Tees are not a typical steel section that mills produce. Almost all steel tees have to be created by splitting I-beams. Mills typically generate Tees up to 2.5” X 4.6 lbs/ft but once they become larger than that they have to be made by splitting I-beams. The web of the beam can be split by either Continue reading Curving or Straightening Steel Tees
Can you imagine living in a home larger than the airplane hangar for a 747? Well David and Jackie Siegel are about to finish construction on their 90,000 square foot residence. David Siegel, the billionaire founder of Westgate Resorts, started construction on this mega-mansion in 2004 and after the financial crisis in 2008 had to take a hiatus from funding this build. The home, which is just now coming to fruition, includes a 30 car garage, 2 movie theaters, and around 800 tons of structural steel.
The house is modeled after the Palace of Versailles in France and features a copious amount of windows, around 2000 in fact. To match the Arched French windows and doors highlighted on the French Palace, the architects incorporated numerous French arches into the Florida residence.
When architects are designing a house with this many windows they must keep in mind a key component of construction, the lintels. A lintel is a structural horizontal block that spans the space or opening between two vertical supports. Lintels are not only load-bearing building components, they can also be decorative architectural elements.
Lintels can be made out of a variety of materials. Steel lintels are the most reliable and versatile. When using steel you have the option to use any number of different shapes. The shape and style of a lintel can be manufactured to best suit the building material and window style for your project. Frequently, lintels are made using curved steel angles, or rolled tees. The design of the Siegel residence called for curved lintels over many of the windows and doors. These specific lintels were used for structural support and for decorative purposes. The style shown here is made with curved steel and this is just one of many different types of metal lintels that are possible.
Arched Lintels are also important for safety purposes. Brick arches that are installed without lintels can be weakened over time and sometimes even collapse. Nobody wants to be around falling bricks and archways. So whether you are building a home with 2000 windows or merely 2 windows, you should always consider which type of lintels you are using.
The splitting tolerance was +/-1/8in; the rolling tolerance was +/-1/8in on the rise over 10ft. (Tighter than the 1/8 over 5ft AISC tolerance for straighness.) Beyond these tolerances, what was critical to the application was consistency of the outside radius measured at the tip of the stem and that the tees be as equal as possible.
Measuring the radius of a stem-out steel tee at the tip of the stem precluded using a chord and rise measurement. (The inside radius, of course, could be measured that way.) A special checking fixture was manufactured with an inside radius to match the specifications. The stem-out tee could then be set against the checking fixture to verify the dimensions. This fixture in fact mimicked the application of the curved tees: they are to be welded to the inside radius of curved plate. If the tees did not match up to the plate, the welders would have serious problems.
Other measures were taken to ensure accuracy and consistency. Special arrangements were made with the steel supplier to improve consistency in the height of the beams. The beams were checked before they were split into tees for any variation in height.
Great care was taken to guarantee that the beams were split right down the center.
And then the rolling was done to the precise specifications and checked on the fixture.
Inspectors from the equipment manufacturer who will use these tees checked the first four rolled tees and approved proceeding with production. As production proceeded, continuous checking was done to guarantee the required quality.
One of the structural steel shapes is the tee. Tees can be supplied straight or curved. The smaller sizes are produced in steel mills; the larger sizes are produced by splitting beams longitudinally.
A customer who is seeking steel tees for use in machinery and equipment or for use in construction would typically contact either a steel mill (if the quantity was sufficient, e.g. a truckload) or a steel service center which would stock structural shapes and sell in smaller quantities (e.g. as few as one piece.)
Some steel service centers have equipment to split tees. Rotary shears, which work something like a can opener, split a beam into two tees. The beams are typically split in the middle of the web, but also can be cut with unequal stems. (What is left of the web is called the “stem.”) When the material is too thick for a rotary shear (above, say, about 7/16in), a cutting torch is used to split the tees.
With either method, when the beam is split residual stresses are released, and the resulting tees relax into a shape curved in one or two planes. The tees look like bananas and need to be straightened.
There are primarily two ways to straighten the tees: ramming and rolling. In the former case, a hydraulically powered ram pushes on the tee when the tee is held at two ends. By repeatedly applying pressure along the length of the curved tee, it can be straightened.
