the flange angles. These must be long enough to develop by the connecting rivets at least twenty-five (25) per cent more than the full strength of their net section.

Splices in flange-plates and angles must always be avoided when sufficiently long plates and angles are procurable, which will always be the case, unless the span be abnormally long. Where flange-splices are unavoidable, they must be so located that no two pieces of either the flange or the web shall be spliced within two (2) feet of each other, and so that no flange-splice shall occur at any point where there is not an excess of sectional area above the theoretical requirements. Every non-continuous flange-piece shall be fully spliced so that the splicing plates and rivets shall have a calculated strength at least twenty-five (25) per cent greater than that of the section spliced. Field-splicing of plate girders will never be allowed for fixed spans, except in structures for foreign countries.

At least one half of every flange section must consist of angles, or else the heaviest sections of the latter must be used; and the number of cover-plates must be made as small as practicable, in no case exceeding three (3) per flange. The lengths of these cover-plates must be such as to make them project at each end not less than nine (9) inches beyond the point determined by the calculations for the requisite resistance to bending.

Where two or three cover-plates per flange are used, they shall be of equal thickness, or shall decrease in thickness outward from the angles. The cover-plates shall not extend more than four (4) inches or eight (8) times the thickness of the outer plate beyond the outer line of rivets. With cover-plates more than fourteen (14) inches wide, four (4) lines of rivets shall be used.

The compression-flanges of plate girders shall be made of the same gross section as the tension-flanges; and they shall be so stiffened laterally that the unsupported length shall never exceed twelve (12) times the width of flange.

In deck-spans there are to be bracing frames at the ends and at intermediate points not more than fifteen (15) feet apart; and there is to be an  effective  system of diagonal bracing of