THE 



CIVIL ENGINEER AND ARCHITECT'S 



JOURNAL. 



WROUGHT-IRON TUBULAR BOW BRIDGE. 



CWith an Engraving, Plate I.J 



In consequence of the tubular form becoming a favourite mode 

 of constructing bridges of wrougbt-iron for railivay purposes, we 

 are induced to give an engraving of a wrougbt-iroii tubular bow 

 suspension bridge for crossing the Ouse river in Norfolk, designed 

 by Mr. W. C. Harrison, who has had considerable experience in 

 the construction of some large timber bow suspension bridges on 

 some of tlie Norfolk railways. 



Mr. Harrison observes, — " The facility with which a how bridge 

 of this construction, with boiler-plate, could be put together, ap- 

 peared so eWdent, that he felt convinced of its practicability and 

 usefulness for railway purposes, in crossing rivers and valleys, to 

 almost any extent. A bridge of this kind could be easily put 

 together, by the same kind of workmanship as in steam boilers, in 

 a manufactory in any part of the country, and in certain conve- 

 nient lengths of 10, 15, or 20 feet each, for the purpose of trans- 

 porting to its destination, so that there will be but a few joints to 

 ri^'et up when put in its place. The bow being hollow, and also 

 the tie-beam, or string as it may be termed, gives the opportunity 

 for a man to get inside to hold up the rivets for the workmen out- 

 side to rivet the parts together. 



" The bow and string are to be made of plate-iron, of such a 

 thickness as is most suitable to the size of the bridge intended to 

 be constructed, and joined at the angles with angle-iron; audit 

 will be perceived from the engraving how perfectly well connected 

 the extreme ends of the tie-beam and bow will be by the manner 

 shown, which is a plate extending over the tie and bow, firmly 

 rivetted to each, thereby answering the purpose of an abutment to 

 the bow, and gi\ing perfect security in a \ital part. 



" The elevation of the bridge shows both the suspending and 

 cross-brace bars, being all of jilate-iron, from the facility of getting 

 bars in this shape so easily made, and requiring so little workman- 

 ship — namely, the rivet holes made in their ends. 



"The design is for a span of 170 feet and two lines of rails; 

 consequently, there are three bows. Fig. 1 is the elevation of one- 

 half the span, with the suspending bars a a and li h ; drt, the abut- 

 ment plates, as they may be called; c, the cross-beams, which may 

 be of iron or timber. Fig. 2, a view on the top of the bows, with 

 some of the cross-beams, c, extending outside (as also seen at fig. 3, 

 the end elevation), to receive the lower ends of the struts going up 

 to the top of the outside of the bows, to give steadiness to the 

 whole ; but these can be used or not. Fig. 3 shows the distance- 

 pieces and cross-frames betwoen the bows. Fig. 4 is a section of 

 the cross-beams or girders, which may also be made of wrought- 

 iron plate and angle-iron, or wood, to carry the timber sleepers of 

 the rail. Fig. 5 is an enlarged section of the bow and string, and 

 the distance-piece between the suspending bars." 



Mr. Harrison proposes for a bridge of the span shown in the 

 engraving, that the bow should be constructed of half-inch plate- 

 No. 12-1— Vol. XI.— January, 1SJ8. 



iron, i feet deep by 3 feet wide ; and the tie-beam or stringer 

 2 ft. 6 in. deep by 3 feet wide. 



Next month we will endeavour to offer some remarks on the 

 construction of bridges of the tubular form, as to their applica- 

 bility for railway purposes. 



A DEFLECTION OR VIBRATION GAUGE. 

 By George Howard Fexwick, C.E. 



The accompanying engraving, fig. 1 

 (drawn to one-tiiird the full size), is a 

 gauge for registering the vibration or 

 deflection of railway girders. A is a 

 piece of wood or metal, made to slide in 

 another piece, B, which is held in posi- 

 tion by a slight pressure of two springs. 

 G and F, as shown on plan fig. 2 (drawn 

 full size). On the face A are two ar- 

 rows at C, whicli can be moved to any 

 of the holes at D for adjustment. It is 

 supposed to be set at zero, and as it re- 

 ceives the pressure from tlie girder E it 

 is pressed down, thereby registering the 

 deflection of the girder on a decimal or 

 mechanical di\ided scale on B. This 

 gauge may be applied by being sup- 

 ported by a frame let into the sides of 

 the walls which the girders span, and so 

 made to travel to any particular place, 

 such as the centre or springings; or 

 may be placed upon a staff' for conveni- 

 ence, similar to a levelling staff. 



G. H. F. 



[This simple and ingenious contriv- 

 ance might, perhaps, be improved by 

 fixing a vernier on the slide D, divided 

 so as to indicate the hundredth parts of 

 an inch; the side scales being divided 

 into inches and tenths.] — Editor. 



^L- 



Fig. I EUvation, 



Fig. 2, Plan. 



