Comparing Behavior of Structures with mass irregularity under Wind and Seismic Loads

According to Iranian code, Structure components should be designed for the forces caused by wind or seismic load, whichever is greater. Increase in the height to size ratio of a structure causes the impact of the wind load fluctuations on the structure takes on further significance. Additionally, mass irregularity in height results dynamic properties to abrupt changes. In these conditions, wind forces which are estimated using static and dynamic analyses, may don’t sufficient accuracy. In this research, lateral forces of wind are determined using static and dynamic analyses; time history and the forces caused by earthquake are determined by static analysis. These analyses were carried out on 10 and 15-stories regular and irregular (mass irregularity) structures. The lateral forces caused by wind and seismic loads were compared together and the results are presented as comparing shears of stories and relative drift of stories. The studies show that static and dynamic analyses according to Iranian code are not accurate and they show forces and drifts much less than the results obtained from time history analysis. On the other hand, forces obtained from time history analysis in 15-story structures exceeds forces caused by earthquake.

Keywords:

mass irregularity , wind load , seismic load , time history analysis