STANDARD RULES FOR BRIDGE MASONRY CONSTRUCTION The following are outline rules and specifica tions for the design and construction of bridge masonry, similar to those in use by the large railroads of the United States at the present day. They are intended to cover only the main features: General Rules for Masonry Plans Scale. In general, masonry plans should be made to a scale of about 1/4 inch =1 foot. Details may be drawn to larger scale, and scale should be noted.
Views. As many views should be given as will show the construction of every piece of masonry. In structures which consist of several parts, a diagram should be added showing the relative location and elevation of the dif ferent parts.
Dimensions. Dimensions of masonry structures should not be given closer than to quarters of an inch, except the vertical dimensions locating bridge-seats, which should be given to eighths.
Only such dimensions as are necessary for laying out the work in the field or as assist materially in checking the plan, should be noted on drawings. Repetition of dimensions should be avoided.
All corners of footing courses and neatwork lines on footings should be definitely located. All intersections of planes should be definitely located.
Exact batters on inclined faces, as well as determin ing dimensions, should be given.
All dimensions should be referenced to some definite base line and working point, as the center-line of track or the center-line of structure and their intersection. In skew bridges the center-line of structure should be used.
Piles should be located in rows, the spacing being given perpendicular and parallel to the rows, and the end pile in each row being definitely located.
Elevations and distance from base of rail of all im portant points in masonry structures, should be given on plans.
General. The directions of the compass are to be taken as given in the time-table—going to Chicago being East and away from Chicago being West. East should always be at the right-hand side or top of the drawing.
The directions of the compass should be noted on all drawings.
High-water and low-water and low-steel should be shown to scale, and marked with elevations on substruc ture plans.
All masonry plans should contain the following infor mation under the heading "General Notes": Location of structure; Drawing number of survey; Bench-mark; Present elevation base of rail at Sta. .... ; Proposed elevation base of rail at Sta. .... ; Station .... at East end of present bridge; Grade .... rising .... ; Alignment; Super-elevation; High-water elevation; Low-water elevation; Bearing on soil; Bearing on piles; Falsework ; Drawing number of steelwork.
All masonry plans should contain a bill of material to include cubic yards of concrete, number, size, and length of reinforcing bars, piles, drain-pipes, etc.
Titles of masonry plans on each sheet should give size of span, character and location of structure, and sub title for that particular sheet.
When there are several sheets to one set of plans, each sheet should be numbered just above the title as two or five, or as the case may be.
Notes on Foundations Loads on Foundations. The recommendation of the Assistant Engineer regarding the allowable bearing on soil or allowable load on piles, should be followed in the design of foundations.
In case there is no recommendation, the bearing is to be based on the data given on the survey. The following limiting values will serve as a guide: Rock 10 to 100 tons per sq. ft.
Gravel 3 to 6 tons per sq. ft.
Sand 1 to 4 tons per sq. ft.
Clay 1 to 3 tons per sq. ft.
Mud, loam, gumbo...1/2 to tons per sq. ft.
In the absence of recommendation regarding load on piles, 13 tons per pile should not be exceeded.
Proportions of Foundations. The on foundations should be kept the same under all parts of continuous structures. Foundations should be designed to distribute the loads upon them uniformly.
In general, footings for natural foundations should be made 1 ft. 6 in. or 2 ft. thick.