The Forth Bridge/Weight of the Superstructure

by Wilhelm Westhofen

Weight of the Superstructure.

The subjoined tabular statement will give some idea of the amount of steel distributed over the main supports.

Description of Parts.						Fife.		Inchgarvie.		Queensferry.		Total.
						Tons	Cwt.	Tons	Cwt.	Tons	Cwt.	Tons	Cwt.
3 Central towers, including bedplates					…	4815	16	7036		4815	16	16,667	12
6 Cantilevers		…	…	…	…	1 fixed 1 free		2 free		1 fixed 1 free
Bay 1	…	…	…	…	…	4235	4	4312	12	4235	4	12,783
" 2	…	…	…	…	…	2626	2	2658	12	2626	2	7910	16
" 3	…	…	…	…	…	1764	6	1724	16	1764	6	5253	8
" 4	…	…	…	…	…	1034	3	1009	16	1034	3	3078	2
" 5	…	…	…	…	…	665	18	620	4	665	18	1952
" 6	…	…	…	…	…	490	2	423	12	490	2	1403	16
2 Central girders		…	…	…	…	410	15	821	10	410	15	1643
Rocking-posts and steel castings				…	…	51	9	51	9	51	9	154	7
Ladders in tubular members				…	…	36		40		36		112
Totals				…	…	16,129	15	18,698	11	16,129	15	50,958	1

Weight of a	fixed cantilever: 5441 tons.
""	free cantilever: 5375 tons.
""	1710 ft. span: 11,571 tons 10 cwt.
""	cantilever bridge per foot run: 9 tons 11 cwt.

Table No. XII. on the next page shows the quantities of steel erected and bolted up and rivetted during the years 1887, 1888, and 1889, month by month. These quantities apply to the three main piers of the cantilever bridge only.

The total cost of the foundations of the Forth Bridge may be roughly put down as nearing 800,000l; and in connection with this expenditure it is necessary to mention the name of Mr. P. W. Meik, who acted as resident engineer for, and as representative of, Messrs. Sir John Fowler and Baker from the commencement in 1883 until the completion of the masonry piers in 1886, and of whose unfailing tact and courtesy his many friends retain the liveliest remembrance.

Another name should be added here, that of Mr. William Gray, who from start to finish had charge of all excavation and masonry work, besides other duties of the most multifarious character, and of whom it may be truly said that, day or night, early or late, no one would ever call upon him and find him unwilling to do what was wanted.

The total expenditure by the Forth Bridge Company upon construction has been as follows. The figures are approximate amounts as far as expenditure year by year is concerned, but the total amounts are correct and authentic.

	For half-year ending
These amounts include the expenditure for the construction of the north and south approach railways, but nothing for the connecting line.		₤
	December 31, 1882	7000
	June 30, 1883	42,800
	December 31, 1883	57,000
	June 30, 1884	119,000
	December 31, 1884	218,200
	June 30, 1885	231,000
	December 31, 1885	216,000
	June 30, 1886	188,000
	December 31, 1886	253,500
	June 30, 1887	240,000
	December 31, 1887	243,000
	June 30, 1888	195,700
	December 31, 1888	218,000
	June 30, 1889	182,000
	December 31, 1889	138,000
	Total……	2,519,200
Add to this the amount expended in connection with Sir Thomas Bouch's suspension bridge (including all parliamentary expenses)		250,000
		2,799,200
Parliamentary expenses in connection with cantilever bridge, engineering expenses, interest during construction, &c.		378,006
Total expenditure to January 1, 1890		3,177,206

It is estimated that a further sum of 50,000l. will be required to complete the structure, the painting included.

The sale of plant is expected to realise fully 120,000l.

For the erection alone of the Fife, Inchgarvie, and Queensferry Piers, that is, everything on top of the circular granite piers which may be strictly called the superstructure, the amount of wages paid including salaries of officials in charge of the piers, amounted up to November 30, 1889, to a total sum of 344,810l; the total amount of steel put up and rivetted up to that date being 50,064 tons. The cost of labour for that work is therefore 62. 17s. 9d. per ton erected and rivetted up.

The total amount of wages and salaries paid on the works up to January 1, 1890, was 1,045,000l.