HSS Straight Curved Connections

Hollow structural steel (HSS) is becoming more and more common in structural designs. According to AISC, HSS now accounts for about 18 percent of the structural steel market. HSS has become more popular recently because of aesthetics and its superior resistance to lateral torsional buckling. In terms of curved HSS, we see it being used for AESS (architecturally exposed structural steel) and trusses. Continue reading HSS Straight Curved Connections

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Hot and Cold Steel Bending for a Fountain Sculpture

Each spring my wife and I take a short vacation in California. While there we usually spend a few days on the campus of Stanford University. While walking the campus grounds this spring, a sculpture/fountain caught my eye. We had walked this way many times in past years, but I had not seen this fountain before. It could be that it is a new fountain, or it could be that I had just not noticed it, since it is a fountain, and most of the fountains had been shut down due to the drought in California the last 3 years. With a rain filled winter season, the drought in California has come to an end, and the campus fountains, silent for the last few years have come to life.

This fountain sculpture is simple, yet powerful. The “Cardinal” color and the simple form is eye catching. Employed by a bender/roller, a company that specializes in curving and/or bending structural metal shapes, the fact that this fountain sculpture was designed with curved material had a special interest. In doing some online research I found that the fountain is officially called the Shumway Fountain, but is known to most as the “Red Hoop Fountain”.

Red Hoop Fountain

The Red Hoop Fountain consists of 2 vertical supports, rising about 10 ft above the base of the fountain pool. Each vertical element then has a 90-degree bend, which transitions into the hoop or large horizontal ring. Based on some on-site detective work, I figured the Red Hoop Fountain was made from 12” pipe (12.75 inch outside diameter). The bends from the vertical to the horizontal were either produced by rotary draw bending, or by induction bending. Rotary draw bending is where the material is bent or wrapped around a specific set of dies/tooling. Induction bending is a process where heat, created by an induction coil, is used to heat the metal in a narrow section, which is then bent slowly to a specific radius and immediately cooled (quenched) with water. I would figure these 90-degree bends were done on an induction bender. The horizontal hoop was most likely curved on a section bender. A section bender is usually a 3-roll bending machine that curves/bends the material using pressure, and is done without heating the material. These 3 elements were then welded together to form this simple yet unique fountain sculpture.

The next time you are near Palo Alto, CA, take a few moments to visit the Red Hoop Fountain at Stanford University!

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Steel Cone Fabrication Using Minimum Amount of Pieces

In the past month, I had several customers looking for steel cone fabrication of some larger size cones.

Large or small steel cone fabrication require some design preparation before the actual rolling is performed.  First, the steel plate (or sheet) needs to be cut to a cone “flat pattern”.  The size of that flat pattern will dictate in how many pieces the cone could be rolled.  If the flat pattern is so large it does not fit the available material size or in the plate roller, then the cone will need to be split into 2, 3, 4 or even more pieces. Continue reading Steel Cone Fabrication Using Minimum Amount of Pieces

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Metal Bending Services Questions Answered

We often receive inquiries from customers on the technical aspects of our metal bending services. The most common question is “can you bend this?” and generally the answer is going to be positive. There are many different machines today that assist in bending or rolling everything from thin sheet metal and flat bars to large beams and tubes. If you apply enough pressure, and perhaps a little heat, most metals will bend relatively easily. However, there are many variables that can affect the quality of a bend. It is important to consider the end use to determine what method of bending and rolling will meet the desired result.

Continue reading Metal Bending Services Questions Answered

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Beam Tolerance After Rolling

Curved beams are used everywhere – in structures for functionality or aesthetic appeal, in circular shell stiffening rings on vessels and for monorails or roof trusses. Beams can be curved vertically (the weak-axis) or horizontally (the strong axis). When curving beams, it is important to consider distortion.

Distortion is any deviation from the original cross-sectional shape that usually occurs in every bent member to some degree. Think about curving a straight piece – the curving process is distorting the original shape to a curved shape. The potential for distortion is dependent on several factors, including the bend radius, the thickness of the material, the dimensions of the beam, bending axis, bending method and initial material geometry imperfections from the mill.

When a steel beam goes through the bending process, it is strained past its yield point which usually causes some level of cross-sectional distortion. The procedure creates inelastic compression stresses in the steel that can cause cross-sectional distortion. Distortion is the product of localized contact forces where the rollers of the machine contact the steel beam.

When rolling a beam the hard way or over the strong axis, complete an inspection both before and after rolling to ensure quality. This includes checking that the straight beam applies to AISC mill tolerances. Check the beam to ensure the flanges are perpendicular to the web using a framing square. With the beam flanges sitting on a level floor, check for gaps between the flanges and the floor. Gaps indicate sweep from the mill.

