What Is Beam Vibration?

Beam vibration is the amount and direction of movement that a beam exhibits away from the point of applied force or the area of attachment. Vibration factors include the material used for construction, the length of the beam, and the amount of force applied. Structural engineering requires the use of mechanical, electrical, and computerized technology to perform vibration testing on beams. These tests supply engineers with information prior to and after the construction of bridges, buildings, and towers concerning capacity to withstand the stress of normal use, extreme weather, or seismic vibrations.

A steel beam may vibrate or move side to side, up and down, and in a horizontal twisting motion. Structural testing generally includes using machinery that applies a shaking motion to a specific location on the structure. These machines shake the structure at both low and high frequencies. Using the shaker method, structures undergo testing, which introduces one frequency at a time or multiple frequencies simultaneously. Instruments attached to the beam or beams record the amount of vibration that occurs.

Testing the strength and durability of single beam construction can be performed by applying static force somewhere along either a free or a cantilevered beam. Analysis on a free beam involves suspending the beam and applying force on either end or anywhere along the horizontal surface. After removing the applied force the beam returns to its original position, however, the metal continues to vibrate. Engineers measure the amount of beam vibration with instruments known as piezoelectric sensors. Smaller vibrations can be measured using electronic oscilloscopes.

These beam vibration-monitoring tools typically show the amount of movement on a graph. Similar tests are performed on cantilever beams, which are usually attached to a solid structure on one end. In some instances, beam vibration can be reduced by applying a thin film of coating material that can include zinc oxide. Once applied, testers repeat the beam analysis process to determine movement reduction values.

Engineers predict beam vibration levels while designing structures. Design software allows architects to create and modify structures based on predicted overall stability. These values produced by these software applications can be compared predicted to values produced by actual testing on existing beams and structures.