Multi-Radius Bending of Pipes for the CTA Yellow Line, Oakton Station, Skokie

The bending of pipes and tubes can contribute to the aesthetic value of a project.  For example, currently under construction, the Skokie Oakton Station is already exhibiting its “beautiful canopy of architectural steel arches” according to the Swift Updates Newsletter.  “The Village of Skokie and project partners are pleased with the progress thus far . . . . “  The station is an island platform between the rapid transit rail lines running north and south.

A project like this does not happen without considerable planning.  Our involvement as a bender/roller began very early. The architecture firm contacted us for budgetary pricing of the curved elements of the structure.  The entire project was to be funded, at least in part, by a $10,200,000 federal grant promoting traffic congestion relief and cleaner air quality.

We were next involved when we were contacted by various structural steel fabricators who asked us to bid on the curved steel which included a complicated elliptical shape made out of 6in pipe.

The architect and engineer supplied the steel fabricators and us with drawings including x-y coordinates for multi-radius bends.  Once the contract was awarded to the steel fabricator, they put these x-y coordinates into their shop drawings and discovered that the multi-radius arcs were not tangent to one another.  If the sections were curved according the points, there would be kinks rather than smooth transitions between the different radii.  We worked with the detailer and architect to redesign the project by simplifying the radii to achieve the overall height and length while keeping the transitions smooth.

The elliptical roof supports are composed of 6in pipe, each one rolled to two radii from as tight as 47in center line radius and as large as 240in center line radius.


The structural members on top of the 6in pipe are composed 45 sections of curved 10 x 4 rectangular tubing rolled the hard way (x-x axis) to a 34ft radius. These tubes support the metal decking.

268,000 lbs. of curved steel sections contributed to a beautiful steel structure that will be the pride of Skokie.

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