A treatise on architecture and building construction . rados having a horseshoe form, and the extrados apointed form. The example given shows the latter methodof construction. At a is shown the center for the horseshoeintrados; at b^ b are the centers for the pointed extrados ofthe arch; c indicates the soffit of the horseshoe arch; d^ theupper side of the arch ring; and e, the voussoirs. In allhorseshoe arches the center is stilted far above the spring-ing lines, to produce the required effect. 1)9. Arches having an elliptical or oval form, or pointedin the center and elliptical near the spri
A treatise on architecture and building construction . rados having a horseshoe form, and the extrados apointed form. The example given shows the latter methodof construction. At a is shown the center for the horseshoeintrados; at b^ b are the centers for the pointed extrados ofthe arch; c indicates the soffit of the horseshoe arch; d^ theupper side of the arch ring; and e, the voussoirs. In allhorseshoe arches the center is stilted far above the spring-ing lines, to produce the required effect. 1)9. Arches having an elliptical or oval form, or pointedin the center and elliptical near the springing joints, areoften used in architectural work. These may be formedeither of true elliptic curves, or of 3 or 5 centered circulararcs. Very flat elliptical arches are not suitable for anyconsiderable span, and, if built, should have large piers orabutments; or beams may be placed above the arch, torelieve it of some of the load. The method of finding the direction of the joints in a falseelliptical arch is shown in Fig. 54. The construction of the. ellipse is similar to that given under the heading, InvertedArches, Masonry, §7. The radius for the middle of thearch is a b; the radii for the two haunches are the lines c d. 8 MASONRY. 55 The joints of the voussoirs in the central portion are drawnwith a as a center, as at cc, etc.; and the joints for thehaunches are drawn with c, c as centers, as at ff, etc. 100. A method of finding the voussoir joints in a trneelliptical arch is given in Fig. 55. This shows d\ d\ d\ d\
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