30 1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[October, 



ttention to regularity all the more striking is, that in order to make a 

 front of pach ol these sides, ii great number of blank or we suppose sham 

 windows glnzed liko the others, are introduced, viz., six out of the 

 eight in both the mezzanine and principal floor, thus making a total of 

 twenty-four shim windows I! Notwithstanding this license and that 

 taken in regard to spacing the windows, some of tliem come in very 

 awkwardly in the interior, and in such a manner as utterly to destroy all 

 symmetry : the hall, for instance, is chiefly lighted by one of the win- 

 dows in the adjoining corridor, which is open to it; but instead of 

 those windows being exactly on the line of the axis of that hall they 

 arethrownoutof it, so as to fall in the line of one of the two pillars form- 

 ing the screen between the corridors and the ends of the hall. Much con- 

 sideration does not appear to have been given to bearings, for there 

 are solid walls carried from back to front across the ceilings of some 

 of the ground floor rooms, of just the same thickness as the external 

 ■walls ! at least so they are shown in the plan. And yet, notwithstand- 

 ing all the incongruities we have pointed out— nor are they the only 

 ones that we detect — we are told that Mr. Tite not only heartily ap- 

 proved of the design — qiicsre the design or intention of a building 

 being erected— but actually executed the drawings, at least had them 

 executed in his own office. Executed, no doubt, they were with 

 the utmost scrupulousness and literal fidelity as to following co/;!/ ; 

 otherwise a few very much needed corrections would probably have 

 been made in them. However, the design has answered our purpose 

 better just as it is ; and we dare say we have bestowed very far more 

 notice upon it than it would have obtained from any one else, and so 

 far it has been singularly lucky in having fallen under our inspection 

 instead of that of one of those short-winded critics who wiiuld have 

 dismissed it without saying more than that it was in the Italian style. 



FALL OF THE BALLEE KHAL SUSPENSION BRIDGE, 

 NEAR CALCUTTA. 

 At a lime when public attention is directed to the subject of Sus- 

 pension Bridges any information respecting the failure of so important 

 a structure as the bridge over the Bailee Khal cannot fail to be in- 

 teresting. We are indebted to several correspondents for communi- 

 cations respecting the nature of the accident, from which we have 

 obtained our information. In the JMtchanics J\Iagazine, in Oct. 1844, 

 appeared the following account of the structure, accompanied by en- 

 gravings, the vi'ood cuts of which have been courteously sent us for the 

 illustration of the present article. 



"Description of a Suspension Bridge on Mr. Dredge's principle, erected 



over tlie Bailee Klidl, for the Indian Government, from the designs, 



a7id under the superintendance of Cap/tain Goodmyn, R.B.E. 



Fig. 1 of the accompanying engravings is an elevation of one-half 

 of this bridge, and fig. 2, a plan of one-half of the superstructure. 



Fig. 3 is an elevation in section of the principle parts of the other 

 half of the bridge, showing the manner in which the chains are 

 secured. 



Fig. 4 is a plan of the foundations of the parts represented in 

 fig. 3, 



Fig, 5 is a tranverse elevation of the one of the piers on a larger 

 scale than in fig. 1. 



The Bailee Khal is about four miles north-west of Calcutta. The 

 bridge consists of a single curve of 250 feet span, with 18 feet width 

 of the platform. The height of the points of suspension above the 

 plauk level, which is equal to the deflection of the chains, is 2G feet, 

 "f 9-6T the chord line nearly. The angle of suspension, is therefore 

 about 19° 51'. The platform is supported by two main chains, 

 one on each side of the bridge, composed of links of round bar iron 

 1| in. in diameter, and 10 feet long ; there are 15 of these links rest- 

 ing on the towers at each point of suspension, and from thence at 

 each joint the number is lessened one link, till at the centre the sec- 

 tional area of the chain is reduced to two bars ith inch in diameter. 

 The oblique suspending rods depend from the chains at each joint in 

 pairs; they are ith of an inch in diameter, and the angles at which 

 they are attached to the platform vary from G7'42', to 10°, becoming 

 more and more acute as they approach nearer the centre of the bridge. 

 There are three pairs of these suspending rods at each point of sus- 

 dension, which support 23 feet of the roadway at each end of the 

 bridge, taking the weight thereof immediately to the tower link, with- 

 out etTecting the curve of the chains. Thus, 250-23x2=204 feet= 

 the length of platform supported by the chains. 



Now the tension at the points of suspension is equal to half weight 

 (of bridge and traffic jointly taken at 12blb. per square foot) x cose- 



cant of angle of suspension, or —r- 2'91=:289-6 tension, for which 45 



square inches is allowed, and as the strain to which each bar was sub- 

 jected before erection was 10 tons per square inch, there is a strength 

 of iron sufficient to resist 450 tons. 



The angle of the first auxiliary from the chain is double that of 

 the first chain link, and the common ditference of the whole series, \» 

 double that of the diflference between any two cons ecutive links of 

 the chain. The pull on the rods is thus as nearly as possible in tb» 

 direction of their length, and the horizontal force is resisted through 

 the horizontal line of the platform. The angle formed by the last 

 link of the chain, and the horizontal, or central one, is 5°, and that 

 of the centre auxiliary 10°, so that the last link bisects the angle 

 formed by the centre link, the centre auxiliary, and as these forces 

 are nearly equal, the last link is in the best possible position for pre- 

 serving the equilibrium at the junction, and not allowing the centre 

 link to be strained beyond its power. 



The back chain forms a continued line from the rear bolt of the 

 tower links at an angle of 25°, the section of iron being the same 

 throughout as that of the tower links. The mass of masonry to which 

 the chains are secured contains 7,000 cubic feet, which, with the com- 

 pletion of the parallelogram from the point where the back chains meet 

 the road level, gives nearly 19,000 feet of resisting matter on each 

 side, or about double what is due to the most severe tension. 



Between the 2nd and 3rd links of the back chains are a series of 

 adjusting loops and eyes, similar to those of the Menai Bridge, ad- 

 mitting of 4 inches correction. 



Two back stays depend from the end of the rear tower bolts, and 

 are together in power equal to the three pairs of auxiliaries, to com- 

 plete the connexion between which and the back stays, bars are intro- 

 duced or added to the tower links, coupling in with the oblique rods 

 front and rear, and equalizing the bearing on the tower link bolts. 



These stays are keyed beliind cast plates abutting against stone at 

 the base of the wing walls, and tend to assist in the support of the 

 towers, as well as to counteract the effect of any violent pull on the 

 tower links by a sudden weight impinging on the platform. 



The level of the platform is IS feet above the ordinary, and 10 feet 

 above extreme flood rise, and is composed of two external longitudinal 

 beams 5 in. by J in., to which are attached, by means of cast boxes, 

 the transverse beams of T-iron, (4 in. by | in. web.) and (3 in. by | in. 



