Scientific American Supplement, No. 648, June 2, 1888. - Various

Rivets.—All rivets ⁷⁄₈ inch diameter, or ¹⁵⁄₂₆ inch when driven to fill holes; area of section, 0.6 square inch; bearing area, diameter × ³⁄₈ plate = 0.35 square inch, and for ¹⁄₂ inch plate 0.47 square inch. Post attachment,

considering all the twenty-six rivets doing duty, yields rivet strain as follows: In shear, single 5,000 lb. per square inch: and bearing area—¹⁄₂ inch plate—6,600 lb. per square inch.

Connection of ³⁄₈ Web to Flange Angles.—Taking the forty rivets between ends of girder and second stringer, the horizontal strain difference is 162,000 lb., the rivets being strained 3,400 lb. per square inch double shear, and 11,600 lb. per square inch bearing area. Taking distance from ends to first stringer, the horizontal strain difference is 105,000 lb., yielding on twenty rivets 4,200 lb. per square inch double shear, and 15,000 lb. per square inch bearing area. Taking a short distance of 2 feet from ends, the horizontal strain is 70,000 lb. on ten rivets, giving 5,800 lb. per square inch double shear, and 20,000 lb. per square inch bearing area. In these girders the weakness feared was in the end flange riveting and shear in end web, and caused the test recorded below. The test was recently made at the works of the Keystone Bridge Company, by means of hydraulic power applied at stringer points. Convenience made it necessary to make the test with the beam blocked up horizontal on the ground, so that the weight of the beam is necessarily neglected. The beam was connected with a pair of posts, precisely as in the actual structure, between which an additional girder was framed as a reaction base for the rams. The annexed diagram shows the general arrangements. The hydraulic power was derived from the testing machine plant of the Keystone establishment, and the deflections measured from a fine wire parallel to the lower flange, and about 3 inches therefrom. The diameter of the ram was 10 inches; area 78.54 inches. The record was as follows:

Gauge reading.	Load on each ram. lb.	Deflections. b in.	Total b' in.	load. lb.
565	44,375	¹⁄₈	¹⁄₈	177,500
1130	88,750	⁵⁄₁₆	⁵⁄₁₆	355,000
1412	110,900	³⁄₈	³⁄₈	443,600
	No permanent set in above
1695	133,125 uncertain.	—	—	532,500
	Permanent set scant ¹⁄₃₂ inch.
1980	155,500 not recorded.	—	—	622,000
	Permanent set ⁵⁄₃₂ inch.
2080	Failure commenced.	—	—	653,500

Failure commenced through giving way of angle irons, beginning in a fine seam in the first bend of the lower flange from the end support, the seam being along the root of the angle, which continual pressure tore apart across the angle as shown, when the web commenced to tear like a sheet of paper, in direction and manner as exhibited on plate herewith—from photograph. From some cause not apparent the deflections were not similar at the symmetrical end rams, a, the point where the web failed—left side—being sharply deflected. While the angles showed root fracture at the opposite point, the web did not fail or show indications of so doing, the deflection being on an easy curve. With the extreme yielding of the lower flange angles, the angle brackets connecting girder with posts commenced to go, tearing likewise along the root, and stripping the heads from the extreme upper rivets as shown. The internal diaphragm connecting the channel sides of the posts was unaffected. The rivets connecting the ruptured flange with web appeared as perfect as when driven, and no indication was disclosed, as far as it was possible to tell, of the holes in the web elongating or any upsetting of bearing surface. There is no telling what the web and rivets would have borne had not the solid angle irons given way at the first bend. It is to be noted that flange plate with leg of angle attached thereto was intact, showing no indication of rupture.

Discussion.—Taking that stage of the experiment when a permanent set was first noted—viz., ¹⁄₃₂ inch—the recorded load was 532,500 lb., or as near as may be 3¹⁄₃ times the basis on which the calculations in the first part of this paper were made—40,000 lb. on each stringer, or 160,000 lb. total. Applying this ratio to the preceding computations, the iron would be apparently strained as follows:

Flanges at:	m 3,800 × 3¹⁄₃ = 12,600 lb. per square inch (psi).
	a 5,700 × 3¹⁄₃ = 19,000 psi.
	b 6,400 × 3¹⁄₃ = 21,200 psi.

Web.	Between a and b, 2,600 × 3¹⁄₃ = 8,700 psi.
Web.	At least section, 8,000 × 3¹⁄₃ = 26,600 psi.

Rivets.	Post attachment:
	Bearing area, 6,600 × 3¹⁄₃ = 22,000 psi.
	Single shear, 5,000 × 3¹⁄₃ = 16,600 psi.
	Web and flange connections, end rivets:
	Bearing area, 20,000 × 3¹⁄₃ = 66,600 psi.
	Double shear, 5,800 × 3¹⁄₃ = 19,300 psi.