John L Culley
Published: 2013-09
Total Pages: 20
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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1886 edition. Excerpt: ... allel to H 1 andK 2, which would cause an outward movement in these triangles; which would be greatest at or near the point J and L. When the angle of obliquity H J 1 or K L 2 is very acute, neither the bond or the strength of the voussoirs will resist the tendency to rupture, nor would the friction of the bedding surfaces produced by the weight and load of the voussoirs prevent the outward movement at J or L, and the arch will fail from sheer weakness. 25. It is true that small oblique arches, with their coursing joints parallel to their axles, are often with safety built. Their stablity is due to the fact that as ordinarily constructed the depth of their voussoirs is in excess of what economy would in larger arches dictate. In other words, the voussoirs maintain their position by virtue of their large bedding frictional surfaces. If, however, economy or other consideration should require their depth of ring to be minimum, or if the parts H J 1 and L K 2 were loaded anything like the body of the arch is capable of sustaining, the smaller like the larger arches would give away. 26. It is evident that to maintain the stability of an oblique arch it is desirable that its stress and thrust should be conveyed to the abutments in planes parallel to the oblique faces of the arch, or as near so as is possible, and also that this object cannot be attained when the coursing joints are parallel to the axis of the arch. The coursing beds to fully realize this condition should be normal to the oblique faces of the arch wherever they come in contact with them. 27. There are three methods in vogue that closely approximate this requirement. They are known as the Logarithmic, the Come de Vache, or Cow's Horn, and as the Helicoidal Methods. Without...