The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hong Hao - One of the best experts on this subject based on the ideXlab platform.
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experimental study on Relative Displacement responses of bridge frames subjected to spatially varying ground motion and its mitigation using superelastic sma restrainers
Soil Dynamics and Earthquake Engineering, 2018Co-Authors: Bipin Shrestha, Hong Hao, Weixin RenAbstract:Abstract Contemporary bridge codes recommend adjusting the fundamental frequencies of adjacent segments close to each other to mitigate Relative Displacement induced damages arising during the strong seismic events. Previous studies revealed that such recommendation leads to effective mitigation of damages on the bridge structures subjected to uniform ground motions. However, in an elongated bridge structure spatial variations of earthquake ground motions at different supports are inevitable which can result in larger Relative Displacements. This study presents experimental results from a large-scale (1/6) shake table testing of bridge models with two bridge frames having a total length of 16.67 m, subjected to spatially varying ground motions. Experiments were also carried out with bridge model with superelastic Shape Memory Alloy (SMA) restrainers to evaluate its effectiveness on mitigating bridge responses. It is revealed that even the adjacent bridge frames with fundamental frequencies close to each other are susceptible to the localized damages at the joints due to poundings, which could lead to delayed access to the affected sites after an earthquake. Superelastic SMA restrainers could effectively reduce the opening Relative Displacement and pounding intensity. Moreover, owing to its superelastic behaviour the restrainers would not require replacement even after strong seismic events. Finally, numerical models of the bridge were developed and parametric studies were performed to comprehend the results of the experiment.
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health monitoring of joint conditions in steel truss bridges with Relative Displacement sensors
Measurement, 2016Co-Authors: Hong HaoAbstract:Abstract This paper investigates the feasibility and effectiveness of using a recently developed Relative Displacement sensor for the structural health monitoring of joint conditions in steel truss bridges. The developed Relative Displacement sensor is an innovative design offering some advantages and unique features, and is a much easier and economical method for structural health monitoring due to the simplicity of its direct measurement of Relative Displacement without the requirement for a stable reference point. To investigate the performance of applying the developed Relative Displacement sensors for structural joint condition monitoring, a steel truss bridge model is fabricated in the laboratory and installed with the Relative Displacement sensors to detect the health conditions of joint connections. The dynamic Relative Displacement measurements are analyzed with a time-frequency analysis method, i.e. continuous wavelet transform, which is a well-practiced signal processing technique to identify the structural condition change, namely the loosen bolt damage in the joint connection of steel truss bridges under ambient vibrations. The sensitivity range of the developed sensor is also investigated to see how sensitive the sensor is to identify the local bolt damage. Relative Displacement measurements of the steel truss bridge models under free vibration tests from both undamaged and damaged states are also analyzed, and a damage index based on the change in the percentages of a specific wavelet packet component to the total wavelet packet energy between the undamaged and damaged states is used to detect the existence of the loosen bolt damage in steel truss bridges. Experimental studies demonstrate that the developed Relative Displacement sensor has a sensitive performance to identify and assess the joint conditions in steel truss bridges.
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damage detection of shear connectors under moving loads with Relative Displacement measurements
Mechanical Systems and Signal Processing, 2015Co-Authors: Jun Li, Hong HaoAbstract:Abstract This paper investigates the use of Relative Displacement measurements from the newly developed Relative Displacement sensors to identify the damage of shear connectors in composite bridges. Continuous Wavelet Transform and Hilbert–Huang Transform are applied to analyze the measured dynamic responses and to identify the damage of shear connectors in the composite bridge model under moving loads. Comparative studies by using the Relative Displacement, acceleration and Displacement measurements respectively for the damage detection are conducted. A comparative study of using Relative Displacements and acceleration responses of the bridge under ambient excitations to monitor the shear connector conditions is also conducted. Numerical and experimental studies demonstrate that both Relative Displacement and acceleration measurements can identify the location and the instant of damage occurrence in shear connectors when the bridge is under moving loads. The results demonstrate that Relative Displacement is a better response quantity for structural health monitoring of composite bridges.
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spatial ground motion effect on Relative Displacement of adjacent building structures
Earthquake Engineering & Structural Dynamics, 1999Co-Authors: Hong Hao, Serong ZhangAbstract:This paper analyses earthquake ground motion spatial variation effects on Relative linear elastic response of adjacent building structures. It studies the Relative importance of ground motion spatial variations and dynamic characteristics of adjacent structures in causing Relative responses. Random vibration method is used in the study. It is found that, besides ground-acceleration-induced dynamic responses, quasi-static responses induced by spatially varying ground Displacements also contribute significantly to the Relative structural responses. The effects of spatial ground motions are very pronounced to the Relative Displacements of adjacent low-rise structures, and to those of high-rise adjacent structures with similar vibration characteristics. The effect of vibration properties of adjacent structures are, however, more significant to those of high-rise adjacent structures if they poses noticeably different vibration periods. Copyright © 1999 John Wiley & Sons, Ltd.
