# How to use *Girder* in a sentence

The underside of the stiffening

**girder**is 82 ft.It is the junction between the Oudh & Rohilkhand and East Indian railways, the Ganges being crossed by a steel

**girder**bridge of seven spans, each 350 ft.On the first English railways cast iron

**girder**bridges for spans of to 66 ft.Each

**girder**is 1511 ft.A main

**girder**consists of an upper and lower flange, boom or chord and a vertical web.AdvertisementIn the case of braced

**girder**bridges, the wind pressure is taken as acting on a continuous surface extending from the rails to the top of the carriages, plus the vertical projected area of so much of one**girder**as is exposed above the train or below the rails.Then w 3 = (w l +w 2)1 2 /(Cds-1 2) = (w i -Fw 2)lr/ (Cs -lr), where C is a constant for any type of

**girder**.Masonry bridges are preferable in appearance to any others, and metal arch bridges are less objectionable than most forms of

**girder**.As railway loads increased and greater spans were demanded, the Howe truss was stiffened by timber arches on each side of each

**girder**.Generally a

**girder**supports both a dead with a travelling load like a railway train, this is greater for partial and a live load.AdvertisementThe bracing bars, therefore, for this part of the

**girder**must be adapted to resist either tension or thrust.Next let the loads advance a distance a so that W2 comes to C. Then the shear at C is R(n+a)/l - WI, plus any reaction d at B, due to any additional load which has come on the

**girder**during the movement.Let W 1, W2, W3 traverse the

**girder**from the left at fixed distances a, b.As the loads move over the

**girder**, the points C, D, E describe the parabolas M1, M2, M3 i the middle ordinates of which are 4W 1 1, 4W 2 1, and 4W3l.Till W 1 has advanced a distance a only one load is on the

**girder**, and the curve A"F gives bending moments due to W 1 only; as W1 advances to a distance a+b, two loads are on the**girder**, and the curve FG gives moments due to W 1 and W2.AdvertisementWith short bridges it is best to draw the curve of maximum bending moments for some assumed typical set of loads in the way just described, and to design the

**girder**accordingly.If the load rests directly on the main

**girder**, the greatest -Iand - shears at C will be wXAGC and -w X CHB.A frame used to support a weight is often called a truss; the stresses on the various members of a truss can be computed for any given load with greater accuracy than the intensity of stress on the various parts of a continuous structure such as a tubular

**girder**, or the rib of an arch.The hogbacked

**girder**is a compromise between the two types, avoiding some difficulties of construction near the ends of the**girder**.The value of H is equal to the maximum tension on the bottom flange, or compression on the top flange, of a

**girder**of equal span, equally and similarly loaded, and having a depth equal to the dip of the suspension bridge.AdvertisementThe east side of the river (known as St Thomas's and Port Tennant) is approached from the west by a road carried over the North Dock Lock and the river by two

**girder**drawbridges, each of which has a double line of roadway (on which tramways are laid), two footpaths and a line of railway.A similar construction is followed for flat roofs, the grades being generally formed in the

**girder**and beam construction, and a flat ceiling secured by hanging from them, with steel straps, a light tier of ceiling beams. The floor beams are tied laterally by rods in continuous lines placed at or above their neutral axis.Showing a steel

**girder**bridge across the Mgeni River, probably near Pietermaritzburg.Then, turn around and you should see yet another

**girder**.Such a line has for abscissa the distance of a load from one end of a

**girder**, and for ordinate the bending moment or shear at any given section, or on any member, due to that load.AdvertisementWhen the load is at F', the reaction at B' is m/l and the moment at C' is m(l-x)ll, which will be reckoned positive, when it resists a tendency of the right-hand part of the

**girder**to turn counter-clockwise.Hence the moment of the load on Am at C is wy0m, and the moment of a uniform load over any portion of the

**girder**is w X the area of the influence curve Ip' G' E ' under that portion.Repeating the process for other positions, we get the influence line Aghb, for the shear at C due to unit load anywhere on the

**girder**.If the load is in the bay D'E' and is carried by a rail

**girder**which distributes it to cross girders at D'E', the part of the influence line under this bay is altered.Clearly, the distribution of the load by the rail

**girder**considerably alters the distribution of shear due to a load in the bay in which the section considered lies.The cost of the main girders for one span will vary nearly as the square of the span for any given type of

**girder**and intensity of live load.In 1883 an iron

**girder**bridge of five spans was opened, which carries the North-Western railway to Peshawar, and has also a subway for wheeled traffic and foot passengers.If the supporting member is a floor beam or

**girder**the**girder**should be rigidly connected to the floor system to prevent any twisting due to the weight of the projection.The arrangement of the building and floor framings is in a great measure governed by the architectural effect sought and by the arrangement and proper planning of the interior according to the intended uses; the positions of columns, girders and floor beams are usually the result of particular requirements, and unless complicated and expensive framing is to be expected the distance between columns must be kept within the limits of simple

**girder**construction.In case neither of the above methods can be applied, brackets should be used at each floor level or a continuous deep beam or

**girder**carried all around the building.The original bridge was strengthened in 1902 by the addition of a central steel

**girder**as part of a general capacity improvement program.He had in fact stepped onto a steel

**girder**pushed up against the rung of the ladder.The bridge is a big iron

**girder**affair, built in 1907 to replace a ferry.Reference 1 Inquiry into the basis of design and method of erection of steel box

**girder**bridges HMSO 1971 Interim Report.It is of steel

**girder**construction but still looks quite rustic because of its timber balustrade.The main

**girder**is then virtually a continuous**girder**hinged at the points of contrary flexure, so that no ambiguity can arise as to the stresses.The stiffening

