1845.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



I6S 



HUNGEREORD SUSPENSION BRIDGE. 

 ( U'tlh Three Engravings, Plalea XIII, XIF, and XV.) 

 We present our readers in the accompanying engravings with ample 

 illu^tralions of the details of the Suspension Bridge recently erected 

 oyer the Thame«, and cpnni'cting Hiingerford Market with Lambeth 

 on the opposite bank of the rivir. The engravings are carefully re- 

 ducfd geiimetrically from the original working drawings, and by the 

 scale attached represent accurately (he dimensions of the parts illus- 

 trated. The details are highly interesting and exhibit a more than 

 ordinarv scientific judgment in'obviating ditTiculties which are usually 

 attendant upon suspension bridges,— to these details we have con- 

 fined our illustrations, as a drawing of a bridge of such large magni- 

 tude as the one before us must necessarily have been on such a very 

 small scale, that it would have been perfectly useless to our profes- 

 sional readers. 



The Hungerford Bridge is now the ninth structure connecting 

 the two parts of the metropolis on either bank of the Thames — the 

 Vauxhall Bridge being the extreme western, and the Thames Tunnel 

 extreme eastern ol this noble range of public works, unparallelled for 

 their magnificence throughout the world. The following account is ex- 

 tracted from a paper read by Mr. Cowper bclore the Royal Institu- 

 tion. 



"This bridge is for foot passengers only: it consists of four broad 

 chains, viz. two chains, one above the other, en each side of the plat- 

 form ; each chain consists of ten and eleven links alternately, and near 

 the piers of eleven and twelve. This increased strength is to meet 

 the increased strain which takes plaee near the piers. The chain of 

 the Menai bridge is only five links wide, and the chain of the Hammer- 

 smith only six links w ide ; but the great breadth of the Hungerford 

 chain (viz. eleven links, or about two feet,) gives them great power to 

 resist the effects of the wind, and thus prevent vibration. Two 

 brick towers, or campaniles, in the Italian style, are built in the river, 

 over which the chains are carried, forming thus a central and two side 

 spans. 



The two piers are in height 80 feet. 



The central span between the piers (being 110 feet wider 



than the Menai Bridge) 6764 feet. 



The length between the abutments 1352^ feet. 



Deflection of the chain 50 feet. 



Length of each link (7 in. wide, 1 in. thick) 24 feet. 



Weight of each link 5^ cwt. 



(The connecting pins are 4| inches diameter.) 



The whole number of links 2600 



Their weight 715 



The number of links in the centre spaa 1280 



Their weight 352 



Width of the platform 14 



Height above high water nt the centre of centre span . . 32 J feet. 



near the piers 28| feet. 



(Giving a rise of four feet in the centre. This gives 

 additional height for the river traffic, and produces a 

 graceful curve, and prevents any appearance of swag- 

 E'lg) 

 The section of the chains at the centre of centre span is 296 sq. in. 



near the piers 312 sq in. 



A square inch of iron breaks with 27 or 29 tons, but 174 tons is 

 taken as the impairing weight, j. e. the weight at which it begins to 

 stretch ; we have, therefore, for the weight the bridge will actually 

 bear, — 



296 X 17i tons = 5180 tons, while 296 x 5 tons = 1480 tons, 

 is the greatest load that can be put upon it. This is taking a crowd 

 standing close together to be 100 lb. per square foot. The entire 

 weight of the chain, the platform, and a full load upon it, would make 

 a load of about 1,000 tons on each pier, being about 8J tons on each 

 square foot of brick-work, or not quite li cwt. on each square inch. 



The chains are attached to large wrought-iron vertical plates at the 

 summits of the piers : these plates are firmly bolted together, and also 

 to a strong horizontal plate, — the whole forming what is called a sad- 

 dle. The saddle is not fixed to the pier, but rests on fifty friction 

 rollers, these resting on a thick iron plate, which is supported by a 

 solid mass of iron and timber girders. The pier itself, being piercf d 

 with arches, may be considered to consist of four columns of brick- 

 work ; the girders, therefore, are so arranged, that no weight is thrown 

 on the archts, the whole weight resting on the columns. The saddle 

 is capable of moving eighteen inches each way, equal to three feel 

 entire motion ; so that if either span were crowded the chains would 

 adjust themselves, and the strain be still perpendicular upon the piers, 

 and have no tendency to pull the pier over. The method of putting 

 up the chains was thus: — Two sets of wire ropeft) each consistiog of 

 tto. S3.— Vol. YIII.— Jl;^B, 1815. 



