Discussed in a previous blog from last year, an Ohio state park committee was seeking curved steel 20×4 tube stringers for a monumental outdoor stairway. The problem the committee ran into was that the size tubing the design team had decided upon was not produced in the weathering steel which was an essential component of the design. So the decision was made to construct the tube stringers out of 1/2 inch flat sections 4” and 19” in width to create the walls from readily available material. This would require care and precision by an experienced plate roller in order to insure each section of the built-up rectangular tube would match up to make both inside and outside tube stringers.
The plate roll operators labeled each section in order to assist the fabricator with the assembly of the stringers. Once they arrived at the fabricator, the steel stringers would need to be assembled with slight variations in radius and pitch between the inside and outside tube walls. Ensuring these were matched up properly with the pair of 4 inch wide flats to be welded would require a great deal of work. To assist in this, the fabricator installed spacers between the 19 inch walls to ensure a consistent hollow cavity space in the rectangular tube.
In the end, the fabrication of the helical tube stringer was only one portion of the complexities of this job. The pieces needed to be brought to the jobsite and installed in a location that you could certainly call out of the ordinary. As seen in the photos, the final installed staircase has become a beautiful addition, contrasting with the natural surroundings and leading visitors of the park up for a closer view of the nearby waterfalls.
The end result, is that some jobs that may call for a helical tube stringer which is out of the ordinary, or perhaps beyond the capabilities for traditional rolling techniques. However locating a bender/roller with experience in constructing challenging helical staircases can offer alternatives that may be previously not considered, and result in an equally beautiful project utilizing rolled plate.
