The New York Rapid-transit Subway

Proceedings.] PARSONS ON NEW YORK RAPID-TRANSIT SUBWAY. 23 column became the vertical end stiffeners of the cross girder. The projecting webs of the girders were sheared to a curve and stiffened on the edges by angles. This formed a cross structure as near a unit as it is possible to make of riveted members, and consequently gave the maximum stiffness. This design of column not only has the merit of maximum stiff- ness for the erected structure, but it is economical in construction, requiring but two rows of rivets; has all its parts exposed for inspection and painting ; and, being smooth on the sides and without lattice bars, prevents mischievous boys from climbing from the street to the structure above. The expansion-joints in such a structure are usually sources of trouble, especially if they consist of any kind of pocket or shelf in which dirt may find lodgment. The joint employed in the elevated structures of the railway consisted of a vertical bracket riveted to the web of the transverse girder, on which was placed a half pin 4 inches in diameter, on which rested a projecting bracket riveted to the web of the longitudinal girder. The ends of the pins were then covered with lug angles to prevent lateral movement of the pins or accumu- lation of dirt. These joints were introduced at every third or fourth panel. The details are shown in Figs. 12, Plate 6. The symmetry of the structure was preserved by placing brackets at the end of the movable girder with slotted holes in their top angles to correspond with the stiffening-brackets riveted to the cross girders and the longitudinal girders at bents other than those with expansion- joints. The only structure of special magnitude on the elevated portion is an arch with a span of 168'5 feet, carrying the railway and a station, at a height of 50 feet, over the diagonal crossing of two very wide streets occupied in the centre by a complicated crossing at the junction of two double-track tramways, which prohibited the use of any vertical supports. The street followed by the railway is on a decided gradient, so that the arch has a difference of 5 feet in elevation at the springings. A parabolic two-hinged arch was adopted, with three ribs spaced 24 feet 3 inches apart. The foundations of the arch are concrete piers carried to rock, and of sufficient length to contain witliin the foundations the resultant line of thrust of the arch and the vertical load transmitted by the first row of columns. The skewbacks are composed of granite blocks. The general design of the arch and details of the end bearing are shown in Figs. 14 and 15, Plate 6. All the elevated portions were designed to carry a train of motor- cars, each of whicli had an extreme length of 46 feet, witli a total