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APPENDIX N.

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SUPPLEMENTARY SPECIFICATIONS, JANUARY 1. 1891.

MODIFICATIONS OF SPECIFICATIONS FOR SUPERSTRUC-TURE OF BRIDGE ACROSS THE MISSISSIPPI RIVER

AT MEMPHIS, TENN„ ACCEPTED DECEMBER 29TH,

1890.

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STEEL.

10. Steel will be divided into four classes : first, High Grade Steel, whichshall be used in all the principal truss members except eye. bars ; second, Eye-bar Steel, which shall be used ouly in eye bars; third, Medium Steel, whichshall be used in the floor system, laterals, portals, traverse bracing and thelacing of the truss members ; fourth, Soft Steel, which shall be used only forrivets, and at the option of the contractor where wrought iron is permitted.

11. The bolsters which carry the large pin bearings on Piers I, II and IIIshall be of cast steel.

12. In any case where it seems doubtful what quality of steel is required,High Grade Steel shall be used.

13. Steel shall be made by the open-hearth process, but no steel shall bemade at works which have not been in successful operation for at least oneyear.

14. All steel shall be made from uniform stock low in phosphorus, and the

manufacturer shall furnish reports of the analysis of every melt, certified by achemist satisfactory to the Chief Engineer. f

15. In the finished product of acid open-hearth steel the amount of phos-phorus shall not average more than yf-j- of one per cent, and never exceed j 1 ^ ofone per cent.

16. In the finished product of basic open-hearth steel the amount of phos-phorus shall not average more than of one per cent, and never exceedygy of one per cent.

17. A sample bar three-quarters of an inch in diameter shall be rolledfrom a four-inch ingot cast from every melt. A laboratory test shall be madeon this sample bar in its natural state without annealing, but this test may bemade subsequent to the acceptance of the material and shall be for recordonly.

18. A second sample bar having a cross section of one square inch shallbe cut from the finished product of every melt. The second laboratory testshall be made on this sample bar in its natural state without annealing.

.P 19. In the laboratory tests all observations is to elastic limit, ultimatestrength, elongation and reduction shall be made on a length of eight inches.

20. A piece of each sample bar shall be bent 180 degrees and closed up

against itself without showing any crack or .flaw on the outside of the bentportion. Two successful tests out of a total of three will be accepted as satis-factory. l0

21. The first laboratory test shall meet the following requirements:

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' — High Grade Eye-Bar

■ and Medium Steel. Soft Steel.

Minimum Ultimate Strength, pounds per square inch.. -.65 000

Minimum Elastic Limit, pounds per square inch.. 38 000

Minimum Percentage of Elongation in 8 inches... ... 20

Minimum Percentage of lteduclion at Fracture. v .... 40

57 00032 0002850

Hȣh Grade

Eye-bar

Medium

Soft

Steel.

Steel.

Steel.

Steel. !

i. 78 500

75 000

72 500

,63 000

. 69 000

66 000

64 000

55 000

. 40 000

38 000

37 000

30 000

18

20

22

28

38

40

44

50

Of ..

0. !■¥

22. The second laboratory, test shall meet the following requirements:

Maximum Ultimate Strength, pounds per square inch. 78 500Minimum Ultimate Strength, pounds per square iuch. 69 000

Minimum Elastic Limit, pounds per square inch. 40 000

Minimum Percentage of Elougation in 8 inches.

Minimum Percentage of Reduction at Fracture.

23. If the ultimate strength comes within five hundred pounds of the

maxinmm or minimum limit, a second test will be made, and both tests will berequired to come within the limits. ^

24. Every melt which does not conform with these requirements shall berejected. Cases in which the tests are thought not to give fair representationsof the character of the material shall be referred to the Clnef Engineer.

25. A full report of the laboratory tests shall be furnished, certified by aninspector accepted by the Chief Engineer.

26. The broken and bent specimens shall be preserved subject to tlieorders of the Chief Engineer.

27. Notices shall be sent in duplicate to the Chief Engineer at his Chicagooffice and to the Shop Inspector at the works.

28. Analyses shall be made by the manufacturer of every melt, showingamount of phosphorus, carbon, silicon and manganese, and certified copies ofthese analyses shall be furnished to the Mill Inspector, who will forward themto the Chief Engineer. The phosphorus and carbon analyses shall always bemade. Analyses for silicon and manganese shall be made whenever called for

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by the Inspector. Copies of all analyses, whether made by request of theInspector or by the desire of the manufacturer, shall be furnished to the ChiefEngineer.

29. Duplicate reports in full detail, including reports of chemical analyses,shall be sent to the Chief Engineer at his Chicago office, and also to the shopInspector at the works, not later than the day on which the accepted materialis shipped.

30. Two notices of shipment of manufactured material, identifying themelts and dimensions, shall be mailed on the day after such shipments aremade, one to be sent to the Chief Engineer at his Chicago office, and one tothe Shop Inspector at the works.

31. Every finished plate, bar or angle shall be stamped on one side nearthe middle with a number identifying the melt, and this stamp shall besurrounded by a heavy circle of white paint. Steel for pins shall have the

i melt numbers stamped ou the euds. Bivet and lacing steel and small pieces:s ' for pin plates and stiffeners may be shipped in bundles securely wired togetherwith the melt number on a metal tag attached.

32. The finished product shall be perfect in all parts and free from irregu-larities and surface imperfections of all kinds.

33. The cross sections shall never differ more than two per cent from theordered cross sections as shown by the dimensions on the plans.

34. All sheared edges shall be planed off so that no rough or shearedsurface shall ever be left on the metal.

35. Steel for pins more than four inches in diameter shall be hammered

steel, and tests shall he made on this steel in accordance with the requirementsof Section 22. ^ In such tests au elongation of fifteen per cent, and a reductionof area of thirty per cent., given in each of two test bars tested separately, willbe accepted as satisfactory, provided the character of the fracture is satis-factory. The bending test required in Section 20 shall be made on pin steel,but pin steel will, not be rejected, provided the bar will bend around a circle ofa diameter equal to twice the thickness of the bar without cracking. Steel forpins shall be sound and entirely free from piping. All pins in the maintrusses shall be annealed before they are turned and shall be drilled throughthe axes. . **

GEO. S. MOBISON,

Chief Engineer.

January 1, 1891.

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