Reliability analysis of wind response of flexibly supported tall structures

Statistics and probabilistic analyses and risk assessments can be very useful decision-making tools when dealing with structural-geotechnical problems. Wind loads, dynamic properties of soil underneath the structure and material characteristics of the structure are important factors that affect the wind action on the structure and consequently the structural wind-induced response. Uncertainties in the estimation of these factors as a result of human error or inherent variability are at the forefront for the use of reliability approaches to evaluate the risk of failure during the service period. In the present study, probabilistic base force analyses for tall structures are performed. The substructure approach in which the soil supporting the foundation is modeled by the foundation compliances as functions of soil shear wave velocity is used to account for the soil-structure interaction efficiently. A three-variable probabilistic approach is used to account for the uncertainties in shear wave velocity of the soil underneath the foundation, the concrete strength and the design wind speed on the calculated response and the base forces. The second moment approximation using Taylor series expansion is used to perform the probabilistic analyses of the base cross-section design and resistant forces of a free-standing tower. The first-order reliability method is used to examine the failure probability and the contribution to the total uncertainty. The results show that the dynamic response of the tower increases as soil shear wave velocity decreases. For the range of soil shear wave velocity encountered in practice, the base forces of the structure may increase by up to 20% as a result of the foundation flexibility. For the limit state considered in this study, it was found that the reliability index decreases by up to 15% and the probability of failure increases by up to one order of magnitude as a result of the soil-structure interaction effect. Copyright (C) 2003 John Wiley Sons, Ltd.