Page 38 - Modern Steel Construction (April 2019)

Curved steel components are a structural highlight of The Spheres in steel. When a shape has been curved successfully, the
downtown Seattle. strains the member will experience under actual service
conditions will be much smaller than those associated
with the curving operation. Once the curving is done, the
member can be expected to perform as needed.
Is curving steel a better option than creating the
appearance of a curve with multiple segments?
As noted previously, it’s less costly to curve a length of
material versus miter cutting and welding multiple seg-
ments to achieve the appearance of a curved assembly. In
addition, a continuous curve facilitated by the bending
process appears much smoother than a segmented assem-
bly made from multiple sections. Bottom line, curved steel
looks better than a “faked” curve.

What items will a bender-roller ask you for when you
approach them with a curved steel project?
For starters:
• Your overall vision for what you want to bend
• Member shapes and sizes and material type to be bent
• How the members will be oriented
• Correct nomenclature to match what is drawn
(i.e., “inside radius”)
• AESS requirements, if any, for the curved members

Diving deeper, what details should designers include
on curved steel documentation for bender-rollers?
Since a curved member’s size and specified radius
will determine how a bender-roller will approach
the forming operation, and ultimately determine the
process and machine used to form said member, it is
extremely important to accurately convey as much
detailed information as possible on curved members in
the architectural and structural documents in order to
get the most accurate cost for what is typically referred
to as the “curved/formed metals package.”
Many construction projects if not all, release structural
and architectural prints for the general contractors and
subs to bid on. A vast majority of these prints contain-
ing rolled members do not contain the necessary details
needed to accurately calculate the costs of producing
formed members. A properly detailed print contain-
ing rolled members should always detail radius and arc
length, along with the proper section views to determine
the orientation that the member is rolled or formed.
Many times, this lack of information has forced subcon-
tractors to speculate on the curved member’s radius and/
or to scale the rolled member from other members on
the print and use that information to make a best guess
at the radius. The result is that what was bid/quoted is
not what was needed or intended to be conveyed by the
design documents provided. This can cause major delays
and cost increases for a project, especially when it hap-
pens mid-fabrication/erection.
What’s the best way to bend steel?
Several factors determine the best technique, including
the overall member size, web and flange thickness or HSS
wall thickness, radius requirement and end application

38 | APRIL 2019