On very critical radius parts, the inside rolling radius must be maintained and fit to a scribe line. The rolling radius tolerance should be specified by the customer (e.g., +/-1/8” from the scribe line). The minimum length tolerance of the rolled section should be measured along the outside radius surfaces using the theoretical outside arc. Rolled sections must allow 4” minimum extra length for fabrication or field trim. The sweep tolerance is usually specified by the customer (e.g., 1/8” on a 36” section). The flange out of square tolerance should also be specified by the customer, (e.g., +1/8/-0”).

Here is a quick overview of tolerance checks on a hard way rolled beam:

  • Radius tolerance (+/-)
  • Minimum length, outside arc (+)
  • Sweep tolerance with 36” template (+/-)
  • Max out-of-square (+1/8)
  • Flange Offset (+/-)
  • Flange Warpage & Tilt (+/-)

 

 

 

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Aluminum Stair Stringers for a Helical Staircase

Early in January 2017, a company from Puerto Rico gave us a call to talk about the aluminum stair stringers for their helical staircase. The company was planning to make a helical staircase for ‘Birth of a New World’, a Christopher Columbus sculpture made by Zurab Konstantines dze Tsereteli. Tsereteli is a famous Georgian-Russian painter, sculptor, and architect known for large-scale and at times controversial monuments like the ‘Tear Drop Memorial’ pictured below, located across from Liberty Statue in New York City.

Tear Drop Memorial
Tear Drop Memorial

The Christopher Columbus ‘Birth of a New World’ statue was originally intended to be a donation to the United States to mark the 500th anniversary of Columbus’s landfall in 1492. After being turned down by several US cities, including Columbus, Boston, Cleveland, Fort Lauderdale, Miami and NYC, the statue was finally offered to Puerto Rico where Columbus arrived in 1493.

Birth of a New World Statue
“Birth of a New World” Statue

After this little history briefing, let’s discuss the details of the aluminum stair stringers used for the staircase leading to the ‘Birth of a New World’ statue. The staircase is in the center of the statue and spirals upwards. The statue itself is located by the ocean. In order to avoid corrosion issues, the customer chose to use a 10-inch aluminum channel made out of 6061 aluminum. This represented a challenge given the characteristics of forming aluminum stair stringers. Following CMRP’s engineering recommendation, the aluminum material thickness was increased to 5/16 help prevent deformation of the flanges.

Another big challenge in this project was the placement of the stair itself.  The circular wall within the statue was only 6-feet in diameter.  Within this space, the customer needed to fit an inside and outside aluminum stair stringer, going up 3 floors, each 13-feet high.  That implied an inside stair stringer with only 2-foot 2-inch internal radius with 52° of pitch.  In addition, outside stair stringer would run only 1-inch away from the concrete wall which required extremely accurate rolling/forming operations.  The job being all the way in Puerto Rico would give us no room for inaccuracies, the aluminum stair stringers had to be perfect.  As you can see from the pictures, they were!

"Birth of a Nation" Staircase
Helical Aluminum Stair Stringer
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Sheet Metal Rolling

Before we disscuss sheet metal rolling, let’s first get a few basics about sheet metal:  what is it; how it’s made; how it’s designated; and how it can be used.

Sheet Metal is a metal being formed by an manufacturing process into thin, flat pieces. The sheet metal rolling process consists of passing metal stock through one or more pairs of rolls to reduce the thickness and to make the thickness uniform.

Sheet Metal Forming Between Rolls
Sheet Metal Forming Between Rolls

To determine the designation of sheet vs. plate in general terms we can say that anything 1/8″ and thicker is a plate and anything less than 1/8″ is a sheet. The thickness of sheet metal is normally designated by a non-linear measure known as gauge. The larger the gauge number, the thinner the metal. Commonly used steel sheet metal ranges from 30 gauge to about 6 gauge.

Sheet Metal Gauges
Sheet Metal Gauges

Sheet metal can be available in flat pieces or coiled strips. It is one of the essential shapes used in metalworking. Innumerable everyday objects are fabricated from sheet metal. Sheet metal can be cut and bent into an unlimited number of applications like: ductwork, machine guards, other machine components, architectural column covers, wall coverings and downspouts, tank bodies, just to name a few.

There are multiple manufacturing process that sheet metal can be formed by: bending, curling, incremental sheet forming, laser cutting, perforating, press brake forming, punching, roll forming, rolling, spinning, stamping, water jet cutting.

As a metal rolling company we have been rolling the Sheet Metal since our conception in the 1908. We specialize in rolling of lock-seam pipe, welded pipe and open-butt-joint pipe out of carbon steel, stainless steel, brass, copper and other alloys including aluminum. We can also roll sheet metal in to other shapes.  Contact Chicago Metal Rolled Products for fast and accurate quotes on rolling sheet metal.

