Damping Ratios of Reinforced Concrete Structures Under Actual Ground Motion Excitations
Structural damping ratio which quantifies the energy dissipation of civil structures under external excitations plays a critical role in the seismic design and assessment of civil structures. In existing building design provisions and guidelines, however,
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Damping Ratios of Reinforced Concrete Structures Under Actual Ground Motion Excitations Dan Lu, Jiayao Meng, Songhan Zhang, Yuanfeng Shi, Kaoshan Dai, and Zhenhua Huang
Abstract Structural damping ratio which quantifies the energy dissipation of civil structures under external excitations plays a critical role in the seismic design and assessment of civil structures. In existing building design provisions and guidelines, however, the structural damping ratio is only suggested either as a single fixed value or as an optional value for the general structure type adopted. For example, damping ratio 5% is commonly recommended for all reinforced concrete (RC) structures in practical seismic design, which may not be sufficient to represent the realistic damping features of different RC structures under ground motions with different amplitudes. This research explored deeper understandings on the structural damping features of different RC structures under actual ground motion excitations. A series of seismic response records of RC structures were collected from the “Center for Engineering Strong Motion Data” (CESMD) database. These records were then categorized into three typical lateral resisting systems: moment-resisting frame systems, shear wall systems, and moment-resisting frame plus shear wall systems. The equivalent structural damping ratios for different systems of RC structures were then estimated based on the categorized response records with different amplitudes. Finally, an empirical statistical relationship was established, offering a refined basis for civil engineers to reasonably choose the equivalent damping ratios during the design and post-earthquake assessment of the RC structures. Keywords Damping ratio · Modal parameter identification · Nonlinear · Strong motion observation · Empirical formulas
36.1 Introduction In recent years, the number of aged buildings suffering from natural disasters has shown an increasing trend. This increasing trend has stimulated a rapid development of the state-of-the-art devices for vibration control. The application of such devices requires the reliable information of structural damping ratio, which is a commonly used physical parameter to characterize the energy dissipation of structural dynamic response. However, the actual structural damping ratio for existing and newdesigned buildings subject to earthquake and wind loading is difficult to be precisely quantified because of its complicated mechanism, which has become a troublesome issue in optimizing structural designs [1]. Unlike characterizing the structural stiffness and mass properties, which can be intuitively evaluated from the material and geometric features, quantifying the structural damping ratio is much more complicated. Currently, the structural damping ratio of civil structures is usually obtained by experimental/field tests, which measure the responses of structures to different excitations [2], such as shake tables, wind loadings, environment loadings, or strong earthquakes [3]. Among these experiments
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