What Is Beam Buckling?

Many of today’s buildings are constructed using steel beams and other modern materials. This procedure contrasts with the all-wood construction seen in older buildings, such as churches and barns. It is important to note that the term “beam construction” can refer to either wood or steel. Here, however, the term refers to a steel beam, and beam buckling is a distortion in shape that occurs when the load on the beam is greater than the beam is designed to carry.

Steel beams can support much heavier loads than a wooden beam of the same size, making steel an increasingly popular choice in building designs. The amount of weight a particular beam can withstand is known as the beam load. When any beam, wood or steel, is loaded with more weight than it can handle, failure occurs. This failure is known as beam buckling. Thankfully, structural engineering can be used determine the limits of load bearing beams and design a project to prevent any failures.

Engineers use a mathematical formula, or beam equation, to determine how much weight any given beam can withstand. Essentially, this equation helps determine how much weight a beam can hold and how far it can flex or bend before beam buckling occurs. When beams are subjected to a load, there is a limited amount of distortion allowed. Exceeding the allowable amount will cause a beam to buckle or fail.

While wooden beams will simply break, steel beams distort beyond a point where they can flex back into shape, also known as beam buckling. When beams buckle, they lose all structural integrity, possibly leading to structural collapse. For example, steel roofs are designed to hold a certain amount of weight. When severe snowstorms apply more weight than the design can handle, beam buckling occurs. Beams that flex under a load can return to their normal shape when the load is removed, but beams that have buckled will not.

Steel beam structures are often designed with a small safety margin to reduce the risk of failure. For instance, a steel roof has multiple beams supporting it, and if one beam fails, the requirements on the surrounding beams increase appropriately. If this principle had not been applied, the entire structure could fail due to one beam buckling — similar to a house of cards.

Beams are available in many sizes to accommodate different projects, and are chosen based on their rated load. When a structural load is applied to a beam, it will flex or bend slightly until the load is removed. If an excessive load is applied, the beam goes beyond the point of flexing, to buckling, and all integrity is lost. This emphasizes why structural engineering is so important.