THE MEMPHIS BRIDGE.

22

dicate that in large bar's a comparatively high steel gives the best results,and, if they are well annealed, is quite as soft as it is desirable to have.On the other hand, in small bars as low a steel as is consistent with soundingots is probably the best material, but it must be remembered that intrying to get a very soft and ductile steel the chance of blow holes andother unsound features is increased. For one other reason the use of ahigher steel for heavy eye bars seems wise, as where heavy bars are usedit may generally (though not always) be assumed that the strain due- tolive load is small in proportion to that due to dead load.

In the west intermediate span, being the one which was built by A.& P. Roberts & Co., the riveted members were made of medium steelthroughout, the work being punched and reamed. In the other interme-diate span the requirements of the specifications were adhered to.

' a! contractors/ 1 ' 1

The contract for all the material for the superstructure was origi-nally taken by the Union Bridge Company, and about five eighths of thewhole was actually manufactured by them at their shop at Athens, Pa.,the remaining three eighths being made at various other places. Thelargest contract placed elsewhere was with A. <fc P. Roberts & Co., whobuilt one of the intermediate, spans and the deck span west of Pier IV,except the eye bars, the Union Bridge Company relinquishing this por-tion of their contract and a new contract being made with A. & P. Rob-erts & Co.

The other shops generally did their work as sub-contractors for theUnion Bridge Company, though in some cases special things were ordereddirect.

The actual weights and percentages manufactured by the different

shops were as follows:

Pounds. Per cent.

Union Bridge Company.. 10 432 020 63.0

A. & P. Roberts & Co. . 3 113 250 19.07

Elmira Bridge Works... 1 127 584 6.94

Lassig Bridge and Iron Works.. .. 806 617 4.94

Scaife Foundry and Machine Co. 423 963 2.59

Keystone Bridge Co.... 310585 1.90

Pittsburg Steel Casting Co. 61 935 0.37

New Jersey Steel and Iron Co.... 40 712 0.25

Pittsburgh Bridge Co. 7171 0.04

c '

16 323 837 100.00

The work manufactured by the Elmira Bridge Works consistedprincipally of web members of the central and intermediate spans.

The Lassig Bridge and Iron Works furnished the four vertical postsand portals at the ends of the central span besides some other webmembers.

The Scaife Foundry and Machine Company furnished the large cast-ings on the piers.

The Keystone Bridge Company furnished the anchor rods withinthe masonry of the anchorage pier, a quantity of eye bars, and the beatingplates upon the rollers on Pier II.

The Pittsburgh Steel Casting Company furnished the steel castingsover Piers II, III and IV.. .

The 15 in. expansion rollers, which -were very finely finished, weremade by the New Jersey Steel and Iron Company.

All the steel used in this bridge (except a small portion of that man-ufactured by A. A P. Roberts & Co.) was made by Carnegie, Phipps &Co., Limited (now the Carnegie Steel Company). It was all open-hearthsteel and a large portion of it was made in basic furnaces.

The work was manufactured in the several shops named, accordingto working plans prepared by the engineer of the bridge, and shippedto the bridge site ready for erection.

ERECTION.

A contract was executed on the 10th day of May, 1890, with WilliamBaird and Andrew Baird, comprising the firm of Baird Brothers, for theerection of the superstructure for a fixed sum, this sum being dividedbetween the several spans. The contractors received the material as itarrived, took responsible care of it and erected it in position. Therequirements which governed this erection are contained in the specifica-tions which form Appendix L.

All of the bridge except the suspended span between the cantileversof the channel span was erected on falsework. This suspended span wasprojected from the ends of the cantilevers, connected at the center andthen swung free.

Bents were placed under the panel points of the tresses. Each benthad nine posts, the centre post and the third post from each side beingplumb throughout, the other posts battered. All posts were of 12" X 12''timber/and the bents were. built in . three stories. The falsework wasbraced longitudinally by girths at each story, the girths at the ends beingbolted to the stone , piers. . . Each bent rested on 18 piles,* these piles

generally being cut off at elevation 205, or 11.2 ft. below high water. Onthe top:were placed 20 lines of stringers, four at the center and eight oneach side, to carry the traveler tracks. ;p,

This falsework terminated at the proper level to receive the bottomchord. Four Hues of rails, two on each side, were laid to carry thetraveler which was made long enough to reach over one and one half fullpanels, or three floor panels.

The material for the anchorage arm and the adjoining cantilever wasreceived on cars at the top of the bluff east of Pier I. All other super-structure material was received in a yard under the bluffs, where it wasstored and subsequently handled by barges. .m

Erection was begun on the east shore, and the traveler was set upon tlie ground back of Piet I; on the 31st of March, 1891, this travelerwas completed and ready to begin work, the falsework at that time onlyextending as far as Pier I. The first piece of bottom chord section wasplaced on the 3d of April, and the anchorage arm was virtually completedon the 6th of May. Meanwhile the falsework had been extended west-ward to the end of the east cantilever arm, and the erection of this canti-lever arm was practically completed on the 20th of June, though thefalsework and traveler were maintained in this position, and some furtherWork Was done on the last panel as late as July 31st.

The driving of the falsework for the central span was begun in July.The Work was begun west of Pier III, the piles for six bents being drivenwest of that pier. The two westward bents were placed close together,and on top of these were erected derricks by which the material waslifted from bars-es. The entire falsework between Piers II and III wascompleted by the end of August. This falsework was placed in themiddle of the Mississippi River immediately after the flood season. ItWas very heavy and expensive) the piles generally being from 90 to 100 ft.long and driven about 20 ft. in hard sand below the bottom of the river.

When this falsework was completed the traveler which had beenused on the east side was taken down and set up on the falsework. ItWas in itself a pretty large structure, standing 97 ft. above the track onwhich it ran and nearly 200 ft. above the surface of the water. Thistraveler when completed consisted of four bents, only three of which hadbeen used on the east side.

Two derricks were set up at the west end of the falsework west ofPier III, and all the members of the central span were taken by bargesfrom the material yard under the bluff on the east side of the river to thewest end of the falsework, where they were raised by the derricks to the