276
HISTORY OF ENGINEERING.
Book f.
Fig. 284. BRIDGB OP FROUART.
Bridge of Rouen , on the Seine : the remains of a stone bridge built by Matilda, wife ofHenry II. , Duke of Normandy and King of England, about 1160, are still visible atRouen . It was 480 feet long, and composed of thirteen arches ; several of these havingfallen, and others carried away, the thoroughfare was closed in 1564, and in 1626 it wasreplaced by a bridge of boats.
The new bridge was decided upon in 1810. The designs were made by M. Lemasson,and the work begun in 1811. In 1812, it was placed under the direction of M. Lamande,who proposed several changes, the chief of which related to the manner of founding thepiers.
It consists of two equal parts, which may be considered as two distinct bridges, separatedby a circular mass which forms the lower extremity of the island of La Croix. They arenot in a line with each other, their axes comprising an angle of 146°, which arrangementwas adopted in order that the two bridges might be perpendicular to the current ofthe two arms of the river, and directed to the points of commencement of the two newroads.
Each bridge consists of three segmental arches. The span of the middle one is 101feet 8 inches, and the versed sine of the arc of the intrados 13 feet 9 inches. The span ofthe lateral arches is 8o feet 3 inches, and their versed sine 10 feet 7 inches. The spandrilsare decorated by a semicircular niche, placed over each pier. The springings arc 16 feet
9 inches above low water. The thickness of the arches 3 feet 5 inches. The piers, ter-minated by semicircular starlings, are 10 feet 5 inches thick at the springings, and 11 feet
10 inches at the base. The width of the iowest course of footings is 16 feet 8 inches; thepiles which support it are cut off 9 feet 9 inches below low water. The abutments areformed by a mass 59 feet thick and 60 feet 9 inches wide, in the middle of which an arch isconstructed, 13 feet span, and 12 feet 4 inches high to the key-stone. This mass was foundedon piles 3 feet 6 inches below the surface. 'Die cornice on each side has a fall of 1 in34 from the middle of each bridge, which slope extends to the approaches. Thetotal width is 49 feet 2 inches, of which 29 feet 6 inches is for the roadway and 7 feet10 inches for each foot pavement. The embankment required was nearly 16 feet in depth,and extended to the houses.
The abutments were founded by cofferdams, on piles 39 feet 4 inches long, 4 feet 3 inchesapart: they are defended by a row of piles touching each other. The depth at low wateris 28 feet 6 inches, and the side rises about 6 feet 6 inches. Die piers were founded bycaisscons on piles 49 feet 2 inches long, and 3 feet 3 inches apart.
The foundation is surrounded by a row of piles touching each other, retained by bands ;it is farther strengthened by a similar row 5 feet 2 inches wide, forming a starling roundthe piers, the heads of which are 19 feet 8 inches below low water. The interior both ofthe piers and the starling was dredged, and filled with concrete, and the exterior defendedby rubble work.
The arches w’ere placed on fixed centres formed by three pairs of principals, supportedby two rows of piles.
Bridge of Sevtcs, over the Seine, on the road from Paris to Versailles, was designed by