Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

181 OF ENGINEERING FORMULÆ. BracUd Arches. Determination of Equilibrium Line by Graphic Construction. For notation see preceding page. 1st. Lay off from crown of arch tangent B D, , . , W y making k = - • 1 H 2nd. Find position of centre of gravity;</ = —. 3rd. From G (the point of intersection of the vertical line passing through the centre of gravity) draw the horizontal line G a — H, to any convenient scale. 4th. Through a draw the vertical line T a e, making T e = total load on half arch = W. 5th. On the line Te lay off T b, b c, c d, de — w w; wtll respectively. 6th. Join b G, c G, d G, e G ; the length of these lines represent the intensity of stress on the lines drawn parallel to them. 7th. Draw to the intersection of the vertical lines of load Bo, on, nm, m I, and I e, parallel to GT, Gb, Ge, Gd, Ge, respectively com- menced at B. The line I e should pass through the point 0; this checks the accuracy of calculation and drawing.