Uses of Wide Flange Beams on U.S. Construction Projects
The most commonly utilized I-beam used in the United States is the wide flange beam. The wide flange beam differs from the two other fairly commonly utilized I-beams because it comes complete with flanges that have virtually parallel surfaces.
Wide Flange Beam Grade and Ranges of Yield Strength
A contractor interested in utilizing wide flange beams on a project necessarily needs to become familiarized with both beam grade and ranges of yield strength. At the present time, wide flange beams most commonly are available in grade ASTM A992. This grade has essentially replaced the older ASTM grades used to classify wide flange beams, which were A572 and A36.
Taking into account all possible grades of wide flange beams, the ranges of yield strength available today are:
A36: 36,000 psi (250 MPa)
A572: 42,000–60,000 psi (290–410 MPa), with 50,000 psi (340 MPa)
A588: Similar to A572
A992: 50,000–65,000 psi (340–450 MPa)
Because of its wide usage, A572 remains the most common type of wide flange beam found in buildings today. However, and as was noted, the A992 derivation is taking the place of nearly all options utilized today.
History of the Wide Flange Beam
The method of producing a wide flange beam, and any type of I-beam, depended upon the process of rolling the beam from a single piece of steel. This process was patented in France, in 1849, by a many named Alphonse Halbou, associated with a French company called Forges de la Providence.
In time, the process developed in France was put into use by Bethlehem Steel in the United States. By the mid-20th century, Bethlehem Steel had become the leading supplier of rolled structural steel of different types, including wide flange beams, in the United States. These beams were integral parts of major skyscraper and bridge projects in the country.
Benefits of a Wide Flange Beam
There are a number of benefits associated with a wide flange beam. Chief among them is the fact that these beams are produced to be equal or nearly equal in width and depth. This reality renders the wide flange beam far better oriented vertically to carry an axial load in a construction project. For example, this makes a wide flange beam better suited to use in in multi-story construction projects.
Common Composition of a Wide Flange Beam
In the United States, and most other nations in which the wide flange beam is in use, the beam typically is constructed from rolled steel. To a lesser degree, wide flange beams are produced using aluminum.
In more recent times, wide flange beams are being made from other substances, although on a limited basis and usually for certain residential construction projects. Alternative substances from which wide flange beams are being made include wood containing fiberboard as well as laminated veneer lumber.
Noting that other substances are being used to create wide flange beams, it is important to note that steel wide flange beams remain the industry standard. This is in part due to the strong nature of steel beams, which obviously is crucial in construction projects. In addition, there is significant concern about the potential for rapid loss of strength of wood-based alternatives in the event of a fire. Rolled steel alternatives are much better equipped to maintain their integrity during a fire.
Design Criteria and Wide Flange Beams
Wide flange beams, and other types of I-beams, can be used in construction on their own or with some other material. More often than not, the other material paired up with wide flange beams on a construction project is concrete.
When it comes to the design of any type of I-beam, including a wide flange derivation, certain criteria is taken into consideration. This criteria includes deflection. Deflection represents the stiffness of the beam itself, to minimize deformation.
Vibration represents another consideration. Vibration involves a consideration of the stiffness and mass. This analysis is important in order to prevent unacceptable vibrations. This is particularly necessary in settings that are more sensitive to vibrations, including offices, schools, and libraries.
Another component in the set of design criteria is a consideration of potential shear failure. Shear failure occurs when the web itself fails, the web being the support structure that includes I-beams. Slender web networks can fail by buckling or rippling. This is called tension field action. It is important to note that shear failure is resisted in part due to the flanges contained on the wide flange beam, and on other types of I-beams.
Jessica Kane is a writer for OSHA Campus Online, where you can complete a variety of OSHA training courses 100% online at your convenience.