RULES FOR ORDERING MATERIALS. 416 



joints should be so arrange. I th.it the rivets connecting the fixed span to the croaa girder can be 

 <lri\vn alt. i tin- c\pan,i.m span is in place. In viaducts, etc., two spans, abutting on a bent, 

 >h<.ul(I be so arranged that cither span ran be set in place entirely independent of the other. The 

 same thing applies to uinler spans of different depth resting on the same bent. Holes for anchor- 

 holts should be so arranged that the holes in the masonry can be drilled and the bolts put in place 

 after the structure has been erected complete. 



In structures consisting of more than one span a separate bed-plate should be provided for 

 each shoe. This is particularly important where an old structure is to be replaced; if two shoes 

 were put on one bed plate or two spans connected on the same pin, it would necessitate removing 

 two old spans in order to erect one new one. In pin-connected spans the section of top chords 

 t the center should be made with at least two pin-holes. In skew spans the chord splices 

 should be so located that two opposite panels can be erected without moving the traveler. Tie 

 plates should be kept far enough away from the joints and enough rivets should be countersunk 

 inside the chord to allow eye-bars and other members being easily set in place. Posts with 

 channels or angles turned out and notched at the ends should be avoided whenever possible. 



ORDERING MATERIAL. Bridge Work. Ordinarily plates less than 48 in. wide are 

 ordered U. M. (universal mill or edge plates), but when there is no need for milled edges and 

 prompt delivery is essential specify either U. M. or sheared. Never order widths in eighths. 

 Flats and universal (edge) plates over 4 in. in width should be ordered in- even inches, flats under 

 4 in. should be ordered by i in. variation in width. Flats J in. and under in thickness are very 

 difficult to secure from the mills and should be avoided if possible. 



Rolling mills are allowed a variation of J in. in width of plates, over or under, and a variation 

 of | in. in length, over or under, from the ordered width or length. Rolling mills are allowed a 

 v.iri.ition of $ in. over or under the ordered length of beams, channels, angles, zees, etc. An 

 extra price is charged for cutting to exact length. See Chapter XIII. 



Allow ^s in. in thickness for planing plates 2 ft. 6 in. square or less, J in. for plates more than 

 2 ft. 6 in. square, and j; in. for columns; chords and girders which have milled ends are ordered 

 1 in. longer than the finished dimensions. 



Web plates should be ordered i in. less than the back to back of flange angles unless a less 

 clearance is specified. Web plates should preferably be ordered in even inches and the distance 

 back to back of angles made in fractions. 



When angles, beams or channels are bent in a circle allow 9 in. to 12 in. for bending. 



Bent plates should be ordered to the length of the outside of the bend. 



out_to oyt___ 

 FIG. 24. BEAMS BETWEEN COLUMNS. 



Large gusset plates, large plates with angle cuts, etc., should be ordered as sketch plates, 

 when the amount of waste if ordered rectangular will exceed 20 per cent. Mills will not make re- 

 entrant cuts in plates or shapes. 



In ordering lacing bars add A i n - to the finished length and order in multiple lengths. 



ORDERING MATERIAL. Building Work. Order beams in foundation neat length. 



Order beams framing into beams f in. short for each end, see Fig. 24. 



