In the realm of structural engineering, the significance of connections cannot be overstated. They are the glue that holds steel structures together, providing not only stability but also the crucial ability to transmit loads effectively.
Let’s take a closer look at what is behind the whole area of HSS structures. Which sections are HSS? All the types that are not open (that was quite easy, right?).
Standard HSS shapes: What tube arsenal is available for a structural engineer's design?
Use of HSS members: We can use HSS members everywhere, but the most common applications are:
How are the tubes made?
The tubular members are manufactured in two different ways:
- Colled-formed / rolled + welded – the tubes are created by bending sheet metal into the required shape and then welded into the closed section.
- Continuous milling – the basic material is heated to white-hot and molded into a cylinder and then a bullet-shaped piercer point is pushed through.
Advantages of HSS members
What are the maximum standard sizes available these days?
An answer could be found in the new world’s largest continuous ERW mill just recently built in Chicago as the pride of US steel pipe and tube manufacturer Zekelman Industries. Until now, the maximum HSS size provided in the US was 16″x16″x5/8″ (406x406x16 mm).
In this new mill, they increased the maximum tube sizes up to:
SHS – 22″x1″ (559×25 mm)
RHS – 34″x10″x1″ (864x254x25 mm)
CHS – 28″x1″ (711×25 mm)
Disadvantages of HSS members
Design codes and manuals dealing with HSS connection design - main regional guidelines:
Advantages of HSS connection solved in IDEA StatiCa
For multiplanar hollow section connections, the designer applying the code provisions needs to make assumptions-heavy approximations in order to calculate them, while there is always the danger that there are configurations that are simply not covered by the code provisions. One such example is the bird beak type of connection, especially when the incoming members are in sections.
The underlying CBFEM model from IDEA StatiCa can safely be extended to calculate multiplanar hollow section connections while maintaining the same level of accuracy as in the case of uniplanar hollow section connections. Even the bird beak type of connection can easily be modeled and calculated without requiring any special action to be taken by the designer.
What tools can be used for HSS connection design?
The HSS connection design and analysis couldn’t be precise enough without the GMNA (geometrically and materially nonlinear analysis)that can calculate even the most challenging case with slender walls governed by high local deformations. What was it developed for and when to use it? All the necessary information is summed up in one of the previous blog posts dedicated to this topic, below.
If you’re looking for some inspiration for circular hollow sections, you could be interested in these webinars dedicated to CHS bracing member connection and to 3D multimember connection combining CHS and SHS profiles.
In order to get a better understanding of Sample Designs and Case Studies relating to HSS to HSS connection, please click here.
In a recent article by the Steel Tube Institute, which focuses on contemporary software tools for HSS connections, a comprehensive examination of various connection design applications in the market was conducted. The IDEA StatiCa Connection app stood out prominently as the sole tool rooted in the FEA method, enabling it to model a wide range of connection topologies. Additionally, this overview identified IDEA StatiCa as the sole tool that met all the assessed criteria.
What kind of obstacles can appear during the design?
Quite often overlooked mistakes or imperfections in design could be caused by missing checks for hollow member local buckling failure. For users of IDEA StatiCa Connection, this is an easy task since there is a simple check box embedded in the setup dialog. With this feature turned on, the local deformation check is contained by the connection analysis.
Besides the local deformation issue, we can find there is an important difference between the failure modes of thin-walled and standard hollow section members:
(red line – thin-walled members, green line – standard members in compression, blue line – standard members in tension)