A quicker and more effective way to straighten tees is with a three-roll section bender (also called a “profile bender,” or an “angle roll.”). The curved steel tee is run through large rollers with smaller calibrating rollers until it is straight. The process is faster than ram straightening and provides superior quality. Mill tolerance for straightness of tees is 1/8in variation from straightness in ten feet. Ram bending can achieve this tolerance. With roll straightening, however, tolerances of 1/8in over 40 feet and longer can be achieved.
Most steel service centers do not operate section rollers and so it is common for them to send out tees to be split and straightened by companies who specialize in curving steel. Such companies also curve tees to a specified radius for customers. In some cases the “banana” tees can be fed into a section bender without previously being straightened. The tees can be rolled stem in, stem out, and stem up depending on the application. And tees as large as 18in can be curved these ways.
Steel tees up to 22 x 142-1/2 can be curved stem in, stem out or stem up. At times, however, either the stem is too large or the radius is too tight to roll a tee. One solution is to fabricate a built-up tee.
For example, a customer wanted two tees with a 14in stem ½ in thick and with a 10in wide flange rolled to a 6ft 11in inside radius stem out. Too tight to roll, this size tee to this radius could be made in two pieces.
Two pieces are burned out of 1/2in plate 13-1/2in wide cut to a 16ft 11-5/8in inside radius with 8ft of good arc measured to the outside. The other piece is a 5/8 x 10 flat rolled the easy way to a 6ft 11in inside radius. This piece is then cut in half. The resultant pieces are tacked together to make two tees.
The end use is for lintels at a high-end housing project.
One steel section that does not typically come as a profile from a steel mill is the tee section. Except for small sections, steel tees are produced by splitting beams. A rotary shear or a torch cuts the web of the beam to produce two tees. The cut is usually down the middle of the beam but sometimes is done off center.
When the residual stresses of the beam are released by cutting it, the tees take the shape of a banana. If straight beams are required, then a straightening operation must be done. One method is to press the beams in a cambering machine which restrains the steel section while being pressed with one or two hydraulic cylinders. Another method is to roll the beam sections on an angle roll (also called a section bender or profile bender). The latter method tends to produce a straighter tee.
21in tees up to 80ft long with up to 1in web thickness can be produced. The standard tolerance for tees is 1/8in over 5ft; with the right angle roll, the tolerance can be as precise as 1/8in over any length of tee. Tees 30ft long can be rolled to within 1/16in overall.
After beams have been split into tees, the tees can be curved with the stem in, the stem out, or the stem up, to both large and very tight radiuses and everything in between. And again, to very precise dimensions.
Several steel mills produce small structural steel tees in sizes from ¾” to 2-1/2” which can be purchased at many steel warehouses. Tees can be rolled stem-in, stem-out or stem-up. Larger size tees are made by splitting a structural beam, either by flame cutting or by rotary shear. (A machine that looks like an oversized can opener and works similarly).
Beams up to 80ft long, with a web thickness up to 1in can be split into tees with stems as long as 22in. When beams are split they tend to assume a curved shape with the stems curving out. (They look like bananas.) Depending on the needs of the customer, the resultant tees can either be straightened or curved to a specified radius and often to tolerances closer than standard mill tolerances.
Curving these steel sections can be challenging, e.g. the stem of a steel tee rolled stem-in can ripple or wave if not properly supported. With the right man, machine and method even very tight radiuses can be achieved without any distortion no matter how the steel section is curved.
Tees are used in a variety of applications and industries, e.g. as tank stiffeners, fan housings, and support ribs for machinery. Stainless steel tees are used in food processing and chemical treatment equipment. Aluminum tees are used in architecture including canopies. The applications for larger sections include agricultural and construction equipment as well as roof supports in gymnasiums.
Whatever size required, curved steel tee applications can be found most everywhere.
(Can a woodchuck chuck wood?)
While attending various trade shows either for OEM products like storage tanks, antennas, agricultural and construction equipment, etc., I regularly see where the use of a curved steel section—produced by beam bending, bar bending, angle bending, channel bending or any other section bending—could have reduced the cost of the equipment.
- For example, I have seen a bar rolled the easy way (like a belt) welded to a steel bar rolled the hard way (like a washer) to form a curved angle segment. This time-consuming and expensive part could have easily been produced by a simple curved structural angle.
- We have worked with manufacturers of front end loaders on the redesign of the tubing assembly which holds the bucket on a front-end loader. Curved 5 x 2 x ¼ tubes replace an 11 piece weldment of straight tubes. The new configuration saved money, provided greater visibility to the driver, and improved aesthetics.
