A Treatise On The Principles And Practice Of Dock Engineering

IRON COLUMNAR PIERS. 289 projection of 7 feet at the outer extremity, forming a support to a stairway. fhe columns are arranged in parallel rows of five, the middle columns being 7 feet 10| inches apart and the outer ones 5 feet 3 inches. They are 5 inches in diameter, connected by 3-incli by 3-inch by ^-inch angle-iron bracing. The deck is planked upon whole timber bearers, at a height of 14 feet above the water level. Scales. °JJ.l I £ ? 7 9 ? 10 Metres. 0 3 10 20 30 Feet Fig. 228. —Jetty at Zeebrugge. In order to allow freedom of movement to the littoral current a portion, 440 yards long, of the jetty or mole at Zeebrugge, on the North Sea, is constructed of mild steel in openwork. The structure (figs. 227 and 228) is composed of 80 bays of 16j feet each, and is carried by parallel rows of piles or columns, six in number, of which four support a double line of rails and two the side extremities of the platform. The heads of the piles are connected by a lattice girder, and at low-water level, there is a second horizontal mem- ber formed of two channel irons. The diagonal bracing is 2 inches in diameter, fitted with tightening- up shackles. Each column is formed of four quadrant irons, rivetted together at their longitudinal flanges. The internal diameter is 9^ inches and the thickness I inch. The sectional area of each pile is about 31 square inches. At the foot of each pile is a wooden shoe, 16 inches in diameter and a yard long, bearing against a collar on the pile. The rows of piles are connected longitudinally by plate girders, four of which are 2 feet 6 inches deep and the outer two 2 feet deep, witli inch by J-inch flat-bar wind bracing. The decking comprises ö-inch by dj-inch oak joists, set 1} inches apart clear, to allow a passage for waves. The cover-plates in the railways are of cast iron, pierced pattern. On the outer face of the jetty, there is a plate superstructure, 15 feet inches in height, suitably stiffened, to afford shelter to trains. This superstructure carries a gangway for pedestrians. An interesting example of a jetty of a somewhat unusual type for iron, I ough not for wood, is given in figs. 229 and 230, which is a section of one constructed at the port of Touapsé, on the Black Sea, in 1896-97. The jetty is 800 feet long and has two inclined faces, each formed of a row of ilway metals on end, driven into the ground some 10 inches apart, being ouided and strengthened by two rows of longitudinals ; the upper, 9 feet 19