Every pound counts in architectural design. The more materials used, the more expensive the building. However, too little material results in a weak edifice. In structural steel construction, the happy medium comes in the form of the common I beam. Steel-boned bridges, high rises and everything in between make heavy use of I beams for good reason. With structural steel’s mighty strength-to-weight ratio, and with the physics of compressive and tensile forces at play in the design, it’s no wonder the humble I beam comes in so handy.
What Is an I Beam?An I beam, when looked at in cross section, has the shape of the capital letter I. It’s formed with a tall vertical plate and shorter horizontal plates on top and bottom. The vertical plane is called the web, while the horizontal planes are called the flanges. Usually, steel makers produce I beams using the hot rolled method for maximum strength. However, the “I” configuration can also be achieved through the welding together of other steel shapes by a fabricator if needed. Most commonly, builders use I beams for the floor joists and truss systems in steel-framed projects. While they can also serve as columns, other beams with thicker, longer flanges and thicker webs — H beams — often work better for the vertical loads. The I beam configuration offers so much strength, they function best for long, unsupported horizontal spans and cantilevered architectural elements.
So Much Strength for So Little MetalSeparately, flanges and webs have very little strength in construction design. Flanges would bow under vertical loads and webs would bend with horizontal, or shear, stress. But when combined, each cures the other’s strength defects in terms of a beam. Now, a solid bar of steel also would resist forces acting upon it from either direction, but it contains far more material than necessary to do the same job and hold the same weight. You only need a slender central vertical support to take the compression of the load above without bowing; and you only need the flanges to hold the web straight along its length. All that heavy steel between the flanges does nothing but add extra weight — and cost — to the structure. Carve it out, and you have the most strength possible with the least amount of material. What’s not to love about that? You get the same load bearing capacity for a fraction of the weight. Additionally, the gaps between the flanges provide a natural recess into which wiring, piping and other utility lines can run.
Versatility for Any Structural Steel Construction JobWith the well-established physical properties of an I beam, most architectural plans include them, regardless of the simplicity or complexity of the design. Even if the rest of the structure will be framed out in wood, many architects and builders will choose a central I beam support of structural steel. I beams offer the advantage of calming floor vibrations, along with its other features. Construction projects that benefit from liberal use of I beams are:
- retail stores
- agricultural facilities, such as barns, equipment sheds and processing plants
- railroad trestles
- metal-framed houses
- sporting arenas
- entertainment halls
- office buildings
- parking garages
- apartment buildings