Some Remarks on Experimental Estimation of Damping for Seismic Design of Civil Constructions

Rainieri, Carlo; Fabbrocino, Giovanni; Cosenza, Edoardo

doi:10.1155/2010/737452

Cited by 45 publications

(23 citation statements)

References 17 publications

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“…They have been shown to yield good estimates of the natural frequencies and mode shapes under normal operating conditions, but estimates of modal damping ratios are not as reliable (Brownjohn, 2003). This has generally been attributed to imperfect assumptions about the input forces (stationary white noise), leakage, or insufficient averaging in the estimation of spectral density (see section 2.5.3) (Rainieri et al, 2010).…”

Section: Ambient Vibration Testsmentioning

confidence: 99%

“…This agrees with past findings, which indicate that damping estimates are typically prone to large uncertainty. This may be the result of imperfect assumptions about the input forces (that they are stationary, with a flat spectrum across the frequency range of interest), leakage, or insufficient averages in the estimation of spectral density (Brownjohn, 2003), or in this case partial identification of the SDOF bells in certain setups (Rainieri et al, 2010). The accuracy of the experimental mode shape estimates was investigated using the modal assurance criterion (MAC) between the model and EFDD mode shapes.…”

Section: Comparison Of Theoretical and Experimental Modal Parametersmentioning

confidence: 99%

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In Situ Dynamic Characteristics of Reinforced Concrete Shear Wall Buildings

Gilles

McClure

2012

Structures Congress 2012

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Structural engineers routinely need to make assumptions about the dynamic properties (natural periods, mode shapes, and damping) of a building to simulate its response to dynamic loads, such as strong winds or earthquake ground motions. However, the assumed properties may significantly differ from those of the actual building, once it is constructed, due to differences between the idealized model and in situ conditions. The main objectives of this study are to evaluate how common models and assumptions used to predict the dynamic properties of buildings compare to those measured in actual buildings, and to develop improved prediction models.To this end, ambient vibration measurements were performed in 39 buildings on the island of Montréal and the dynamic properties of up to six vibration modes were identified, for each of these buildings, using the enhanced frequency domain decomposition method. Though the initial goal was to obtain a representative sample of different types of buildings, 27 of these 39 buildings turned out to be reinforced concrete buildings with shear walls providing the main resistance to lateral loads. Hence, the scope of this study was narrowed to the dynamic properties of reinforced concrete shear wall (RCSW) buildings. The measured dynamic properties of this subset of 27 buildings were then used to evaluate different models, proposed in building codes and in the literature, to predict the natural periods and damping characteristics of these types of buildings. Finally, simple models to predict the natural periods of torsion and second translation modes were proposed based on regression analyses. These models agree very well with those that have been proposed in the literature. Again, equations corresponding to different probability levels (mean, mean minus one standard deviation, and mean plus one standard deviation) were produced as a measure of uncertainty.This study should help engineers select realistic values of the dynamic properties of RCSW buildings for structural analysis and design, and should ultimately improve engineers' ability to predict the dynamic response of these buildings. Further, the proposed models could lead to improved recommendations in building codes.iii This research could not have been possible without the help of many building owners and managers, who allowed our team to perform vibration measurements in their buildings. I would also like to thank the numerous graduate and undergraduate students who were involved in these tests for both their participation and the stimulating discussions that often ensued:

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Section: Ambient Vibration Testsmentioning

confidence: 99%

Section: Comparison Of Theoretical and Experimental Modal Parametersmentioning

confidence: 99%

In Situ Dynamic Characteristics of Reinforced Concrete Shear Wall Buildings

Gilles

McClure

2012

Structures Congress 2012

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“…This approach uses four main steps in order to estimate the damping ratio, as is illustrated in Figure 8. Rainieri et al [22] have suggested some basic test and data processing rules in order to obtain reliable damping ratio estimations with the EFDD method. Firstly, a total record length equal to 1000-2000 times the first natural structural period is usually recommended.…”

Section: Operational Modal Analysis and Damping Ratio Estimationsmentioning

confidence: 99%

Damping Assessment of Lightweight Timber Floors Under Human Walking Excitations

2019

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Vibrations on timber floors are among the most common serviceability problems in social housing projects. The presence of low damping levels on these floors could cause excessive vibrations in a range of frequency and amplitude that generate discomfort in users. This study focuses on the influence of the damping ratio in the dynamic serviceability of social housing timber floors due to walking excitations. More than 60 human-walking vibration tests were conducted on both laboratory and in-situ timber floors. The floors were instrumented with accelerometers, and fundamental modal damping ratios were estimated by applying Enhanced Frequency Decomposition Domain (EFDD) and Subspace Stochastic Identification (SSI) methods. The vibration dose value (VDV) was used to estimate the dynamic serviceability of floors. The results indicated that timber floors had an impulsive-type vibration response, with fundamental damping ratios between 1.9% and 14.8%, depending on their constructive characteristics. The in-situ floors had damping ratios between two to three times greater than the laboratory floors due to the presence of non-structural elements. Finally, it was possible to demonstrate that the floors with the highest damping ratios reached lower vibration dose values and, therefore, a better dynamic serviceability performance.

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“…As for the damping ratios, the experimental results show no good harmony and distribution. This is because the damping mechanism of large civil structures is complicated; thus the error bounds for damping ratio estimates could be large (see, for instance, [19]). Figure 11 shows the corresponding mode shapes of the four extracted modes.…”

Section: Sd With Confidencementioning

confidence: 99%

“…Although the robustness and effectiveness of SSI for OMA have been extensively demonstrated, it is still worth improving the accuracy of the extracted modal parameters and reducing the computational cost of the algorithm. Rainieri et al [19] proposed a procedure for accurate damping estimation under operational 2 Shock and Vibration conditions by SSI. Their study gave a contribution towards standardization of testing and data processing procedures to make the error bounds of modal damping ratio estimates as low as possible.…”

Section: Introductionmentioning

confidence: 99%

Operational Modal Analysis Based on Subspace Algorithm with an Improved Stabilization Diagram Method

Qin

Kang

Wang

2016

Shock and Vibration

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Subspace-based algorithms for operational modal analysis have been extensively studied in the past decades. In the postprocessing of subspace-based algorithms, the stabilization diagram is often used to determine modal parameters. In this paper, an improved stabilization diagram is proposed for stochastic subspace identification. Specifically, first, a model order selection method based on singular entropy theory is proposed. The singular entropy increment is calculated from nonzero singular values of the output covariance matrix. The corresponding model order can be selected when the variation of singular entropy increment approaches to zero. Then, the stabilization diagram with confidence intervals which is established using the uncertainty of modal parameter is presented. Finally, a simulation example of a four-story structure and a full-scale cable-stayed footbridge application is employed to illustrate the improved stabilization diagram method. The study demonstrates that the model order can be reasonably determined by the proposed method. The stabilization diagram with confidence intervals can effectively remove the spurious modes.

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Some Remarks on Experimental Estimation of Damping for Seismic Design of Civil Constructions

Cited by 45 publications

References 17 publications

In Situ Dynamic Characteristics of Reinforced Concrete Shear Wall Buildings

In Situ Dynamic Characteristics of Reinforced Concrete Shear Wall Buildings

Damping Assessment of Lightweight Timber Floors Under Human Walking Excitations

Operational Modal Analysis Based on Subspace Algorithm with an Improved Stabilization Diagram Method

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