Provided that wooden shims be bolted to the top flanges for spiking the planks thereto, no sway-bracing will be required; but otherwise it must be used. Each I beam is to have at each end a pair of stiffening angles, fitting tightly at both top and bottom to the flanges, to carry the load to the masonry and to form part of the end bracing-frames. Each pair of girders is to have a bracing-frame at each end; and under each end of each I beam there is to be riveted a bearing-plate of proper area and thickness (never less than five eighths [5/8] inch) to distribute the load uniformly over the masonry, said plate being bolted effectively to the latter, with due provision for expansion and contraction.

DETAILS OF DESIGN FOR PLATE-GIRDER SPANS.

In designing plate-girder spans for highway structures, the corresponding specifications for railroad structures are to be followed, except that the depths of girders shall preferably be not less than one twelfth (1/12) of their span, that metal five-sixteenths (5/16) inch thick may be used, and that the stiffening angles may be made as small as two and a half (2 1/2) by two and a half (2 1/2) inches.

DETAILS OF DESIGN FOR OPEN-WEBBED, RIVETED
GIRDER SPANS.

See Specifications for Railroad Structures.

DETAILS OF DESIGN FOR PIN-CONNECTED SPANS.

The sections of top chords and inclined end posts of through-spans shall consist, generally, of two rolled or built channels and a single cover-plate. In the case of built channels, the section of the member must be so proportioned as to bring its centre of gravity as near as possible to the middle of the webs.

Main vertical posts shall generally be composed of two laced channels, preferably rolled ones, although built channels may be used where large sections are required.