- Recently, an engineer from a national laboratory worked with us to design back-up curved tubes to support a dish for an antenna on top of a mountain in Namibia, Africa. The current design called for straight struts to support the curved dish. Expensive welding procedures to be done by certified welders were required on site for the fabrication of the antenna. And the amount of welding was considerable. The new design with curved beams allows for shop fabrication and bolted assembly on top of the mountain. The prototype curved tube was accepted. The new design also improved the rigidity of the antenna, an important benefit for the application.
Steel section bending may produce parts to improve your equipment and machinery. Have your engineers work with our engineers to effect reduced design time, lowered costs, and improved appearance and functionality for the end user.
Can you use curved steel in your products?
George Wendt, President
Chicago Metal Rolled Products
- Is it structurally sound?
- Is it too expensive? And
- Is it readily available to meet a demanding construction schedule.
Is it structurally sound?
- Writing specifically about steel beam bending, Reidar Bjorhovde addressed this question in the Engineering Journal/Fourth Quarter/2006. “When a shape has been curved successfully, with no buckling or localized cracking, the strains the member will experience under actual service conditions will be much smaller than those associated with the curving operation. Once the curving is done, the member can be expected to perform as intended.”
- Although not definitive, based on the experience of most if not all of the major benders and rollers in the world, there has not been an incident of failure in recent memory as the result of incorporating correctly formed curved steel members.
- The curving process, at least when it is done cold, actually causes the tensile and yield to increase. There may be some reduction in ductility, but except in seismic applications or where there are both temperature variations and live loading, this diminution in ductility is insignificant in the application.
- More research will probably be done regarding tube bending due to the increasingly popular use of HSS sections in construction
Is it too expensive?
- Here, perhaps, the question is whether the structural steel bending contributes more to the overall design than the cost of the steel bending. Whether the curved steel helps form a attractive small canopy for an otherwise prosaic structure or creates the enormous curved roof trusses of a structure like the University of Phoenix Stadium, curved steel can add both beauty and functionality to almost any size project.
- The fact that dozens of Bender/Rollers provide the service of curving steel across North America ensures that pricing will be competitive. Call us for a quick, reliable, consistent quotation or for budgetary pricing.
Is it readily available to meet the most demanding construction schedule?
- It is our experience that even in these economically challenging times, quick turn-around times are still required. Turn-around times range from 1 or 2 days to 1-2 weeks with some companies offering same-day service. Adequate supplies of material at mills and service centers also allow for quick delivery.
What concerns, if any, do you have with using curved steel in your construction projects?
George Wendt, President
Chicago Metal Rolled Products
Recently, I gave the presentation at the Kansas City Regional Steel Fabricators Association biannual meeting. 110 steel fabricators, engineers, architects, detailers, and others attended the breakfast.
I talked about the benefits of involving a specialty subcontractor like Chicago Metal Rolled Products in the design process when curved steel elements are included like rolled HSS and W beams.
During the question-and-answer session, a fabricator asked me if there was any special preparation of curved steel sections that should be done prior to galvanizing to avoid unwanted distortion and warpage.
In other words, when we are bending pipes, bending beams, or doing any other steel bending, is there anything prior to the bending process, during the bending process or subsequent to the bending process that would minimize or eliminate the chances of any problems with galvanized curved steel. One member of the audience suggested that the distortion was unpredictable
- I answered that rolled angle rings made out of, say, 2 x 2 x 3/16 angle are galvanized after rolling with no resulting distortion. We also regularly curve, press-brake-formed 6 x 4 x 3/8 angle segments which are galvanized after rolling with no detrimental effects whatsoever.
- Also, ring segments (more common in construction) are sometimes galvanized prior to the rolling process. Depending on the radius, section size, and bending orientation (e.g. x-x or y-y axis), the galvanizing may rub off in the rolling process and need further attention.
- But generally, from our experience of bending pipes, bending beams, or doing any steel section bending, galvanizing subsequent to rolling does not cause warpage or other distortion. It may be the case that, despite the fact that we produce a significant amount of curved steel that is galvanized without a problem, we may not have encountered curved steel sections that actually do distort when galvanized.
- On the other hand, we regularly bend galvanized sheet and plate into cylinders and cylinder segments with no deterioration of the pre-galvanized material.
Has anyone had experience in galvanizing curved steel sections—either positive or negative?
I welcome comments on these matters since the ability to galvanize steel often provides an attractive solution for the built environment.
George Wendt, President
Chicago Metal Rolled Products