CRITICAL EVALUATION, OF INDIAN STANDARD CODE FOR WIND FORCES ON PITCHED ROOF LOW-RISE BUILDINGS

Abstract

This study presents critical evaluation of the wind pressures on low rise pitched roof buildings and comparison with some of the International wind codes. In particular the changes proposed in the draft Indian code have been examined. A rather large number of factors affect wind -loads on the Low rise pitched roof buildings; not all of which are included in the present IS code. While some of the factor has been considered in the proposed IS code (like wind directionality factor, area reduction factor, combination factor and interference factor), it is felt from this study that some more factor need probably still be added, much as, shielding factor, building importance factor and permeable cladding reduction factor. The study has two distinct aspect that have been covered, i) examining the proposed changes in the draft code and ii) comparing the proposed IS provision with the other International Codes of practice. The correlation of wind pressures over a large structure or its component is better expressed by the area being considered rather than the large dimension involved. Thus for k2 factor has been modified to exclude the structure size effect which is proposed to be accounted by the area reduction factor. A cyclone are factor has further been included in the expression for wind speed, while a combination factor K(, is added for reducing the pressure for design of the structural frame work besides the wind directionality factor Kd. This factor has been compared from different codes to establish their rationality. Finally the significance of the various factors has been brought out and example of single storey pitched rood building solved to illustrate the differences existing in various International wind codes.