The Viaduct Works' Handbook
Forfatter: Henry N. Maynard
År: 1868
Forlag: E. And F. N. Spon
Sted: London
Sider: 108
UDK: 624.3
Being A Collection Of Examples From Actual Practice Of Viaducts, Bridges, Roofs, And Other Structures In Iron; Together With Tables Of Prices, Weights, And Other Information Useful To Engineers In Design And Estimating Wrought And Cast-Iron Work
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12
Tagus Bridge.—This bridge, erected at Villa Nova da Con-
stancia, on second section Badajoz line, is an example of the class
Fig. 2, selected from many others of the same. It consists of
16 spans of 101 feet 10 inches each from centre to centre of piers,
and the superstructure, that is to say, the girders and floor without
piers, is constructed for a single line of railway, so that an additional
line can be added by the addition of more girders.
The main girders, of which there are two for each span for
a single line of railway, are 8 feet 103 inches deep, placed about
10 feet apart, centre to centre, and coimected together in pairs by
light horizontal bracing. Their compression bars are of the semi-
rectangular tube section, 18 inches wide on top, and 7 inches deep,
giving a sectional area of 24’75 square inches at centre, and the
greatest strain is 4 tons per sectional inch. This area is gradually
diminished from the centre to the ends, where it is but 9 square
inches. The tension bars consist of four bars 9 inches by §ths of
an inch, and, at the end, two bars 9 inches by | an inch. Those of
the diagonals acting as struts are made of bar and angle iron, those
acting as ties of flat bars. The end strut consists of one flat bar
6 inches by ths of an inch, and two angle bars 4 inches by 3 inches
by ths of an inch, and the end tie of two bars 6 inches by §ths of
an inch ; the centre struts and ties are of lighter sections. The floor
is supported by transverse girders 19 in each span, placed about
5 feet 6 inches apart, resting on top of the main girders and attached
thereto by bolts. These girders are composed of -inch plate
9 inches deep, and four angle irons 3 inches by 3 inches, and are
made long enough to give clear 14-feet width of roadway when
the handrail standards are fixed upon them. The ends of the main
girders, to allow for expansion, rest upon iron rollers moving on
bed plates attached to tops of the piers. The weight of ironwork
per span for a single line of way is as follows :—
, Tons.cwts.qrs. lbs.
Iwo compression bars ...................................8 4 2 8
Two tension bars .......................................5 19 3 0
Two sets of struts and ties ...........................6 10 3 13
Four vertical ends ....................................1 13 1 6
Total for two main girders.
22 8 132