Excel Engineering Wins 2024 CFSEI Creative Detail Award for DNS Capital Project in Chicago

All photos courtesy of Excel Engineering.

E & K of Chicago contacted Excel Engineering, Inc., Fond du Lac, Wisconsin, about designing a unique staircase for the DNS Capital project in Chicago, Illinois.

E & K sent Excel Engineering the hand sketch shown in Figure A. The sketched showed a curved staircase, which the architect wanted constructed out of cold-formed steel (CFS) framing members. After reviewing the sketch, Excel Engineering designed a stable and constructible “H” frame CFS system.

The project received the Creative Detail — Second Place honor in the 2024 CFSEI Awards presented by the Cold-Formed Steel Engineers Institute.

Hand sketched drawing of a curved staircase to be built with cold-formed steel (CFS) framing for the DNS Capital project in Chicago.

The challenge was designing a curved stair that could be easily built using straight, CFS members.

Stable ‘H’ Frame Design

Excel Engineering’s goal was to design a series of straight metal frames, fanning them out like the spokes of a wheel. Since this would be a free-standing set of stairs, the frames needed to be stable.

The Excel Engineering team designed an “H” frame for each step — with a diagonal underneath to resolve the stability in the sideways direction as shown in Figure B.

Excel Engineering used the sheathing to stabilize the forces in the direction up/down to the steps. The vertical portions of the “H” would resist the weight and cantilever up to form the handrails.

Excel Engineering designed a cold-formed steel (CFS) “H” frame for each step in the curved staircase, adding a diagonal CFS bracing stud underneath each step to provide sideways stability.

Field Measurements Eliminated

The staircase contained a total of 18 steps, each step having 4 corners. To locate one corner of a step, the Excel Engineering team took an X, a Y and a Z measurement.

18 steps x 4 corners x 3 dimensions = 216 field dimensions

The Excel Engineering team asked these questions:

• To build the curved staircase, wouldn’t we want as few field measurements as possible?
• Can we creatively eliminate some or all the field dimensions?

The team decided to have the drafter elevate each “H” frame step with dimensions. This way the 18 steps could be prefabricated off site. Thus, elevations were drawn for each step.

But how could the Excel Engineering team eliminate the X and Y measurements?

The only way to eliminate these dimensions would be to print a life size floor plan. That’s exactly what the Excel Engineering team did.

The Excel Engineering engineer printed a life size floor plan for the contractor. The plan required four, 3’-0”-wide sheets of paper to print.

The E & K team took no X and Y field dimensions in constructing the curved staircase, since all the steps were printed on the life-size plan.

Using a large-scale printer, which could print 3 feet wide by 20 feet long, the specialty engineer printed a life size floor plan indicating Step 1 through Step 18. The engineer also printed the stud profiles for all vertical portions of the “H” frame.

However a problem arose. The specialty engineer designed all “H” frames with 1-5/8” flange studs. The printed plan revealed a conflict with several of the vertical members of the “H” frame, which was created by the tight stair corner.

This was resolved by designing the frames with a smaller flange – 1-3/8” flange steel studs solved the issue, as shown in Figure C. The engineer reprinted the plans using 1-3/8” flange CFS studs, and the system fit snug with no conflicts.

Life-Size Printed Plans

The life-size plans were shipped to the site in a cardboard tube. The E & K team laid out the life-size plan, taped it to the floor and then, stood up the vertical portion of the Step 1 “H” frame. They aligned the frame with the Step 1 printed profile and bolted them to the floor. Then, they stood up the Step 2 “H” frame, aligned it with the Step 2 printed profiles and bolted them. And so on.

No X and Y field dimensions were taken, since all the steps were printed on the life-size plan. Pictures D and E show the paper profiles on the floor and the as-built results.

Excel Engineering shipped the life-size plans to the site. E & K taped the plans to the floor, aligned the Step 1 “H” frame with the Step 1 printed profile, bolted the frame to the floor, and so on with each step.

E & K did an amazing job constructing this project. Excel Engineering found them to be a joy to work with. Read the complete story and obtain the complete design diagrams for Excel Engineering’s 2024 CFSEI Creative Detail Award here.

Additional Resources

• eBook: Specifying Cold-Formed Steel Framing: A Guide for Architects and Engineers
• 2023 SFIA Awards: 7 Key Learnings about Using Cold-Formed Steel (CFS)
• SFIA Reveals 7 Winners of the 2023 Industry Project Awards in Online Ceremony