scholarly journals IDENTIFICATION OF ROTATIONAL INPUT MOTION AND DAMPING RATIO USING HORIZONTAL ACCELERATION RECORDS

2020 ◽  
Vol 85 (767) ◽  
pp. 51-60 ◽  
Author(s):  
Takuya SUZUKI ◽  
Takaki TOJO
Keyword(s):  
Damping Ratio ◽  
Horizontal Acceleration ◽  
Input Motion

A Damping Modification Factor for Horizontal Acceleration Spectrum from Subduction Slab Earthquakes in Japan Accounting for Site Conditions

2020 ◽  
Vol 110 (4) ◽  
pp. 1942-1959
Author(s):  
John X. Zhao ◽  
Mingxiu Jiang ◽  
Xiaonan Zhang ◽  
Lili Kang
Keyword(s):  
Damping Ratio ◽  
Site Effect ◽  
Site Conditions ◽  
Design Spectrum ◽  
Horizontal Acceleration ◽  
Displacement Spectra ◽  
Modification Factor ◽  
Standard Deviations ◽  
Source And Path Effects ◽  
Site Classes

ABSTRACT We present a damping modification factor (DMF) model for the total acceleration spectrum from subduction slab earthquakes. The model can be used for scaling a 5% damped design spectrum not associated with a particular earthquake that occurred in a subduction slab. The DMF model uses site-period-based site classes as the site-effect proxy. DMF models were constructed based on the spectrum for 13 damping ratios and 34 spectral periods; the DMF values can be calculated for any damping ratio between 1% and 30% and at any spectral period between 0.03 and 5.0 s. At moderately long and long spectral periods, the DMF values for acceleration spectrum are similar to or less than those for the displacement spectrum for a damping ratio of less than 5%, whereas the DMF values for the acceleration spectrum are similar to or larger than those for the displacement spectrum when the damping ratio is more than 5%. The standard deviations for acceleration and displacement spectra are similar at short or moderately short spectral periods, but those for the acceleration spectrum are about twice those for the displacement spectrum at long spectral periods. All standard deviations decrease linearly with increasing damping ratios in the logarithm scale when the damping ratio is less than 5% and increase linearly with increasing damping ratios in a logarithm scale for the other damping ratios. A set of simple functions for calculating various standard deviations is presented. The spectra from the Zhao, Jiang, et al. (2016) study for slab events scaled by the DMF values for other damping ratios vary smoothly with spectral period and have a trough at short spectral periods for a large event, a short distance, and high damping ratios. The relatively large between-event and within-site standard deviations are from the source and path effects.

Time-Variant Modal Parameters and Response Behavior of a Base-Isolated Building Tested on a Shake Table

2018 ◽  
Vol 34 (1) ◽  
pp. 121-143 ◽  
Author(s):  
Rodrigo Astroza ◽  
Gonzalo Gutiérrez ◽  
Christian Repenning ◽  
Francisco Hernández
Keyword(s):  
Damping Ratio ◽  
Nonlinear Behavior ◽  
Modal Parameters ◽  
Shake Table ◽  
Isolation System ◽  
Equivalent Damping ◽  
Stochastic Subspace Identification ◽  
Modal Properties ◽  
Highly Correlated ◽  
Input Motion

This paper presents the identification of the instantaneous modal properties and the experimental response of a full-scale, five-story base-isolated RC building tested on a shake table. A suite of earthquake motions of various intensities was applied to the building to progressively increase the seismic demand. The deterministic-stochastic subspace identification method is employed to estimate the variations of the modal properties of the building by employing a short-time windowing approach. The changes of the modal parameters during the seismic motions are tracked and analyzed. Observed and measured responses of the structure are analyzed and correlated with the variation of the identified modal parameters. The nonlinear behavior of the isolators generates the variation of the identified natural frequencies and equivalent damping ratios of the building, which change in agreement with the input motion intensity. A high correlation between the effective stiffness of the isolators and the instantaneous frequency of the first mode is found. The effective damping ratio of the isolation system and the instantaneous damping ratio of the fundamental mode of the building are highly correlated.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

