The Top 5 Common Questions about Jumbo HSS
Now that Atlas Tube has introduced Jumbo HSS (hollow structural sections) to North America, we’re finding a lot of people have questions about HSS — and when and where they should be used. This week, we’ll attempt to answer the five most asked questions:
What are the available sizes and how available are they?
The Jumbo HSS sizes, produced by NSMP and distributed by Atlas Tube, can be found here. Atlas Tube and its partners will be stocking material here in the US. Mainly the square sizes will be regularly stocked. Having the square sizes in stock at various locations in the U.S. will mean these sizes will be as readily available as the most common HSS sizes currently available in the US and Canada.
To which specifications are the Jumbo HSS produced?
The Jumbo HSS are produced such that they meet several of the most common international HSS specifications. In North America, these specifications are ASTM A500 and CSA G40.
How are Jumbo HSS different from HSS currently available in the U.S. and Canada?
There really is no difference between Jumbo HSS and other HSS. They are both made from high-quality steel in a high-quality manufacturing process. The main difference is that the Jumbo sizes are bigger and have not been readily available in North America before now. The other difference is that you can use the nominal thickness as the design thickness. This is because the Jumbo HSS meet the CSA G40 specification, which has tighter tolerances than the ASTM A500 specification. Therefore, you do not need to apply the .93 factor to the nominal wall thickness for HSS produced to ASTM A500.
Are the Jumbo HSS sizes listed in the AISC and CISC steel manuals?
Currently, the Jumbo HSS design properties are not listed in either the AISC Steel Construction Manual or the CISC Blue Book. However, they are listed on both of their websites (provide both links). In addition, AISC has created column load tables in the dual ASD / LRFD format. These tables can be downloaded on AISC’s website.
In what type of applications should one consider using Jumbo HSS?
- Tall, unbraced columns: Jumbo HSS are suitable as columns with large loads and long, unbraced lengths. Consider building projects with tall story heights where a minimal number of columns is desired, such as large, one-story distribution centers, grand lobbies of commercial office buildings, and hotels and convention centers.
- Long-spans: Bridges and large roof structures can span further using the Jumbo HSS sizes. Long-span roof trusses can take be more aesthetically pleasing when using Jumbo HSS over built-up or wide-flange sections.
- Concentric bracing in seismic zones: Several of the Jumbo HSS sizes meet the seismic compactness (width-thickness ratios) criteria given in the current AISC Seismic Provisions (AISC 341). This allows the continued use of square HSS sections, which have traditionally been used in concentric bracing systems.
Parking garages: Steel parking garages are becoming more common and cost-effective. There are many advantages to using Jumbo HSS as the columns in a steel parking garage. You can minimize the number of columns used because of their greater axial capacity, leading to fewer columns to interfere with parking spaces. The lower surface area of HSS, versus a wide-flange section, means lower coating / painting costs, which can be a major cost item in steel parking garages.
- Rigid frames: Jumbo HSS used as the columns (and perhaps even the beams) in rigid moment frames can be a cost-effective alternative to traditional rigid moment frames. These have become the system of choice in Japan when designing to resist high seismic loads. Moment connections have always been the challenge when using HSS in rigid frames. Companies such as ConXtech and SidePlate Systems have started to look at providing cost-effective solutions to this type of connection.
- Robust structures: Some projects today require a higher level of security, which also means a more robust structural skeleton. Redundancy, blast resistance and design against progressive collapse have all become part of the design landscape in recent times. Jumbo HSS are now another tool to be used in accomplishing a more robust structure. To even further enhance this capability, one can fill a Jumbo HSS with concrete and design the columns as concrete-filled tubes (CFTs). Watch this space for more on CFTs.
So there you have it: some answers to the common questions out there about Jumbo HSS. If you think of a question not addressed here, please do not hesitate to contact me at firstname.lastname@example.org, and I will work to answer it.
Now that you have all the answers, shouldn’t you be out there designing the next great structure using Jumbo HSS?