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Reconstruction of the Railway Bridge over the Rhine at
Düsseldorf. PLatt.

(Centralblatt der Bauverwaltung, 1898, pp. 351 et seq.)

The bridge has a total length of 815.33 metres (2,674 feet), including four stream spans of 103.57 metres (340 feet), and carries a double track of railway. The river spans are crossed by girders, while the approaches are carried on brick arches 18.83 metres (61.8 feet) span. In 1895-96 it was decided to reconstruct the deck of the river bridge and to renew the covering and filling in of the arches, which had become leaky and sodden.

About seventy-three passenger and goods trains pass the bridge daily, and the plan adopted for reconstruction necessitated working the length over the bridge as a single line. The Author gives the regulations enforced for the safety of the traffic, and a diagram of the special signalling arrangements, &c.

On the arched part of the bridge the old filling in and asphalt was removed, and new asphalt laid down and covered with 5 centimetres (2 inches) of clean sand. Three small drain-pipes were laid longitudinally along the centre of the bridge embedded in the sand. A layer of bricks on the flat with open joints was placed on the sand, over this dry stone packing, and finally a depth of 40 centimetres (1.3 foot) of ballast.

While the bed of one pair of rails was relaid, that of the pair in use was supported by short timber struts from the side walls, which are very solidly constructed.

Prices in some detail are given, also five illustrations.

W. B.

The Kornhaus Bridge at Berne. P. SIMONS.

(Schweizerische Bauzeitung, 1898, p. 92. 12 Figs.)

Allusion was made to this bridge in the Minutes of Proceedings, vol. cxxxiv., and in the present Paper full details are given of the difficulties overcome. Considerable trouble was experienced with the foundations of the pier on the right bank of the river. Before the contract was let a series of bore-holes was made at about equal distances along the centre line of the proposed bridge. One of the bore-holes was in the centre of the site of the proposed pier on the right bank and a bed of clay was found at a depth of 37 feet. It was decided to make this the foundation and provide an air-pressure of 75 lbs. per square inch. As troubles with ground-water were expected, a sum of £800 was put aside to provide for pumping. In July, 1895, the work was begun, and instead of pumping it was decided to use sheet piling of steel of I section. This method was

employed quite satisfactorily on the left bank of the river, the points of the piles being driven 9.85 feet below the bottom of the foundation. As soon as work was begun and the slope of the Altenberg was cut into, it was found that the site was very different from what was anticipated. It was found that the bed of clay had a sharp dip across the axis of the bridge; water was also encountered, and it was found that an underground lake of considerable extent had been tapped; the water was eventually led off by two siphons. The quality of the ground was found to be so bad that the pier could not be built as originally intended, and other bore-holes, carried 85 feet below the proposed foundation-level, showed even worse results. Experts were called in, who decided that it was necessary to increase the area of the foundation 9.85 feet in each direction, and the site was to be surrounded with sheet piling and the whole area filled with pitch-pine piles, 40 feet to 50 feet long, which were to be driven by a steam pile-driver weighing 1,760 lbs. to 2,200 lbs. The Author gives details of the manner in which the work was carried out. The I-piling previously put in was removed with dynamite. The pitch-pine piles were from 12.6 inches to 15 inches square, and these were driven until a series of 10 blows with a ram weighing 2,200 lbs. drove the pile only 2 inches. Laying of the concrete foundation could only be begun on the 18th February, 1897; the concrete consisted of 440 lbs. of cement to 8 cubic feet of sand and 20·5 cubic feet of stone. This pier after completion only sank 0.39 inch.

E. R. D.

Arch Bridge over Schuylkill River, Fairmount Park,

Philadelphia.

(Engineering News, New York, 4 August, 1898, p. 67.)

There are four arch spans of 208 feet, and some smaller girderspans on each side, making a total length of 1,097 feet. Three arches, side by side, 28 feet apart support the platform, 79 feet wide, of which a concrete footway occupies 12 feet, a concrete carriageway 40 feet, and a double electric railway 27 feet. The arches are constructed on three hinges, with vertical posts and diagonals between arch and horizontal top member. Posts, diagonals and top members are made of two channel irons braced together, but as the channels are turned outward, the bracing stops at the assembling plates. Transverse bracing is placed between the arch members and the vertical posts. All connections are riveted. The bridge was designed and erected by the Phoenix Bridge Company. The article is fully illustrated.

M. A. E.

The Vierendeel Bridge.

Report by A. LAMBIN and P. CHRISTOPHE

(Bulletin of the International Railway Congress, October 1898, p. 1159.)