Influence of repeated freeze-thaw on dynamic modulus and damping ratio properties of silty sand

2013 ◽  
Vol 5 (5) ◽  
pp. 572 ◽  
Author(s):  
Wang TianLiang ◽  
Ma Chao ◽  
Yan Han ◽  
Liu JianKun
Keyword(s):  
Dynamic Modulus ◽  
Damping Ratio ◽  
Silty Sand ◽  
Freeze Thaw

Experimental Study on the Effect of Moisture Content on Hysteretic Behavior of Reinforced Concrete Columns

2018 ◽  
Vol 12 (1) ◽  
pp. 47-61
Author(s):  
Wenjuan Lv ◽  
Baodong Liu ◽  
Ming Li ◽  
Lin Li ◽  
Pengyuan Zhang
Keyword(s):  
Reinforced Concrete ◽  
Energy Dissipation ◽  
Moisture Content ◽  
Early Stage ◽  
Damping Ratio ◽  
Concrete Columns ◽  
Hysteretic Behavior ◽  
Cyclic Test ◽  
Experimental Result ◽  
Reinforced Concrete Columns

Background: For reinforced concrete structures under different humid conditions, the mechanical properties of concrete are significantly affected by the moisture content, which may result in a great change of the functional performance and bearing capacity. Objective: This paper presents an experiment to investigate the influence of the moisture content on the dynamic characteristics and hysteretic behavior of reinforced concrete column. Results: The results show that the natural frequency of reinforced concrete columns increases quickly at an early stage of immersion, but there is little change when the columns are close to saturation; the difference between the natural frequencies before and after cyclic test grows as the moisture content rises. The damping ratio slightly decreases first and then increases with the increase of moisture content; the damping ratio after the cyclic test is larger than before the test due to the development of the micro-cracks. Conclusion: The trend of energy dissipation is on the rise with increasing moisture content, although at an early stage, it decreases slightly. According to the experimental result, a formula for the moisture content on the average energy dissipation of reinforced concrete columns is proposed.

Beneficial performance of a quasi-zero stiffness vibration isolator with generalized geometric nonlinear damping

2020 ◽  
pp. 095745652097238
Author(s):  
Chun Cheng ◽  
Ran Ma ◽  
Yan Hu
Keyword(s):  
Damping Ratio ◽  
Nonlinear Damping ◽  
Vibration Isolator ◽  
Equivalent Damping ◽  
Frequency Responses ◽  
Geometric Nonlinear ◽  
Resonant Region ◽  
Force Transmissibility ◽  
Isolation Performance ◽  
Force And Displacement Transmissibility

Generalized geometric nonlinear damping based on the viscous damper with a non-negative velocity exponent is proposed to improve the isolation performance of a quasi-zero stiffness (QZS) vibration isolator in this paper. Firstly, the generalized geometric nonlinear damping characteristic is derived. Then, the amplitude-frequency responses of the QZS vibration isolator under force and base excitations are obtained, respectively, using the averaging method. Parametric analysis of the force and displacement transmissibility is conducted subsequently. At last, two phenomena are explained from the viewpoint of the equivalent damping ratio. The results show that decreasing the velocity exponent of the horizontal damper is beneficial to reduce the force transmissibility in the resonant region. For the case of base excitation, it is beneficial to select a smaller velocity exponent only when the nonlinear damping ratio is relatively large.

Response Law and Influencing Factors of the Soil under Action of Pile Driving Vibration Based on Midas/GTS

2013 ◽  
Vol 353-356 ◽  
pp. 979-983
Author(s):  
Dong Zhang ◽  
Jing Bo Su ◽  
Hui De Zhao ◽  
Hai Yan Wang
Keyword(s):  
Damping Ratio ◽  
Large Diameter ◽  
Time History ◽  
Pile Driving ◽  
Analysis Model ◽  
Vibration Load ◽  
History Analysis ◽  
Study Results ◽  
Propagation Law ◽  
Dynamic Time

Due to the upgrade and reconstruct of a high-piled wharf, the piling construction may cause the damage of the large diameter underground pipe of a power plant nearby. For this problem, a dynamic time-history analysis model was established using MIDAS/GTS program. Based on the analysis of the pile driving vibration and its propagation law, some parameters, such as the modulus of the soil, the Poissons ratio of soil, the action time of vibration load and the damping ratio of the soil that may have an effect on the response law of the soil, were studied. The study results not only serve as an important inference to the construction of this case, but also accumulate experience and data for other similar engineering practices.

