. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. 214 Tllli CIVIL ENGIx\ AND ARCHITECT'S JOURNAL. [July. though felt, and to « certain degree acted upon, has not hitherto admitted uf a clear explanalioo. The annexed diagrams, Hgs. 18 and 19, exhibit forms of arches, supposed to be loaded a material of equal weight with the aroh, and show the necessary to sustaiu them. In these, it will be observed that \ \ \ \ """ââJ \ \ \ \ "^^^^^ \ \ \ â -^ \ Fig. 18. Fig. 19. the division between
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. 214 Tllli CIVIL ENGIx\ AND ARCHITECT'S JOURNAL. [July. though felt, and to « certain degree acted upon, has not hitherto admitted uf a clear explanalioo. The annexed diagrams, Hgs. 18 and 19, exhibit forms of arches, supposed to be loaded a material of equal weight with the aroh, and show the necessary to sustaiu them. In these, it will be observed that \ \ \ \ """ââJ \ \ \ \ "^^^^^ \ \ \ â -^ \ Fig. 18. Fig. 19. the division between the arch and the abutment is not made where the arch, so called, commences. The point of division adopted, has not been chosen on account of the result as to the required thickness of abutment being materially affected by it; but as being the place at which rupture would ensue, if the abutments yielded. In fact, the effective part of an arch is only so much of it as would not stand unless the arch were entire. So much of the arch as lies below this point, would stand of itself, and is practically a part of the pier or abutmt-nt, curved out for the arch to spring from. This point of division also permits a readier means of computing the thickness of abutments; as with the exception of the small projection at the springing, the weighi of which may be omitted, the abutment is a rectangle, when the roadway is horizontal. In this manner the following formula is derived, for ascertaining the thickness of the abutments necessary to support a given arch ; the height of the abutment being KVC Kig. 20. If B EF (lig. 20) represent the half arch with its backing, and G is the centre of gravityâassuming ;; and ;/to be two points of application of the pressure, or points in the curve of equal horizontal thrust in the archâ let;;/=d, kf=h, p q â m, p r = n, A U = a, «⢠= weight or area of arch and backing, and x ^ D C the width of abutment sought; then assuming equal are
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