Variable-radius Bends

AISC Design Guide 33 Curved Member Design Section 2.2.6

Parabolic, elliptical and other non-circular bends are variable-radius bends, also known as multi-radius bends. The funicular form for a member resisting a uniform gravity load is defined by a parabola; therefore, many arches are shaped to a parabolic curve. Elliptical bends can be required where a curved plane interfaces with a skewed plane.

When bending materials to an elliptical or parabolic configuration the radius of the bent section will be changing throughout the arc (or bent section) and stay in one plane. Typically, a bending company would require various working points (rise locations) of the elliptical curve to successfully bend the section. For certain projects Albina will create a full-scale layout on the ground to QC / match the elliptically bent section. At times Albina will also use digital templates in conjunction with a sophisticated camera system to ensure the accuracy of the elliptical or parabolic bends. These methods identify where the part is within and potentially outside the agreed upon tolerances (working points).