**girder**, constructed chiefly of timber, was a box-shaped braced**girder**18 ft.The

**girder**held its position with both joints severed, proving that, as should be the case, there was no stress in the boom where the bending moment changes sign.The clear span is 790 ft., and the suspended

**girder**200 ft.The cantilever and suspended

**girder**types are as economical and free from uncertainty as to ' ??` the stresses.Roadster based frames are used as well as

**girder**forks with no extra bracing.Two halves of an arched

**girder**roadway support, bolted together with fishplates.This is due to the half weight of centre

**girder**, the weight of the cantilever itself, the rolling load on half the bridge, and the wind pressure.The centre

**girder**may be built on the cantilevers and rolled into place or lifted from the water-level.The

**girder**spans are 525 ft., the cantilever spans 547 ft., and the shore spans 201 ft.The Victoria Falls bridge over the Zambezi, designed by Sir Douglas Fox, and completed in 1905, is a combination of

**girder**and arch having a total length of 650 ft.It is formed by a crescent-shaped arch, continued on one side by four, on the other side by two lattice

**girder**spans, on iron piers.In such rolling operations the

**girder**is subjected to straining actions different from those which it is intended to resist, and parts intended for tension may be in compression; hence it may need to be stiffened by timber during rolling.If the bridge is erected when the river is nearly dry a travelling stage may be constructed to carry the projecting end of the

**girder**while it is hauled across, the other end resting on one abutment.Sometimes a

**girder**is rolled out about one-third of its length, and then supported on a floating pontoon.In the earlier

**girder**bridges the live load was taken to be equivalent to a uniform load of 1 ton per foot run for each line of way.Now let w1', w 2 ' be the

**girder**weights per ft.For a plate

**girder**bridge of less height than the train, the wind is to be taken to act on a surface equal to the projected area of one**girder**and the exposed part of a train covering the bridge.Next let the

**girder**carry a uniform load w per ft.The loads at D', E, due to unit weight on the rail

**girder**are (p-n)/p and n/p. The reaction at B' is {(p- n)xi+n(xi+p)}' /pi.In this connexion his most remarkable achievements were his railway bridges, especially those of the tubular

**girder**type.The great

**girder**bridges over the Menai Strait and at Saltash near Plymouth, erected in the middle of the i 9th century, were entirely of wrought iron, and subsequently wrought iron**girder**bridges were extensively used on railways.Bridges may be classed as arched bridges, in which the principal members are in compression; suspension bridges, in which the principal members are in tension; and

**girder**bridges, in which half the components of the principal members are in compression and half in tension.The immense extension of railways since 1830 has involved the construction of an enormous number of bridges, and most of these are

**girder**bridges, in which about half the superstructure is in tension and half in compression.So far as superstructure is concerned, more material must be used than for an arch or chain, for the

**girder**is in a sense a combination of arch and chain.On the other hand, a

**girder**imposes only a vertical load on its piers and abutments, and not a horizontal thrust, as in the case of an arch or suspension chain.But a main

**girder**may be supported at two or more points so as to be continuous over two or more spans.After various repairs and strengthenings, including the replacement of the timber

**girder**by an iron one in 1880, this bridge in 1896-1897 was taken down and a steel arch built _ _ __ _ I ?Rankine proved (Applied Mechanics, p. 370) that the necessary strength of a stiffening

**girder**would be only one-seventh part of that of an independent**girder**of the same span as the bridge, suited to carry the same moving load (not including the dead weight of the**girder**which is supported by the chain).There are two high-level footways for use when the bascules are raised, the main girders of which are of the cantilever and suspended

**girder**type.For spans over 75 ft., expansion due to change of temperature is provided for by carrying one end of each chain

**girder**on rollers placed between the bearing-plate on the**girder**and the bed-plate on the pier or abutment.It will be seen that the

**girder**directly rests on a cylindrical pin or rocker so placed as to distribute the load uniformly to all the rollers.In the girders of bridges the horizontal

**girder**is almost exclusively subjected to vertical loading forces.In some

**girder**-1 o bridges the members are connected entirely by riveting, in others the principal members are con nected by pin joints.There was an idea of using suspension chains combined with a

**girder**, and in fact the tower piers were built so as to accommodate chains.But the theory of such a combined structure could not be formulated at that time, and it was proved, partly by experiment, that a simple tubular

**girder**of wrought iron was strong enough to carry the railway.Though each

**girder**has been made continuous over the four spans it has not quite the proportions over the piers which a continuous**girder**should have, FIG.It would be economical, therefore, to make the

**girder**very deep. This, however, involves a much heavier web, and therefore for any type of**girder**there must be a ratio of depth to span which is most economical.At the cal culated position of one of the points of contrary flexure all the rivets of the top boom were cut out, and by lowering the end of the

**girder**over the side span one inch, the joint was opened - -- Section of Newark Dyke Bridge.By curving the top boom of a

**girder**to form an arch and the bottom boom to form a suspension chain, the need of web except for non-uniform loading is obviated.The top boom of each

**girder**is an elliptical wrought iron tube 17 ft.The depth of the

**girder**at the centre is about one-eighth of the span.Amongst remarkable American

**girder**bridges may be mentioned the Ohio bridge on the Cincinnati & Covington railway, which is probably the largest**girder**span constructed.The centre

**girder**has a length of 545 ft.The outer ends of the shore cantilevers are loaded to balance half the weight of the central

**girder**, the rolling load, and 200 tons in addition.In addition, an allowance is made for pressure on the leeward

**girder**according to a scale.A fundamental difference in

**girder**bridges arises from the mode of support.In addition, the hand railing on each side forms a

**girder**4 ft.