1- Arak University
2- Arak University ,p.zakian@modares.ac.ir
2- Arak University ,
Abstract: (109 Views)
Damage of both building and non-building structures (including the space structures) against earthquake is of great importance for civil engineers, because collapse of such large structures may have significant casualties and economic losses. Space structures are classified as large-scale structures and can cover a large space without columns. Seismic behavior of these structures is different from building structures. There are different types of space structures considering the geometrical aspects, which are effective in the damages causing economic and life losses. A space structure has three-dimensional behavior, and their higher-mode effects are remarkable. On the other hand, the weight of these structures is relatively low that may cause an unrealistic reduction in the calculation of seismic force in a static analysis. Therefore, the static analysis cannot capture their structural response effectively. Traditionally, the dynamic analysis is utilized for seismic design of space structures due to their complex structural behavior. Thus, in this paper, seismic design of two single-layer domes is performed using two dynamic analyses: time history analysis and response spectrum analysis. Although there are some studies on seismic design of domes, further investigations are required due to the structural diversity of different domes and the difference in their seismic behavior. Here, the ribbed and Schwedler domes under gravity and seismic loads are analyzed dynamically. The parameters of the design response spectral acceleration are based on ASCE7-16, and the site class (based on the soil type) is selected as “D”. Both horizontal and vertical components of seismic excitations are utilized in the dynamic analyses, because all these components are effective in design of a dome structure. The damping ratio is assumed to be 2% in the dynamic analyses based on the relevant literature. In the response spectrum analysis, the vertical seismic load is expressed in terms of dead loads in the response spectrum analysis. In the time history analysis, seven ground motion records are selected based on the seismic zone. These ground motion records are scaled using both amplitude scaling and spectral matching approaches. The vertical components are scaled to the specific vertical design spectrum obtained from ASCE7-16. In this study, seismic design of the ribbed and Schwedler domes with a span of 36 meters and a height of 6 meters are carried out with some limitations on the member stress ratios and top nodal displacements. The structural designs based on the time history analysis and the response spectrum analysis are compared. The same cross-sectional areas are used in designs of the dome structures to compare the effects of these dynamic analysis methods better. In general, the top node displacement and stress ratios of the dome obtained using time history analysis is larger than that obtained using spectral dynamic analysis. Accordingly, the results indicate that the structure designed with the time history analysis is heavier than the structure designed with the response spectrum analysis. Obviously, although the time history analysis provides a better understanding of the dynamic behavior of the structure, it requires much higher computational cost than the response spectrum analysis.
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