Depending on the nature of the impact on the structure, loads are divided into static and dynamic. Loads are considered static if they change very slowly (with an infinitely small increment in time), without jolts or impacts. Dynamic loads are those that can change their magnitude, direction or position in relatively short periods of time. Dynamic loads are functions of time and are designated P(t), m(t), q(t). All parameters that depend on dynamic loads (e.g. displacement, force, stress) will also be functions of time and are written as M(t), Q(t), Δ(t), σ(t) etc.
Dynamic loads impart acceleration to the masses of a structure, causing inertia forces and vibrations of the structure. Structural dynamics is a section of structural mechanics that studies the principles and methods of calculating structures for dynamic loads. Dynamic calculations are performed to solve two main problems: determining the frequencies of system vibrations and checking it for resonance; determining the greatest (amplitude) values of internal forces and displacements caused by a dynamic load. Here are the most typical types of dynamic loads in a construction practice: (click below on page 2 to continue )
