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STATE GEOLOGIST. 163 
ribs placed in the bridge. The whole arch is 38 inches thick at the 
crown and 70 inches near the haunch. The water is about 6 feet deep 
where the bridge stands and has a velocity of nearly 30 miles per hour. 
The bridge cost $102,070.00. Figure 99 shows the bridge. 
Oconomowoc, Wisconsin.—A very neat concrete bridge was built 
in 1899 for Mr, P. D. Armour, Jr., at his summer residence near Ocono- 
mowoc, Wisconsin.* It has a span of 21 feet, a rise of 6 2-3 feet, and 
width of 15 feet. The arch is 5 inches thick, reinforved by three ribs 
2 feet wide and 4 inches thick> A pair of flat iron bars, 34 inch by 3% 
inches, is placed at either side of the bridge conforming to the arch. These 
are latticed together forming steel trusses, the bottom of which are con- 
nected across the bridge by % inch round iron rods spaced 18 inches apart 
and % inch above the face of the concrete. Number 16 expanded metal, 
2% inch mesh, was laid over these rods. The concrete, composed of 
I part cement, 3 parts torpedo gravel and 4 parts of 34 inch limestone, 
was then tamped in place. The surface coat was composed of 1 part 
cement, I part granite screenings and 1 part torpedo gravel. ‘The facing 
is I inch thick and was spread upon the form before the concrete was 
laid. The centering was removed in nine days and heavy loads were 
hauled over the bridge. Figure 100 illustrates the beauty of the bridge. 
Chatellerault Bridge, Vienne, France.—The Hennebique system of 
steel concrete is well illustrated in the construction of the Chatellerault 
— ~ al 
a TPE ee eg 309 je mas 
Be IP Nae 
73 . x att 
Fig. 101.—A Cross Section of a Bridge Showing Hennebique System. 
bridge in France. ‘This bridge has three spans, two of 131 feet and the 
other 164 feet in length. It was given several severe tests and records 
were taken of the deflections. A moving load consisting of road rollers and 
heavily loaded wagons, altogether equal in weight to 308,000 pounds, 
was driven across the bridge. These loads were again driven across after 
large wooden strips had been placed in the roadway in order to produce 
a series of shocks or blows. The maximum deflection upon the two 
shorter spans-was 6 mm., and. for the center arch 10 mm., or slightly 
*Hngineering News, Vol 42, P. 250. 
