Abstract
The seismic behavior of asymmetric structures with a flexible diaphragm was studied by conducting inelastic dynamic time‐history analyses. Asymmetric structures with different configurations of mass, stiffness, and strength centers, in combination with a wide range of diaphragm flexibility, were evaluated. The behavior of structures was studied by considering three aspects: (1) effect of structural asymmetry on diaphragms deformation; (2) effect of diaphragm flexibility on demands of the lateral load‐resisting elements; (3) optimum configuration of mass, stiffness, and strength centers to limit important engineering demand parameters in asymmetric structures with a flexible diaphragm. The results showed that the shear‐dominant deformation of diaphragms is sensitive to both structure asymmetry specifications and the degree of diaphragm flexibility; therefore, it can be used for the qualitative classification of the seismic behavior of structures. Also, the center of strength in structures with flexible diaphragm is more important relative to the stiffness center and has a significant effect on engineering demands at all levels of diaphragm flexibility. Moreover, it was found that a suitable configuration of centers in torsionally stiff structures depends on the degree of diaphragm flexibility, in addition to the intensity of earthquakes (structure yield level) and selected engineering demand parameter.
Highlights
In some structures, the assumption of a fully rigid seismic diaphragm is far from reality and can lead to a significant difference in the actual responses of structure and the results of analysis [1,2,3]
The degree of diaphragm flexibility and distribution of structure stiffness and strength are key parameters that affect the distribution of forces between the lateral load-resisting elements (LLREs) simultaneously
The results indicated that diaphragm flexibility is more important in structures with stiffer LLREs such as shear walls [2, 12], lower story height [12], less number of stories [1, 12,13,14], less number of structure spans [1, 13], and larger aspect ratios [12,13,14]
Summary
The assumption of a fully rigid seismic diaphragm is far from reality and can lead to a significant difference in the actual responses of structure and the results of analysis [1,2,3]. The type of floor system is an important factor in the degree of diaphragm flexibility. Diaphragm flexibility depends on the floor type, and on other parameters such as the diaphragm aspect ratio and ratio of diaphragm stiffness to adjoining lateral elements stiffness [6]. Previous studies suggest that plan-asymmetric structures have more potential for diaphragm flexibility [2, 8, 9]. The degree of diaphragm flexibility and distribution of structure stiffness and strength are key parameters that affect the distribution of forces between the lateral load-resisting elements (LLREs) simultaneously. When the diaphragm is quite rigid, the distribution of stiffness and strength in the structure plan has the greatest effects on the seismic response of plan-asymmetric structures. For absolutely flexible diaphragms, the distribution of force between the LLREs is only based on their tributary area
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