Plate Girder Bridge 1847

 

James Millholland was an early railway engineer for the Baltimore and Susquehanna railway. His biggest success was the development of anthracite (hard coal) burning steam locomotives but he helped bring railway technology from its infancy to the continent-spanning systems that dominated the end of the century. He was an innovative designer who applied himself all sorts of railway related projects, not restricting hiself to locomotives and rolling stock. Here is a plate girder bridge he designed in the mid 1840s.

 

 

The following letter, written by the designer to Mr. Herman Haupt of Engineering News, soon after the erection of the bridge, gives many details which will be of interest:

Dear Sir:

--Enclosed I send you the drawing of the thee bridges I constructed on the Baltimore & Susquehanna Railroad while engaged as Superintendent of machinery and road. The one marked A was built at the Bolton depot in the winter of 1846 and 1847, and was put in its place in April, 1847. This bridge is made of boiler-iron 1/4-in. in thickness. The sheets, standing vertical, are 38 ins. wide and 6 ft. high, and riveted together with 5/8 rivets, 2 1/2 ins. from centre centre. You will observe reference to the drawing, that each truss frame is composed of two thicknesses of iron, 12 ins. distant from each other, and connected by 5/16 iron bolts, passing through round cast-iron sockets at intervals of 12 ins.; which arranged, together with the lateral bracing between the two trusses, ensured stability. The lateral bracing is composed of 3/4 round iron, set diagonally and bound together at the crossing by two cast iron plates about 4 ins. diameter, the sides next to the bracing being cut in such a manner, that when the two 5/8 bolts that pass through them were screwed up, it held them firmly together. There is also a bolt passing through both truss-frames and through the lateral bracing, at right angles with the bridge, which secures the heels of the lateral braces, and by means of a socket in the center made a lateral tie to the bridge giving the bridge its lateral stability.

The lower chords were of hammered iron, there being some difficulty at the time to get rolled iron of the proper size, and are in one entire piece, being welded together from bars 12 ft long. There are eight of them, 5 x 3/4-in, one on ether side of each piece of boiler iron, and fastened to it with 3/4-in. iron rivets 6 ins. distant from each other. there are but four top chords and of the same size of the bottom, two on each truss near the top, the timber for the rail making up the deficiency for compression, and answering the purpose of chords. This bridge was built at the time Messrs. Stephenson and Brunel were making their experiments with cylindrical tubes preparatory to constructing the Menai bridge; the cylindrical tubes failing, they adopted this plan of bridge.

 The entire weight of the bridge is 14 gross tons, and cost $2,200; but as the same kind of iron of which the bridge is composed of can be had for at least 15 per cent less now than it cost at the time, it would be but fair to estimate the cost of the bridge at $1,870, without any reference to the labor that misapplied in all new structures of any kind, making the cost of a bridge 55ft. long $35 per ft. And I have no doubt where there would be large quantity of iron required for such purposes, that it could be had at such prices as to bring down the cost of bridges of 55 ft. length to $30 per ft.

very respectfully yours,

James Millholland

John H White; James Millholland and Early Railroad Engineering.

Smithsonian Press 1967