Although the automotive industry shapes people’s thought of United states manufacturing, and metal manufacturing especially, it isn’t the nation’s largest consumer of metal-not by way of a long shot. It’s commercial construction.
To decrease cost, builders have relied on design strategies to reduce the volume of hollow section steel tube a structure needs, in addition to reduce on-site erection time. One design avenue that has become considerably more popular within the past two decades has been to utilize alternatives to the standard wide-flange beam.
These beams have evolved into an effective building material of preference. But in relation to strength, the form in the wide-flange beam pre-sents challenging. It can span simply a certain distance (or “unbraced length”) before requiring support. Coming from a purely strength perspective, it will be a lot more efficient for beams to use on a circular, square, or rectangular shape, which will extend the utmost unbraced length. The more distance these structural members can span, the fewer braces and supports a building needs. Ultimately, what this means is builders may use a smaller amount of what’s often their biggest expense: the structural metal itself.
Enter hollow structural sections, or HSS (see Figure 1). These round, rectangular, or square tubes have shapes which provide inherently higher strength and will span greater lengths between braces. A square steel tube having a 3/16-in.-thick wall thickness has an allowable load of 79 kips across a column time period of 32 ft., while a similar wide flange (ASTM designation of W12 x 40) has an allowable load of 64 kips on the same column length (see Figure 2).
For decades HSS have already been utilized for their dramatic effect. Builders and architects used those to make an artistic statement, not to spend less, which remains true in many cases today. But because HSS are really strong, architects can design buildings with less material. HSS also save money on finishing costs, because compared to hollow section tube, tubular sections have less surface area to color or fireproof. Combine this with the truth that tube production costs have fallen in recent years, and building with HSS actually starts to make real economic sense. This is certainly one primary reason that interest in HSS continues to be rising because the recession, and it’s in this environment that the tube cutting laser is starting out open up new opportunities.
HSS represent a departure from many tube laser cutting applications that tend to use relatively thin-walled workpieces. Shops providing HSS often must cope with workpiece weights (called “stick weights”) up to 2,000 pounds. These workpieces are not only long, and also large; 14-, 16-, and 20-in. diagonal cross sections aren’t uncommon.
To create such large workpieces cost-effectively on a tube laser requires meticulous planning. It’s a lot more complicated than employing a cutoff saw, it also adds considerably more value to the workpiece. Modern tube lasers have load/unload functions that may handle mill-length pipe and structural material.
This capability gives designers seamless steel pipe when it comes to designing for mated sections. Mating a round tube to another round tube seems simple, nevertheless the bevel required dexopky12 develop a tight fit-up involving the two sections can be very complicated, particularly when tubes are of different diameters or shapes, or if they intersect at unusual angles.
From an architectural engineering perspective, such angles may make the best transfer of loads and many efficient usage of HSS. But to the welder and fabricator, this type of complicated joint can be a nightmare.