INSTRUCTIONS FOR THE DESIGN OF RAILWAY BRIDGES.* 



The following instructions for the design of the details of railway bridges have been prepared 

 y the engineering department of the Chicago, Milwaukee & St. Paul Railway, 1912. 



RIVETS AND RIVET SPACING. I. For conventional signs, actual sizes of heads and 

 of field rivets for various grips, see Fig. 10, Chap. XII, and Table 109, Part II. 



2. Size. Rivets for steel bridge work shall usually be \ in. diameter, except where limited 

 y si/i- of m.iti-rial. In very heavy work, where rivets of long grip are required, such as in the 

 ruins of draw spans, I in. rivets are preferable. 



3. Flattened. Rivet heads are not to be flattened to less than f in. high. 



4. Countersunk. Where heads less than | in. high are required, they shall be countersunk. 

 'lu- conventional signs for countersunk rivets mean that rivets shall be countersunk and chipped. 

 Vhrre chipping is not required, it should be so noted on the drawing. Countersunk rivets should 



whenever possible. 



5. Clearance of Heads. In determining clearance the heights of heads should be assumed 

 jws: 



Full head j in. rivet Jin. high 



Full head 1 in. rivet | in. high 



Full head f in. rivet A in- high 



Head flattened to f in. rivet \ in. high 



Countersunk, not chipped i in. high 



6. Spacing. In spacing rivets the use of fractions smaller than J in. should be avoided, 

 unavoidable, locate in such a way as to cause the least number of repetitions. 



Locate splices and stiffeners with a view to keeping the rivet spacing as regular as possible. 



7. Stagger and Clearance. For distances center to center of staggered rivets and clearance 

 jired for driving, see standards. In special cases where the prescribed clearances are im- 

 sible, allow at least \ in. clearance for f in. and I in. rivets and A in. for f in. rivets, from the 



of the rivet head to the nearest surface or other obstruction. 



In the connection of cross-frames to girders, and in small lug angles and detail angles, rivets 

 be spaced so that they will not interfere with each other in driving. 



In girder flange angles, the rivets in the "flange" legs should stagger at least I in. with rivets 

 he "web" legs, but should be staggered uniformly. 



RIVETED CONNECTIONS. i. Grouping. Rivets should be grouped to insure that 

 line of applied stress passes as near as possible through the center of the group of rivets which 

 that stress. Where the eccentricity is marked, the stress on the extreme rivet due to this 



itricity shall be computed and when properly combined with the direct stress shall not exceed 

 illdwable stress per rivet. 



2. Gusset Plates. Gusset plates shall have such a thickness as will on any section develop, 

 ;nding and shear, the full stress which has been transmitted to it by the rivets outside the 

 ML. 



3. Clearance. The clearance between chords and web members entering same and other 

 ir riveted connections shall be not less than f in. in heavy structures and tV m - m light 

 tures. 



PINS AND PIN PACKING. i. Pins. Pins shall be proportioned to carry the reactions 

 he stresses in all the members meeting at a point at unit stresses specified. In computing 

 ling moment on pins, assume each load concentrated at its center of bearing. 

 2. Pin Packing. Observe the following rules regarding arrangement of eye-bars and pin 

 s: 



(1) Arrange pin packing so as to reduce bending moment on pin to minimum. 



(2) Leave at least ^g in. clearance between adjacent surfaces. 



(3) Provide an additional clearance in the length of the pin of not less than \ in. 



(4) When two or more pin plates are riveted together, allow fa in. for each plate, in addition 

 J its nominal thickness. 



(5) Where hinge plates are used allow | in. clearance between hinge plates and faces of con- 

 ecting members. 



(6) Adjacent surfaces of eye-bars composing a member shall have a clearance of f in. to 

 How for painting. 



(7) All eye-bars are to lie in planes as nearly as possible parallel to the center line of truss, 

 10 divergence exceeding one inch in 16 ft. being permitted. 



* Prepared by the engineering department of the Chicago, Milwaukee & St. Paul Ry.; 

 fir. C. F. Loweth, Chief Engineer, and Mr. J. H. Prior, Office Engineer. 



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