LOADS.

The loads to be considered in designing highway bridges and trestles are the following; and all parts of same are to be proportioned to sustain properly the greatest stresses produced thereby for all possible combinations of the various loads, excepting only that the live load and wind load cannot act together, unless the structure carry an electric railway; for the reason that no person would venture on the bridge when even one half of the assumed wind-pressure is acting.

  A. Live Load.

  B. Impact Allowance Load.

  C. Dead Load.

  D. Direct Wind Load.

  E. Indirect Wind Load or Transferred Load.

  F. Effects of Changes of Temperature.

When a highway bridge carries an electric railway, it shall be proportioned also for

  G. Traction Load, and,

  H. Centrifugal Load.

In calculating the stresses caused by a uniform moving load, the load shall be assumed to cover the panel in advance of the panel point considered; but the half-panel load going to the forward panel point will be ignored; or, in other words, the uniform load will be treated as if concentrated at the various panel points.

LIVE LOADS.

The uniformly distributed live loads per square foot of floor, including the entire clear widths of both main roadway and footwalks, shall be taken from the curve diagram shown on Plate V.

In applying these curves the span lengths used shall be as follows:

For stringers and joists, a single panel length; for floorbeams and single panel suspenders with their corresponding primary-truss struts, two (2) panel lengths;  for hip verticals