Effect of wind on structure. Structural Engineers（风对结构的影响。）.pdfVIP

Effect of wind on structure. By Sukanta Adhikari Wind produces three different types of effects on structure :static,dynamic and aerodynamic.The response of load depends on type of structure.When the structure deflects in response to wind load then the dynamic and aerodynamic effects should be analysed in addition to static effect.Sound knowledge of fluid and structural mechanics helps in understanding of details of interaction between wind flow and civil engineering structures or buildings Flexible slender structures and structural elements are subjected to wind induced along and across the direction of wind. When considering the response of a tall building to wind gusts, both along-wind and across-wind responses must be considered. These arise from different the former being primarily due to buffeting effects caused by turbulence; the latter being primarily due to alternate-side vortex shedding. The cross-wind response may be of particular importance because it is likely to exceed along-wind accelerations if the building is slender about both axes. Any building or structure which does not satisfy either of the above two criteria shall be examined for dynamic effects of wind.: a) Buildings and closed structures with a height to minimum lateral dimension ratio of more than about 5.0. and b) Buildings and closed structures whose natural frequency in the first mode is less than 1 Hz. Wind induced oscillation There are three forms of wind induced motion as follows:- a) Galloping - Galloping is transverse oscillations of some structures due to the development of aerodynamic forces which are in phase with the motion. It is characterized by the progressively increasing amplitude of transverse vibration with increase of wind speed. Non circular cross section are more susceptible to this t