October, 2023- Guest Editorial: A NEW WAY TO LOOK AT BOLTS
Most fabricators will admit a field welded connection isn’t their first choice. And who could blame them? Field welds are labor-intensive, hazardous, difficult to inspect and can slow a project’s timeline considerably. Given the option, most fabricators will choose to bolt.
But bolting has its drawbacks too, namely the need to reach both sides of a connection, which has led to slower adoption of hollow structural sections (HSS) in the U.S. construction industry. Though HSS columns have better strength-to-weight ratios than wide-flange equivalents, the inability to make a bolted splice has rendered them almost completely absent from multi-story construction in the U.S. Shuriken, from Atlas Tube, is a product designed specifically to enable bolted HSS splices and other one-sided connections with standard hardware.
RETHINKING WRENCH DESIGN
Shuriken is similar to a single-use socket wrench. In the shop, it can be installed on splice plates, and those splice plates are then inserted into one side of the HSS being spliced. Then in the field, the two lengths of HSS are mated; bolts are inserted and pretensioned from the exterior.
Atlas Tube was a good fit to take Shuriken to the mass market. The company recently opened the world’s largest HSS mill in Blytheville, Arkansas, and has been looking for ways to increase HSS use. Shuriken reduces the overall installed cost of HSS columns by eliminating welded splices, making it a natural complement to the Atlas Tube product line.
Shuriken is not the only way to bolt HSS connections nor the first to try to tackle onesided bolting in general, but earlier solutions have proven to be awkward, bulky or hard to fabricate. Instead of focusing on the bolts themselves as a solution, Shuriken redesigned the wrench. This approach has a few notable benefits: the bolts are standard A325 or A490 bolts; the nuts are standard A563 nuts; it’s installed over a standard hole; and the bolts can be fully pretensioned, allowing the use of slipcritical connections.The use of standard materials and procedures makes it easier for engineers and fabricators to incorporate Shuriken into their projects.
While Shuriken’s features were designed from the beginning, the variety of applications have yielded some surprises. Customers have come to Atlas Tube over and over with clever applications that never crossed the minds of the company’s engineers. Some of these have been specific to that customer’s project, while others have made it into the Shuriken typical detail set. That set now covers a wide range of connections, including HSS splices, HSS shear and moment connections, HSS truss connections, and other connections unrelated to HSS, such as obstructed beam connections.
Perhaps the most exciting application on the horizon is SpeedCore, a composite alternative to reinforced concrete building cores that replaces both the rebar and formwork with a pair of joined steel plates that form the two faces of the wall. The steel panels are then filled with concrete following erection. Up until now, all the joints in SpeedCore projects— which can measure in miles for a single building—have been field welded.
STAY ON SCHEDULE
Shuriken presents an opportunity to compress high-rise construction schedules even further by eliminating those welds. AISC has been supportive of research concerning bolted SpeedCore connections and is currently supporting two research projects that test SpeedCore joints bolted with Shuriken at the component and system levels. To date, the SpeedCore system has been used in projects in Seattle and San Jose, cutting months from the schedule in each case.
The Shuriken team is working to expand the size range, which currently comprises ¾ in., 7/8 in., and 1 in. bolts, to include smaller and larger sizes to broaden the range of applicable connections. They also have plug-ins for SDS2 and Tekla to help detailers incorporate Shuriken into their projects more smoothly.
“The reception we’ve had is fantastic,” says Brad Fletcher, a senior sales engineer with Atlas Tube. “Each time Shuriken gets used on a project, the engineer, fabricator and erector all become familiar with the product, and they take that knowledge to the next project.”
Ted Goldstein, P.E., is the inventor of Shuriken and now the Shuriken Business Development Engineer for Atlas Tube (http://atlastube.com/shuriken ). Ted worked for eight years as a structural engineer in New York before moving to Japan in 2018. There, he was inspired to create Shuriken to reduce the cost and carbon footprint of steel construction.
