Structures are often exposed to high-energy vibration sources that can have disastrous consequences. Many industries are emphasizing lighter structures that use less material and cost less too, however this has a downside; lightweight structures have inherently lower damping characteristics and resonances can cause extremely high amplitude vibration. Well thought out structural designs can help prevent resonance and excitation of the structure, thereby minimizing the chances of failure.
Environmental sources of vibration can impact larger structures such as buildings and bridges; examples include: vibration from movement of vehicles, wind currents, earthquakes, ocean currents, etc. These forms of vibration can be difficult to predict and can be random but it is important to be aware of them, especially when designing structures that can lead to loss of human life if they fail. Other vibration sources can be caused by machine components; they include the rotating speed of a machine, imbalances, shocks and impacts. Some of these sources are periodic and predictable while some of them are random in nature.
Several characteristics of a structure will impact how it responds to excitation forces, including its mass, geometry, materials, stiffness and damping, and the location of an exciting force will also modify how it reacts. Therefore, determining or predicting the response to excitation forces is an important step in helping designers create stable structures that are not likely to fail.