Spectral damping scaling factors for horizontal components of ground motions from subduction earthquakes using NGA-Subduction data

2021 ◽  
pp. 875529302110279
Author(s):  
Sanaz Rezaeian ◽  
Linda Al Atik ◽  
Nicolas M Kuehn ◽  
Norman Abrahamson ◽  
Yousef Bozorgnia ◽  
...  
Keyword(s):  
Ground Motions ◽  
Damping Ratio ◽  
Spectral Shape ◽  
Parametric Models ◽  
Scaling Factors ◽  
Global Models ◽  
Motion Models ◽  
Subduction Earthquakes ◽  
Crustal Earthquakes ◽  
Subduction Zone Earthquakes

This article develops global models of damping scaling factors (DSFs) for subduction zone earthquakes that are functions of the damping ratio, spectral period, earthquake magnitude, and distance. The Next Generation Attenuation for subduction earthquakes (NGA-Sub) project has developed the largest uniformly processed database of recorded ground motions to date from seven subduction regions: Alaska, Cascadia, Central America and Mexico, South America, Japan, Taiwan, and New Zealand. NGA-Sub used this database to develop new ground motion models (GMMs) at a reference 5% damping ratio. We worked with the NGA-Sub project team to develop an extended database that includes pseudo-spectral accelerations (PSA) for 11 damping ratios between 0.5% and 30%. We use this database to develop parametric models of DSF for both interface and intraslab subduction earthquakes that can be used to adjust any subduction GMM from a reference 5% damping ratio to other damping ratios. The DSF is strongly influenced by the response spectral shape and the duration of motion; therefore, in addition to the damping ratio, the median DSF model uses spectral period, magnitude, and distance as surrogate predictor variables to capture the effects of the spectral shape and the duration of motion. We also develop parametric models for the standard deviation of DSF. The models presented in this article are for the RotD50 horizontal component of PSA and are compared with the models for shallow crustal earthquakes in active tectonic regions. Some noticeable differences arise from the considerably longer duration of interface records for very large magnitude events and the enriched high-frequency content of intraslab records, compared with shallow crustal earthquakes. Regional differences are discussed by comparing the proposed global models with the data from each subduction region along with recommendations on the applicability of the models.

scholarly journals Evaluation of Dynamic Properties of Sodium-Alginate-Reinforced Soil Using A Resonant-Column Test

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2743
Author(s):  
Seongnoh Ahn ◽  
Jae-Eun Ryou ◽  
Kwangkuk Ahn ◽  
Changho Lee ◽  
Jun-Dae Lee ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Sodium Alginate ◽  
Shear Failure ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Reinforced Soil ◽  
Resonant Column ◽  
Column Test ◽  
Alginate Solution ◽  
Resonant Column Test

Ground reinforcement is a method used to reduce the damage caused by earthquakes. Usually, cement-based reinforcement methods are used because they are inexpensive and show excellent performance. Recently, however, reinforcement methods using eco-friendly materials have been proposed due to environmental issues. In this study, the cement reinforcement method and the biopolymer reinforcement method using sodium alginate were compared. The dynamic properties of the reinforced ground, including shear modulus and damping ratio, were measured through a resonant-column test. Also, the viscosity of sodium alginate solution, which is a non-Newtonian fluid, was also explored and found to increase with concentration. The maximum shear modulus and minimum damping ratio increased, and the linear range of the shear modulus curve decreased, when cement and sodium alginate solution were mixed. Addition of biopolymer showed similar reinforcing effect in a lesser amount of additive compared to the cement-reinforced ground, but the effect decreased above a certain viscosity because the biopolymer solution was not homogeneously distributed. This was examined through a shear-failure-mode test.

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