Evaluation of wind loads on buildings using genetic programming

Abstract

Wind loading on low building has been an area of active investigation due to increasing public concern towards severe damage caused by windstorms in recent years. Design wind loading is mainly obtained from different codes, wherein the major source of information on which specifications are based is wind tunnel testing of scaled rigid models under simulated flow. The study reported in this thesis is an effort to examine the efficiency of Genetic Programming (GP) to predict the wind induced pressures on the basis of the data obtained from the wind tunnel testing done by Kwatra et al. (2002). Any Tall building can vibrate in both the directions of Along wind and Across wind caused by the flow of wind. Modern Tall buildings designed to satisfy lateral drift requirements, still may oscillate excessively during wind storm. These oscillations can cause some threats to the Tall building as buildings with more and more height becomes more vulnerable to oscillate at high speed winds. Sometimes these oscillations may even cause discomfort to the occupants even if it is not in a threatening position for the structural damage. So an accurate assessment of building motion is an essential prerequisite for serviceability. Therefore, Genetic Programming has been used for the estimation of the Gust Factor and Base Moment for tall buildings in the along wind direction for Long After Body and Short After Body. In the first phase of the study, the data obtained from the experimental study carried out by Kwatra et al. (2002) is used to develop the database for the gable roof building. The angle of wind incidence, roof slope and pressure coefficient for various zones has been used as the parameters for the development of the equations for the estimation of wind induced pressure on gable roof building. The pressure coefficients thus obtained are compared with the experimental values. Also, equations have been developed for all azimuths for various zones and compared with the experimental values. The wind induced pressure coefficients obtained from Genetic Programming are also compared with the codal values as mentioned in IS875-1987, Part-3. In the second phase of the study, Genetic Programming has been used for the estimation of Gust Factor and Base Moment on tall buildings for the along wind orientation. The database has been developed using the analytical approach as given by A.G. Davenport mentioned in IS875-1987, Part-3. The building height, plan dimensions, design wind speed, gust factor and base moment have been used as the parameters for the development of the equations. The Gust Factor and Base Moment thus obtained from Genetic Programming have been thus compared with the analytical values. The results for the Gable Roof Building and Tall Building are presented in the form of various plots and tables showing the comparison made in the study.