Arch & Curve Setting-out

I know

Span mm Rise mm

Ordinates each side Voussoirs (bricks) in the ring Ring depth mm

Span is the chord between the springing points. Rise is the height of the crown above the springing line. A rise of half the span is a semicircular arch; the rise is limited to that. Ordinates are measured up from the springing line at set distances from the centre line.

Radius–

Arc length–

Span / rise–

Centre below springing–

Arch elevation

Setting-out ordinates from the centre line

x from centre	y above springing	from springing end

Arch & Curve Setting-outGive any two of span, rise, radius or arc length. Get the radius, the centre point, the arc length and a table of plumb ordinates for pegging the curve on site, with the voussoirs drawn.

Arch elevation

Setting-out ordinates from the centre line

Working every step