Rolled Sheet Metal Shapes
Rolled Shapes from Sheet Metal
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Metallic Bonding and Distortion in Curved Steel

When describing cross sectional distortion of cold-formed steel members the term fluidity can from time to time be observed. This might rattle most people’s logic, as steel is a well-known solid. It is not that structural steel exists both in solid and liquid state simultaneously during cold forming, but rather that when a stress great enough to yield a member, is applied to that member through a bending moment, steel members display fluid like characteristics in the form of flow. This is commonly seen in wall thinning and thickening and or a reduction in the cross section of a member. To explain how this is possible it is necessary to have a working knowledge of steel and ultimately steel’s base metal, iron (Fe), on the molecular level.

Steel is an alloy or a mixture of Iron and Carbon with other elements working as additives to alter the chemistry and enhance certain properties and or characteristics of the steel.  Iron, steel’s base metal is the most common element on earth. Pure it is relatively soft and not very strong but its interaction with carbon makes it one of today’s most utilized materials. When we speak about the cold forming of steel and how during that process steel displays fluid/flow like characteristics; we must strongly consider steels’ base metal, iron. When Iron starts solidifying from liquid state it does so in crystalline form; meaning that at the molecular level, iron atoms arrange themselves in a lattice type structure. The bonds formed between iron atoms are the key to the fluid/flow like characteristics that steel display when under stress. Metallic bonds unlike covalent or ionic bonds (where two atoms share one electron or one atom takes an electron away from another atom to form a bond) share their valance electron over the entire lattice structure of atoms, known as a delocalization of the valance electron. This is important, as this type of bonding allows for iron to be malleable meaning it can be shaped; it also allows for iron to be ductile meaning it can be stretched and drawn. These fluid/flow like characteristics are types of plastic deformation. The delocalized sea of electrons acts like a bonding blanket encompassing the iron lattice structure, keeping the lattice bonded but allowing the atoms within the lattice structure to move or slip without breaking bonds. This dislocation or slippage of the lattice structure is considered to be a linear defect of the iron crystal. But this defect in the iron crystal is not a bad thing in the sense of the word, but rather is what makes plastic deformation even possible. The ease of movement of these dislocations is what determines the material’s strength and yield. Any obstruction or defect within the lattice structure makes slippage/plastic deformation more difficult; even the slippage of dislocations make plastic deformation more difficult. Dislocation of slip planes create other dislocations that obstruct the movement of dislocations, this is known as work hardening.

Steel comes into play in all of this when you add a percentage of carbon to the iron mixture. As said before pure iron is rather soft, displaying flow/fluid like characteristics in the form of malleability and ductility but ultimately it lacks the strength one would seek in a building/construction material. Add 0.12-2.0% of carbon into the mix and iron becomes the material we know today as steel. As iron and carbon are heated the lattice structure of iron changes and rearranges on itself. These different forms of lattice structures are known as allotropes. The allotropy of iron is extremely important as these allotropic formations, when heated to certain temperatures, interact with carbon in different ways. Through substitution, this allows the carbon atom to join the lattice structure. It is this positioning of the carbon atom within the lattice structures that gives steel its strength and toughness. To a certain extent increasing the carbon content within the alloy steel mixture will increase strength and hardness of the material. But in general it is the hardenability of the steel alloy mixture that is increased, as making steel harder is generally achieved through heat treating and cooling times which either allows or prevents the carbon atom to escape or diffuse from the lattice structure. Add too much carbon to the mixture and the material gets harder but less tough as the material cannot absorb energy efficiently and the material becomes brittle and susceptible to cracking. Ultimately, it must be thought that when bending/forming i.e. plastically deforming steel members we are really deforming the slip planes/dislocations of the iron/carbon molecular lattice; and that the carbon atoms placement within the lattice structure prohibits the slippage of the dislocations to a certain degree, making steel harder and stronger than its base metal, iron. Now of course in the steel we know today there are many other elements added into the mixture to assist and enhance certain characteristics like hardness, toughness, stiffness, etc. but carbon is the major alloying element that makes iron the material we know today as steel. Many of steels attributes including those that display fluid/flow like characteristics can be attributed to steels base metal iron and its metallic bonds.

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Super Solar Canopies for Super Bowl LI at NRG Stadium

On Sunday, February 5, 2017, also known as Super Bowl Sunday, millions of football fans and others will watch the Atlanta Falcons battle the New England Patriots to see who will be Super Bowl LI Champions. Though most of us will watch this battle on TV, a capacity crowd of 71,795 fans will gather at NRG Stadium in Houston, Texas to watch this game live. Continue reading Super Solar Canopies for Super Bowl LI at NRG Stadium

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Curved Beam Design Procedure

Form plus function almost always results in a great design. Architectural design in addition to engineering design represents each of the variables in the equation for a successful design solution. The architectural aspect of a curved beam design achieves ideal appearance and functionality. A design that has been well engineered produces an efficient and capable performance solution. Continue reading Curved Beam Design Procedure

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