Parametric study and comparison of overturning moment and base shear of tall buildings under earthquake and along-wind loads

Increasing the population of large cities and lack of construction area have increased tall buildings. In the present article, the overturning moment and base shear due to the along-wind and earthquake loads have been compared for tall buildings. The buildings are assumed to be located in Tehran city on the type 2 soil and the structure is regarded as a vertical cantilever beam. The along-wind and earthquake loads are computed using the gust-loading-factor method and the linear spectral approach, respectively. First, an example of 120-m high building is presented and evaluated, and then, the effect of the height and aspect ratio parameters are examined in the ranges 80 and 200-m, and 5 to 10, respectively, for the two square and circular cross-sections. For the primary example, the earthquake overturning moment and base shear were dominated respectively by the first and second vibration modes. For the square and circular sections, the ratio of wind-induced overturning moment to the earthquake effect were 1.1 and 0.81 respectively. For the parametric study, the wind and seismic overturning moments were equal to each other at the specific values of the studied parameters, and the wind effects were dominant for the higher values of these parameters. For instance, for the square cross section, the equal point of overturning moment and base shear were respectively 110m and 175m. Finally, by increasing the height and aspect ratio the wind forces were dominant.