The bridge, 103 feet 6 inches span, designed for the Brussels Exhibition of 1896 by Professor Vierendeel of the Louvain University according to his new system, has girders with parallel flanges and verticals in the web but no diagonals, the corners of the rectangular panels being rounded and strengthened by an inner flange. It was tested to destruction in November, 1897, and this report was made at the instance of the Ministry of Public Works. It begins by setting forth the advantages claimed by the inventor, which are mainly as follows:

1

That the practical method of calculating stresses by assuming pivots in the booms in the centre of each panel is more accurate than that by assuming in a lattice girder pivots at the ends of each diagonal and vertical, and that the accurate method, based in both cases upon the assumption of the invariability of the angles formed by the members with each other at their junction, is simpler in the case of the new girder; that the deflection of the new girder is less; that it is more capable of withstanding blows and vibrations and less liable to rust; that therefore higher working stresses may be applied than in a lattice girder; that the new girder can be more easily and accurately put together, and that it is lighter and less costly.

The tests made with numerous apparatus for measuring deflections and variations of lengths are explained by calculations, tables of measurements and photographic views. The latter show that the weakest point was in the panel nearest to one of the supports; the web in the rounded corners lying in the direction of the missing diagonal tie was buckled laterally, and the web in the two other corners torn in more than one direction, as was expected; the right angles between the booms and the verticals. had been altered. Measurements of variations of lengths and observations of the effect of temperature lead the reporters to the conclusion that the alteration of the right angles showed signs of developing as soon as the operation of loading commenced (p. 1226), certainly previous to the limit of elasticity being reached according to the calculation. This would contradict the admissibility of the assumption on which the accurate calculation is based. Hence the degree of accuracy in the calculation of the new girder is of the same order as that of lattice bridges, and higher working stresses are not admissible. On these conditions the weight would

1 The great girder bridge over the River Wear at Sunderland belongs to this type; but as the girders are of the bowstring form the diagonal stresses in the web are comparatively insignificant, and not so much attention need be given to the construction of the rounded corners.-M. A. E.

not be less, but the difference is unimportant even if certain recommendations for strengthening the connections are followed. According to statements by manufacturers it appears that the cost would be slightly greater. In conclusion, so far as matters stand at present, the new girder is neither better nor worse than the lattice girder.

M. A. E.

Bridge Work on the Kansas City, Pittsburg and Gulf Railroad. (Engineering News, New York, 25 August, 1898, p. 114.)

The 50-foot and 60-foot spans are plate-girders. The truss of the 100-foot span is formed as a triangle, of 100 feet base and 40 feet height; it has four sub-divisions, so that the cross-girders are 25 feet apart. The connections are by pins. The 127-foot and 150-foot trusses of the riveted type, all struts being made of two channel-bars, the channels of posts and diagonals being turned inwards. The depth of the 150-foot truss is 28 feet, and the panel length 25 feet. The trusses are 17 feet apart. The 200-foot trusses are pin-connected. The 100-foot and 150-foot trusses are fully illustrated. The longest bridge on the line, the Arkansas River bridge, consists of a through span of 250 feet and eight deck spans 130 feet to 150 feet long, making a total length of 1,470 feet. The construction of the concrete piers is fully described by a reprint of the engineer's report.

M. A. E.

Bridge Disaster at Cornwall, Ontario.

(Engineering News, New York, 15 September, 1898, p. 274.)

Two of the three 368-feet span Pratt trusses, under construction for carrying the single line of the New York and Ottawa Railway over the St. Lawrence River, collapsed on the 6th September, 1898. The shore span, still supported on scaffolding, was fixed to the masonry pier, while the second span, without scaffolding, rested on rollers. The pier completely disappeared under the water. These circumstances led the writer to the conclusion that the girders were not at fault, but that the collapse was caused by undermining of the foundations by the current which runs from 5 to 8 miles per hour. The river is 35 feet deep; a timber crib, 18 feet by 62 feet and 35 feet high, had been sunk with some difficulty, and only after this had been done the ground could be examined by divers. Hard boulder clay being found, 50 cubic yards of concrete were deposited in bags and the remainder lowered in buckets of 1 cubic yard. When a level 4 feet under water was reached, work was stopped for the winter; then the crib was pumped dry and

masonry built to 35 feet above the water-level. This gives a height of 70 feet on the narrow base of 18 feet, and, moreover, as shown by a photograph, the pier was built out of centre to correct inaccuracy in sinking the crib. This, combined with the increased current through obstruction by the scaffold piles, seems to account for scouring under the pier as the cause of the disaster, causing the loss of fifteen lives and serious injury to sixteen men.

M. A. E.

Hygienic Regulations for Workers in Compressed Air.

L. BRENNECKE.

(Centralblatt der Bauverwaltung, 1898, p. 305.)

Following upon an earlier article, the Author gives in full thirtysix rules drawn up by Drs. Richard Heller, Wilhelm, Mayer, and Hermann v. Schrötter, for the regulation of workers in compressed air, and embodying the results of a long series of experiments conducted by them.

Among other points, it is stated that work can be carried on in pressures up to five atmospheres. The following Tables give the least times which should be taken in "locking" workmen in and out of compressed air :

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In all cases, the reduction of each 0.1 atmosphere pressure

should occupy at least 2 minutes.

1 Minutes of Proceedings Inst. C.E., vol. cxxxi. p. 398.

W. B.

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