ABSTRACT
Bridges constructed of brickwork or masonry are built in the following manner: the span of arch or arches and their rise and radius are determined upon ; from these the depth of the arçh may be obtained by employing Rankine’s formula given in the chapter on Graphic Statics. A barrel vault consists of a continuous arch, resting upon the side walls of a building, which must be very thick in order to resist the thrust of the vault which is distributed along the whole length of the vault; the Walls thus become in effect continuous buttresses. A dome is a roof of the form of a semi-spheroid, ellipsoid, or conoid. The dome is more often supported upon walls square or octagonal in plan, but any other regular polygon would apply equally well. The effect of this, especially where the secondary vaults are large, is to concentrate the pressure of the vaults upon sections of the walls.
