the vertical bracing and to the ends of the span by the upper lateral system.

In important bridges, suspenders or hip verticals and two or more panel lengths of bottom chord at each end of span shall, preferably, be made rigid members, except that eye-bars are to be used for bottom chords of "A" truss bridges.

All floor-beams are to be riveted to the truss-posts in truss-spans, excepting in the case that eye-bars be used for suspenders or hip verticals. In such cases floor-beam hangers may be used, provided they be made of plates or shapes, and that they be stayed at their upper ends against all possibility of rotation.

CONTINUOUS SPANS.

See Specifications for Railroad Structures.

TRESTLE-TOWERS.

In general, the descriptive specifications for railroad trestles are to be followed in designing highway trestles or viaducts, except that in cheap structures all sway-diagonals of towers maybe made of adjustable rods, with horizontal struts at the panel points, provided that the struts be rigidly riveted to the columns.

CAMBER.

All trusses must be provided with such a camber that, with the heaviest live load on the span, the total camber shall never be quite taken out by deflection. With parallel chords, sufficient camber will be obtained by making the top-chord sections longer than the corresponding bottom-chord sections by five thirty-seconds (5/32) of an inch for each ten (10) feet of length.

Plate girders and shallow, open-webbed, riveted girders should not be given any camber.

EXPANSION, ANCHORAGE, AND NAME PLATES.

See Specifications for Railroad Structures.