原创 Abercrombie Outlet417

Abercrombie Outlet417

It is very easy to see that if CV is an arch of 60°, and V v is ^th of VC, the points ? and c will be on a level; for the secant of CV is twice CO, and therefore C c is 8 times V t> which is $th Gf VH.
Tne line vgcf is drawn according Abercrombie to this calcu?lus or construction. It falls considerably b^low the horizontal line in the neighbourhood of c; and then,passing very obliquely through c, it rites rapidly to an unmeasurable height, because the vertical line through A is its assymptote. This must evidently be the case with every curve which springs at right angles with a horizon?tal line.
It is plain that if v V bjp greater, all the other ordinates of the curve vgcf% resting on the circumference AVE, will be greater in the same proportion, and the curve will cut the horizontal line drawn through v in some pctint nearer to t? than cis. Hence it appears that a circular fcrch cannot be put in equilibrio by building on it up to k horizontal line, whatever be its span, or whatever be tfii thickness at the clown. We have seen that when thil thickness is only T*7 of the radius, an arch of 120 degrees will be too much Abercrombie and Fitch Outlet loaded at the flanks. This thickness is touch too small for a bridge, being only of the span CM, Whereas it should have been almost double of this; to bear the inequalities of weight that may occasionally be oh It. When the crown is made stilf thinner, the outline Abercrombie and Fitch is still more depressed before it rises again. There is there?fore a certain span, with a corresponding thickness at the crown, which will deviate least of all from a horizontal line. This is an arch of about 54> degrees, tbe thickness at the crown being about one-fourth of the span, which is extravagantly great. It appears in general, therefore, that the circle is not a curve suited to tbe purposes of a bridge or an arcade^ which requires an outline nearly horizontal. It follows from this investigation, that the hack or e* trados of a parabolic arch of equilibration must be parallel to the arch or soffit itself; or that the thickness of lbs Abercrombie Outlet arch, estimated in a vertical direction, must be equal throughout; or that the extrados is the sau)e parahoU with the soffit or intrados.