tons. 



tons, 

 feet. 



three ropes, were hin)g from abutment to abutment over the piers, in 

 the exact situation the chains were to occupy,— these scaffold ropes, 

 as thev may be called, being distant from each other equal to the 

 length' of the connecting pin. A few feet above the scifTold ropes, 

 two other ropes were hung in like manner; on these traversed two 

 light boxes, very much resembling a carpenter's bench turned topsy- 

 turvy. These cradles, as they are called, were connected together, 

 and contained two windlasses, like those over a common well; these 

 cradles held the workmen. A barge containing the links was moored 

 under the cradles: four men in the cradles hauhd up a link ; and 

 when they had raised it above the scafTuld ropes, the connecting pin 

 was put through, and the pin being allowed to rest on the scaiTold 

 ropes, of course supported the link. The cradles were then moved 

 forward, and two liidis joined to the single link, then one joined to the 

 two; the chain consisting, thus, in the first instance, of alternately 

 two and one links. When this iwo-and-one-llnk chain was completed, 

 the scafibld ropes were not required, the two-and-one-link chaio 

 forming, as it were, a scaffold for the rest of the links ; and thus was 

 this bridge erected mithout any scnffolding but these few ropes, and 

 without the slightest impediment to the navigation, and without a 

 single accident. The cost was — 



Mr Chadwick's contract for brickwork, stone work, and coffer daiDS £63,000 

 Sandys, Carne and Vivian for iron work 17,000 



£80,000 



The money was raised by — 



3200 Shares of 25/. 

 By Loan 



£80,000 

 26,000 



The engineer in chief was Mr. Brunei. The resident engineer Mr. 

 P. Piitchard Baly." 



The first large suspension bridge erected in this country was that 

 constructed at Berwick, across the River Tweed : the length was 450 

 feet, and the engineer of the bridge was Capt. Sir Samuel Brown. 

 The method of constructing bridges by suspension is one of the oldest 

 in the annals of engineering. Examples of an exceedingly remote 

 date are found in China, and among the aboriginal works of North 

 America, but it was not until 181G that Sir Samuel Brown took out a 

 patent for the construction of chain suspension bridges in this country. 



The comparative span, weight, and cost, of the three largest suspen- 

 sion bridges in Europe are : — 



Freiburg (wire-rope). . 820 feet span. . 902,572 lb. weight. . £107,000 cost. 

 Hungerford (chain) ..676 „ ..1,601,600 „ .. £80,000 „ 

 Menai (chain) ..580 „ ..3,987,664 „ ..£120,000 „ 



It will be seen that the weight of the wire bridge of Freiburg is 

 only one-fourth that of the Menai bridge, though 294 feet longer; the 

 difference of cost is also £13,000 in favour of the former structure. 

 It may, however, be doubted whether a wire bridge is as secure as 

 one formed of fiat iron bars bolted together, as in the former case the 

 metal is liable to much greater injury by oxidation. The Menai 

 bridge was constructed in 1S2G by Mr. Telford, and at a time when 

 engineering effort? were comparatively unaspiring, this work was con- 

 sid°ered a wonderful monument of Mr. Telfoid's talents ; but it is now 

 perhaps, notwithstanding the difficulties overcome in its construction, 

 considered by engineers rather as a proof of courageous, than of per- 

 fectly succes'sful, enterprise : it has been subject to a great many 

 serious accidents, which would probably have been avoided had it been 

 erected at a more mature period of art. 



The arrangement of the bars forming the compound chain on either 

 side of the roadway of the Hungeiford Bridge may be repesented 

 thus — 



ViViViVi'i'i' 'I'.'i'iViVAV 



—It will be seen that by this arrangement each chain consists alter- 

 nately of 10 and 11 parallel flat bars. The head of each of these bars 

 is perforated to receive a long straight bolt which connects each two 

 series of liars together. 



In the Hammersmith bridge the arrangement is thus— 



Ml I I 1 I I I MINI I I I 



Ml II II I I II M II I II 



—Here the bars are arranged bv threes and sixes : the consequence 

 of the bars iu each series beiiij; of an even immber is that their heads 

 cannot overlap and be connected by a single bolt, as in the Hungerford 

 bridge ; but the connection is necessarily formed by a double coup- 

 ling bolt. In the Hammersmith bridge the wide uiterval between 

 the chain is the roadway, and the two narrow intervals are footways. 



22 



