. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. the whole must fall together. In fact, the structure is no securer than a child's house of cards. It is very true, that if the platform be made perfectly rigid it can never assume the position of the second diagram. But then if it have this rigidity it becomes a girder-bvidge, and the increased strength of the main chain requisite lo support the increased weight of the girder would be so great, that it would be belter to dispense with the chains altogether, to unite the two i
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. the whole must fall together. In fact, the structure is no securer than a child's house of cards. It is very true, that if the platform be made perfectly rigid it can never assume the position of the second diagram. But then if it have this rigidity it becomes a girder-bvidge, and the increased strength of the main chain requisite lo support the increased weight of the girder would be so great, that it would be belter to dispense with the chains altogether, to unite the two independent girders which we suppose banging over the river, and when they are connected at the centre, to let the whole rest upon abutments on either bank. The |only bridges which we have of Mr. Dredge's, those in 'the Ee- gent's Park, certainly have not the rigidity of girder bridges : they have quite pufticient flexibility to produce the etlect explained above, supposing they were divided at the centre. We do not tliiuk that any one who has seen them, except, perhaps, the inventor, would like lo stand on them while the experiment was being made. It is to be remembered, that the bridge at Calcutta gave way by break- ing at the centre, Ou the whole, therefore, it seems clear, that Mr. Dredge's system of lessening the thickness at the chain at the centre has a limit. We are convinced that no practical engineer of reputation would consent to con- struct a suspension bridge without a very ample provision in this re- spect. The other distinguishing feature of Mr. Dredge's invention is the obliquity of the suspending rods. On this point we will not speak posi- tively, but our present impression is, that this arrangement does not permit any saving of material in the main chain. On the contrary, it seems that the obliquity of the suspending rods demands a greater strength iu the main chain than would otherwise be required. Our reason for this opinion is as follows, though it is tu be
Size: 2225px × 1123px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., boo, bookcentury1800, booksubjectarchitecture, booksubjectscience
