Beams and columns are two important types of structural elements that play a key role in creating a safe load path to transfer the weight and forces on a structure to the foundations and into the ground. Beams and columns could be built using the same shapes and materials but each serves a different function and is designed differently.
Beams are usually horizontal structural elements that carry loads perpendicular to their longitudinal direction. Think of a balancing beam in gymnastics. It’s a rectangular object 15 feet long and supported at both ends. When a person is walking on the beam near the middle of the span, their weight is a vertical downward force acting perpendicular to the longitudinal direction of the beam.
Beams are used to support the weight of floors, ceilings and roofs of a building and to transfer the load to a vertical load bearing element of the structure. Sometimes bigger and heavier beams called transfer beams are used to support the cumulative weight of stacked walls or other beams and transfer the load to the supports.
The design or sizing of beams requires understanding of basic physics principles and engineering statics. A structural engineer is trained and fully equipped to check the loads acting on a beam, calculate the forces and stresses on it and choose the material, size and shape accordingly. Part of the engineering consulting work I provide to my clients is structural design of beams in new buildings and restoration or strengthening of existing beams in a structure.
In the case of a new building, there is more flexibility in choosing the size and type of materials for beams that work best for the structure. The most common types of materials I recommend for my clients are beams made out of steel sections, reinforced concrete, grouted masonry, and beams made from wood. All materials have their pros and cons, but are usually selected based on their cost, size and fire rating.
When working on the structural design of a new beam or restoration of an existing one, there are a few factors I take into account. These factors include how much load is acting on the beam, the length or span of the beam, clear height available below the beam or any limitations on geometry, deflection limits of the beam, strength of the material, as well as fire rating and resistance. Similar factors are used when designing columns.
Columns are vertical structural elements where the load is transferred parallel to the longitudinal axis as compression, and sometimes as tension . For example, think of a rectangular table with four legs at the corners. The weight of the table and all the objects on the table is transferred to the floor through the legs acting in compression. In this case the legs can be considered as columns.
Columns are used to support floor/roof beams and the columns of the floor above. The columns at the bottom floor of a tall building must carry the accumulative weight of all the floors above. This is why the location of columns ideally should be consistent throughout all floors. This is not always possible especially with a challenging architectural design where each floor has a different layout. In such cases I often encourage clients to engage the structural design team early in the project to collaborate with the architects to brainstorm the most ideal column layout.
When designing a column in a new building I take a few factors into consideration. I start with calculating the weight of floors/roof supported by the column then choose the material and size as required. The height of the column plays a major part in the overall size of the column. A column that supports 1000 pounds and is 10 feet tall may need to be twice as large as a column supporting 1000 pounds and is 20 feet tall. It all depends on the columns geometry and material properties.
Hopefully this gives you a good idea as to what beams and columns are in a structure and building, and why they are very important structural elements that cannot be overlooked. Next time you walk into a building or drive over a bridge, try taking a look around and figure out which elements you see are used as beams and which are columns. If you are stuck or have any questions with regards to the structure you are looking at, feel free to leave a comment below and we would be happy to help you out!
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