Hiroshi Mori - One of the best experts on this subject based on the ideXlab platform.
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local structure and mean square Relative Displacement in sio2 and geo2 polymorphs
Journal of Synchrotron Radiation, 1999Co-Authors: Akira Yoshiasa, Takuo Tamura, O Kamishima, Keiichiro Murai, Kiyoshi Ogata, Hiroshi MoriAbstract:Extended X-ray absorption fine structure (EXAFS) spectra near the Si and Ge K-edge for SiO_2 and GeO_2 polymorphs were measured in transmission mode with synchrotron radiation at the Photon Factory, Tsukuba. The local structures and mean-square Relative Displacements were determined in \alpha-tridymite, \alpha-quartz and stishovite. In stishovite, Si is octahedrally coordinated and the four coplanar Si—O bonds [1.755 (8) A] are shorter than the other two axial bonds [1.813 (15) A]. The high-temperature phase tridymite [1.597 (3) A] has a smaller local bond distance than \alpha-quartz [1.618 (5) A]. The temperature variation of the local structural parameters for quartz-type GeO_2 (q-GeO_2) and rutile-type GeO_2 (r-GeO_2) have been determined in the temperature range 7–1000 K. The harmonic effective interatomic potential V(u)=\alpha{u}^2/2 was evaluated from the contribution to the thermal vibration, where u is the deviation of the bond distance from the location of the potential minimum. The potential coefficient \alpha for the Ge—O bond of the tetrahedron in q-GeO_2 is 24.6 eV A−2. The potential coefficients \alpha for the four coplanar Ge—O bonds and the two axial bonds of the octahedron in r-GeO_2 are 12.9 and 14.9 eV A−2, respectively. The potential coefficient \alpha for the second-nearest Ge—Ge distance in q-GeO_2 is 9.57 eV A−2. The potential coefficients \alpha for the second- and third-nearest Ge—Ge distances in r-GeO_2 are 11.6 and 7.18 eV A−2, respectively. The effective interatomic potential is largely influenced by the local structure, particularly by the coordination numbers. The phonon dispersion relations for q-GeO_2 and r-GeO_2 were estimated along [100] by calculating the dynamical matrix using the potential coefficients \alpha for the Ge—O and Ge—Ge motions. The quartz-type structure has a more complex structure with a wide gap between 103 and 141 meV and a highest energy of 149 meV, whereas the rutile-type structure has a continuous distribution and a highest energy of 126 meV.
Glenn R. Heppler - One of the best experts on this subject based on the ideXlab platform.
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semi active vibration control schemes for suspension systems using magnetorheological dampers
Journal of Vibration and Control, 2006Co-Authors: Y. Shen, M. Farid Golnaraghi, Glenn R. HepplerAbstract:Three semi-active control methods are investigated for use in a suspension system using a commer- cial magnetorheological damper. The three control methods are the limited Relative Displacement method, the modified skyhook method, and the modified Rakheja-Sankar method. The method of averaging has been adopted to provide an analytical platform for analyzing the performance of the different control methods. The analytical results are verified using numerical simulation, and further are used to assess the efficiency of dif- ferent control methods. An experimental test bed has been developed to examine the three control methods under sinusoidal and random excitations. Both analytical and experimental results confirm that the Rakheja- Sankar control and modified skyhook control methods significantly reduce the root-mean-square response of both the acceleration and Relative Displacement of the sprung mass, while the limited Relative Displacement controller can only control the Relative Displacement of the suspension system.
Pengzhi Pan - One of the best experts on this subject based on the ideXlab platform.
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the influence of infilling conditions on flaw surface Relative Displacement induced cracking behavior in hard rock
Rock Mechanics and Rock Engineering, 2020Co-Authors: Pengzhi Pan, Shuting Miao, Quan Jiang, Changyue ShaoAbstract:The Relative tangential Displacement (or slip) and Relative normal Displacement of flaw surfaces are two of the main factors driving crack initiation and propagation of rocks. In this study, uniaxial compression experiments are performed in flawed marble under different cases, i.e., open flaw and flaw filled by gypsum, cement and resin, and different flaw inclinations, to study the influence of infilling conditions on the flaw surface Relative Displacement (i.e., Relative tangential and normal Displacement) and the induced cracking behaviors, such as crack initiation, propagation and crack patterns. The digital image correlation (DIC) technique is used to trace the evolution of Relative deformation across the flaw surface and cracking process of flawed specimens. The results reveal that the difference in flaw surface Relative Displacement, at a given load, is introduced by different infilling materials. Among the four types of flaws, the filled flaw with smaller Relative Displacement is less likely to initiate cracks than the unfilled flaw with larger Relative Displacement. Moreover, the crack initiation position, angle, and types are also dependent on the Relative deformation between the flaw surfaces. With the increase of the stiffness of the filler or flaw inclination angle, the effect of Relative normal Displacement on the cracking behavior is weakened, while the effect of Relative tangential Displacement increasingly dominates. As a result, the filled flaw with smaller Relative normal Displacement makes wing crack initiation points closer to flaw tips. Moreover, the filler with higher stiffness makes the wing crack initiation angle smaller, improves the possibility of the quasi-coplanar crack initiation, and suppresses the initiation of anti-wing cracks from the flaw tips in hard rock.
