Physical structures: Beams and columns

Michael wants to build a wooden table. He has a board to use for the tabletop. But the board can’t just float in the air. Michael needs to add support — table legs. Now the table stands, but it’s not very sturdy.

It sags when Michael places something on it. To fix this, Michael attaches pieces of wood under the edges of the table, running between the table legs. And he adds another piece under the middle of the tabletop. This way, Michael has created a frame for the tabletop to rest on. Now, the weight of the tabletop and of everything placed on top of it, is distributed across the frame and transmitted down the legs to the floor.

The table doesn’t sag anymore. Just like the table, large physical structures, such as buildings or bridges, also need different supporting elements. These supporting, or structural elements carry the weight of those structures, and transfer forces and loads within them. Let’s take this large parking garage. On top of the building is the ceiling.

The ceiling is heavy, and without proper support, it’s very likely to sag or crack under its own weight. So, the ceiling is supported by long horizontal structural elements that help carry the weight, a bit like the horizontal frame on Michael’s table. In engineering, these horizontal structural elements are called beams. Beams are long in relation to their width and height. Beams carry forces that act on them at an angle of 90 degrees: perpendicularly.

The ceiling and beams are supported by vertical elements, just like the legs supporting the tabletop. In engineering, these vertical structural elements are called columns. Columns are tall in relation to their width. Columns are compressed vertically so the loads and forces acting on them are transmitted along their height. Throughout the parking garage, beams and columns are joined together.

They create a path along which weight and forces from higher levels are transferred to the elements below, all the way down to the ground. That’s why columns on the ground floor must be stronger than those on the highest floors. They need to be able to carry the combined weight of all the levels above! Other things that need to be considered when designing a building or a structure, are the material, size, shape, and even location of beams and columns in the structure. And all these are decided based on how much load and force they need to carry or withstand.

Though things such as the weight and cost of beams and columns also play a role. Columns and beams form a framework that distribute the forces acting on a structure and they transmit these forces down to the ground. Thanks to columns and beams, structures remain stable and sturdy, so that we can cross bridges, park our cars, and play board games safely!