NONLINEAR DYNAMIC ANALYSIS OF TALL BUILDINGS UNDER WIND LOADS

Abstract

In this research, the structural systems normally used in tall buildings are presented. The linear and nonlinear finite element analysis of tall buildings under wind loads is carried out. The main purpose was to study the importance of nonlinear dynamic analysis by comparison with nonlinear static analysis based on displacement and shear force results. A selected tall building of reinforced concrete skeleton of 20 stories was modeled and linearly analyzed using the finite element structural analysis program (ETABS). The accuracy of the model was checked by increasing the number of nodes in the corner columns twice. These show monotonic convergence of the results thus confirming the accuracy of the model. Dead load, live load and wind loads were applied to the selected building in accordance to ASCE7-05. The building model was then analyzed using ETABS nonlinear static mode for two load combinations. These results were checked by comparison with published results .The load combination that gave higher results in the static analysis was then used in the nonlinear dynamic analysis of the building. The results obtained from the dynamic analysis were compared with the p delta plus large displacements (P-Δ-W) static results. The comparison of the lateral displacements and story shear show a clear difference between the dynamic and static analysis results. The dynamic results for displacements were higher than static by about 22-28% while the dynamic results for maximum shear was less than the static by about 28%. This confirms the importance of carrying out nonlinear dynamic analysis