Akira Yoshiasa - One of the best experts on this subject based on the ideXlab platform.
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local structure and mean square Relative Displacement in sio2 and geo2 polymorphs
Journal of Synchrotron Radiation, 1999Co-Authors: Akira Yoshiasa, Takuo Tamura, O Kamishima, Keiichiro Murai, Kiyoshi Ogata, Hiroshi MoriAbstract:Extended X-ray absorption fine structure (EXAFS) spectra near the Si and Ge K-edge for SiO_2 and GeO_2 polymorphs were measured in transmission mode with synchrotron radiation at the Photon Factory, Tsukuba. The local structures and mean-square Relative Displacements were determined in \alpha-tridymite, \alpha-quartz and stishovite. In stishovite, Si is octahedrally coordinated and the four coplanar Si—O bonds [1.755 (8) A] are shorter than the other two axial bonds [1.813 (15) A]. The high-temperature phase tridymite [1.597 (3) A] has a smaller local bond distance than \alpha-quartz [1.618 (5) A]. The temperature variation of the local structural parameters for quartz-type GeO_2 (q-GeO_2) and rutile-type GeO_2 (r-GeO_2) have been determined in the temperature range 7–1000 K. The harmonic effective interatomic potential V(u)=\alpha{u}^2/2 was evaluated from the contribution to the thermal vibration, where u is the deviation of the bond distance from the location of the potential minimum. The potential coefficient \alpha for the Ge—O bond of the tetrahedron in q-GeO_2 is 24.6 eV A−2. The potential coefficients \alpha for the four coplanar Ge—O bonds and the two axial bonds of the octahedron in r-GeO_2 are 12.9 and 14.9 eV A−2, respectively. The potential coefficient \alpha for the second-nearest Ge—Ge distance in q-GeO_2 is 9.57 eV A−2. The potential coefficients \alpha for the second- and third-nearest Ge—Ge distances in r-GeO_2 are 11.6 and 7.18 eV A−2, respectively. The effective interatomic potential is largely influenced by the local structure, particularly by the coordination numbers. The phonon dispersion relations for q-GeO_2 and r-GeO_2 were estimated along [100] by calculating the dynamical matrix using the potential coefficients \alpha for the Ge—O and Ge—Ge motions. The quartz-type structure has a more complex structure with a wide gap between 103 and 141 meV and a highest energy of 149 meV, whereas the rutile-type structure has a continuous distribution and a highest energy of 126 meV.
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the mean square Relative Displacement and Displacement correlation functions in tetrahedrally and octahedrally coordinated anb8 n crystals
Japanese Journal of Applied Physics, 1997Co-Authors: Akira Yoshiasa, Kichiro Koto, Hironobu Maeda, Tadao IshiiAbstract:The Debye-Waller factors of atoms in Ge, GaN, ZnO, CdS, CdSe, CuBr, CuCl, AgI, CdO, AgBr, KBr and RbCl in order of Phillips ionicity (f i) are studied by both EXAFS and the diffraction method. The Displacement correlation functions (DCF) are derived from the mean-square Relative Displacement (MSRD) and the mean-square Displacement (MSD) at room temperature. The magnitudes of the MSRD and MSD correlate well with the coordination number and ionicity. The MSRDs of tetrahedrally coordinated compounds show a gradual approach to those of octahedrally coordinated ones as the ionicity increases. A divergent-like curve toward f i=0.785 is observed for the MSD in the tetrahedrally coordinated compounds, which indicates the behavior of lattice instability. In the tetrahedrally coordinated covalent materials, the MSRD is nearly half the MSD cation or MSD anion and the ratio of the DCF to MSD given by 2DCF/(MSD cation+MSD anion) is about 80%. In the octahedrally coordinated ionic materials, the MSRD is comparable to the MSD and 2DCF/(MSD cation+MSD anion)=50%. An anharmonic contribution to the Debye-Waller factor determined by EXAFS appears pronouncedly when the magnitude of σ(2) is greater than 0.01 A2. The MSRD for the tetrahedrally coordinated compounds of silver and copper halides obeys the systematic ionicity dependence and pronounced specificity of anharmonicity was not observed: AgI, CuBr and CuCl of which the high-temperature forms are typical superionic conductors have a broad interatomic potential which is similar to that of the octahedrally coordinated compounds and strongly correlated Displacement in thermal vibration between cation and anion.
