is 265
kilometers (165 miles) from Rio de Janeiro, and about 10 kilometers (6.4
miles) from the city of Juiz de Fora, in the province of Minas Geraes,
Brazil. It has a curve of 382 meters (1,253 ft.) radius, and a gradient of
1 in 83.3. Its total length is 109 meters (357 ft. 7 in.); width between
handrails, 4 meters (13 ft.); and greatest height above the bed of the
river, 20 meters (65 ft. 7 in.).
The viaduct is composed of seven semicircular arches, each end arch being
built of ashlar masonry, and of 6 meters (19 ft. 8 in.) diameter; five
intermediate arches, 15 meters (49 ft. 2 in.) in diameter, are of iron. The
four central piers are of iron erected on pillars of ashlar masonry. The
metallic part of this viaduct is 80 meters (262 ft. 6 in.) long, and is
constructed in the following manner: The arches, and the longitudinal
girders which they support, are made of two Barlow rails riveted together,
with an iron plate ½ inch thick placed between them. The spandrels are
formed of uprights and diagonals, the former being made of four
angle-irons, and the latter of one angle-iron. Each pair of arches,
longitudinal girders and uprights, is transversely 3 meters (9 ft. 10 in.)
from center to center, and is connected by cross and diagonal bracing. On
the top of the longitudinal girders are fixed cross pieces of single Barlow
rails, upon which again are fastened two longitudinals of wood 12 in.
square in section, and which in their turn carry the rails of the permanent
way.
The gauge of the Dom Pedro Segundo Railway is 1.60 meters, or 5 ft. 3 in.
nearly, between the rails. At each end of the transverse Barlow rails is
fixed the customary simple iron handrail, carried by light cast-iron
standards. The iron piers are each formed of four columns, and the columns
consist of two Barlow rails, with a slotted iron plate ½ inch thick let in
between the rails, and the whole being riveted together connects each pair
of side columns.
The details show the system of cross and diagonal bracing. The columns are
each supported by four buttresses formed of plates and angle-irons. These
buttresses, fastened with bolts 8 ft. 3 in. long, let into the masonry
pillars, secure the stability of the viaduct against lateral strains, due
mostly to the centrifugal force caused by the passage of the trains.
The Barlow rails, which constitute the peculiarity of the structure, are
from those taken up from the permanent way when the Vignoles pattern of
rail was adopted on this railway. The whole of the foundations were built
without difficulty. The principal parts of the iron work were calculated to
resist the strains resulting from a weight of 4 tons 8 cwt. per lineal
meter traveling over the viaduct at a velocity of 60 kilometers, or about
37 miles, per hour.
In spite of its fragile appearance this viaduct has, up to the present
time, served in a most satisfactory manner the purpose for which it was
built.--_Engineering_.
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