GUST FACTOR METHOD FOR WIND LOADS ON BUILDINGS AND INDIAN CODAL PROVISIONS

The last century has witnessed remarkable developments in the treatment of wind loading in structural design. During this period the description of wind loading has moved from relatively simple, straight forward, static drag forces to much more sophisticated models, involving all the manifold aspects of climate, meteorology, aerodynamics, dynamics and more recently the reliability. Present Indian Codal Provisions incorporate basic wind speed map based on statistical analysis of peak winds (3 seconds) extreme wind speed data recorded at 43 Meteorological stations spread over the whole country. The code also underlines that the flexible structures should be designed by Peak Wind Approach as well as Mean Wind Approach associated with Gust Factor and severe of the two is to be considered as design load. The hourly wind speeds required in Gust Factor Method have been suggested by converting peak wind speeds referred as basic wind speeds in the code. The present study has been undertaken with the objective of critically examining the Gust Factor Method incorporated in the present Indian Standard for wind loads, IS 875 (Part 3) 1987. For the study 25 storied framed steel building having square shape in all the four terrain categories has been chosen. The wind loads induced at various heights, base shear and base moments for the building has been computed by Peak Wind Approach as well as Mean wind Approach associated with Gust Factor. There are wide variations in the values obtained by two approaches