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BENDING ON TOP CHORDS.
See Specifications for Railroad Structures.
BENDING ON INCLINED END POSTS.
The Specifications for Railroad Structures under this heading are to be followed, with this exception: in bridges that do not carry trains, the live load and the wind load are assumed not to act simultaneously.
BENDING DUE TO WEIGHT OF MEMBER.
See Specifications for Railroad Structures.
GENERAL LIMITS IN DESIGNING.
The following general limits shall be adhered to in designing highway bridges and viaducts:
The perpendicular distance between central planes of trusses shall never be less than one twentieth (1/20) of the span.
The length of any bracket cantilevered beyond a truss or girder shall never exceed one half of the perpendicular distance between the central planes of adjacent trusses or girders, unless there be more than two trusses to the span.
No metal less than five sixteenths (5/16) of an inch in thickness shall be used, except for filling-plates; and in important bridges this limit shall be increased to three eighths (3/8) of an inch.
The least allowable thicknesses of webs of rolled I beams shall be as follows: |