In proportioning the flanges of plate girders, one eighth (1/8) of the gross area of the web is to be assumed as concentrated at the centre of gravity of each flange; or, in other words, after having found the net sectional area required for the tension-flange by ignoring the resistance of the web to bending, there is to be subtracted therefrom one eighth (1/8) of the gross area of the web-plate.

At the ends of all plate girders there must be sufficient rivets in each flange to transfer properly thereto from the web the total end-shear in a distance equal to the effective depth of the girder.

At the ends of cover-plates the spacing of the rivets which attach the covers, for a length equal to at least twice the width thereof, shall be made the minimum used in the flanges.

Under each end of each plate girder there is to be riveted a bearing plate of proper area and thickness and thoroughly stiffened so as 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 OPEN-WEBBED, RIVETED
GIRDER-SPANS.

All open-webbed, riveted girders for both deck and half-through bridges shall be riveted up completely in the shop, as field-riveting will be allowed only for the lateral bracing, except in structures for foreign countries.

In open-webbed, through, riveted girders, however, the connection of main members will have to be by field-rivets. In such cases all of the truss-members will have to be assembled in the shop, after which the rivet-holes for the connections shall be reamed so as to ensure perfect fitting in the field.

The use of shallow open-webbed, riveted girders shall be avoided whenever possible, for the reason that they are quite as expensive and never as satisfactory as plate girders. In case, though, of their being required, as for instance in elevated railroads occupying city streets, they are to be provided with short, substantial web-plates at the ends and at all intermediate points where connections are made to other girders.