Dynamic and Effective Wind-Induced Loads

Rigid structures are structures for which wind‐induced forces of inertia are negligible. Flexible structures are structures for which the wind‐induced forces of inertia are significant. This chapter presents the basic theory that governs the multi‐degree‐of‐freedom behavior of structural systems assumed to be linearly elastic. It discusses the simple case of the linear single‐degree‐of‐freedom system and considers the multi‐degree‐of‐freedom system. The solution of the structure's equations of motion yields the forces of inertia induced by the wind loading, as well as the structure's displacements and accelerations. The chapter reviews, for any specified direction of the wind speed, the determination of the corresponding effective wind loads, defined as the sum of the aerodynamic and inertial loads. In general, the dynamic response to wind of flexible buildings with linearly elastic behavior entails translational motions (sway) along their principal axes and torsional motions about the building's elastic center.