Pub Date : 2023-05-29DOI: 10.1177/14613484231177651
Hou-lin Liu, Jianbin Hu, Zhoufeng He, Kai Wang, Xin-xin Lu
To broaden the database of fire equipment selection and provide the basis for its selection and optimization, a low specific speed centrifugal fire pump with a specific speed of 24.7 was selected as the research object, and the inlet and outlet pressure pulsation and cavitation characteristics under different flow rates were analyzed through experiments. Results show that the head of the fire pump under the design flow rate was 75.68 m, and the efficiency was 36.84%. The dominant frequency of the pressure pulsation in the inlet and outlet of the pump under different flow rates is 1 APF (axial passing frequency). The zero flow rate has no obvious peak distribution at 1 BPF (blade passing frequency). The secondary frequency of 1 BPF and the n times the harmonic frequency of 1 BPF are distributed in the outlet of the pump. The critical net positive suction head of the fire pump under 1.0 Qd and 1.5 Qd was 0.95 m and 2.38 m, respectively.
{"title":"Experimental research on pressure pulsation and cavitation characteristics of centrifugal fire pump","authors":"Hou-lin Liu, Jianbin Hu, Zhoufeng He, Kai Wang, Xin-xin Lu","doi":"10.1177/14613484231177651","DOIUrl":"https://doi.org/10.1177/14613484231177651","url":null,"abstract":"To broaden the database of fire equipment selection and provide the basis for its selection and optimization, a low specific speed centrifugal fire pump with a specific speed of 24.7 was selected as the research object, and the inlet and outlet pressure pulsation and cavitation characteristics under different flow rates were analyzed through experiments. Results show that the head of the fire pump under the design flow rate was 75.68 m, and the efficiency was 36.84%. The dominant frequency of the pressure pulsation in the inlet and outlet of the pump under different flow rates is 1 APF (axial passing frequency). The zero flow rate has no obvious peak distribution at 1 BPF (blade passing frequency). The secondary frequency of 1 BPF and the n times the harmonic frequency of 1 BPF are distributed in the outlet of the pump. The critical net positive suction head of the fire pump under 1.0 Qd and 1.5 Qd was 0.95 m and 2.38 m, respectively.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"50 1","pages":"1339 - 1349"},"PeriodicalIF":2.3,"publicationDate":"2023-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86482335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-22DOI: 10.1177/14613484231175626
Ye Jiang, Qiang Ma, Yanhong Bao
The traditional wave impeding block (WIB) is designed as composite multilayer WIB with the same thickness to improve its vibration isolation effect. Based on the wave theory in unsaturated porous medium and elastic medium, the isolation effect of composite multilayer WIB on P-wave in unsaturated soil is investigated, and the solution of the vertical displacement at surface after setting composite multilayer WIB (as an example for triple-layer) in unsaturated foundation is obtained. The key factors such as incidence angle, frequency, saturation, thickness, and burial depth of the composite multilayer WIB are evaluated on its vibration isolation properties. The results show that the optimum vibration isolation effect can be achieved by controlling the wave impedance ratio among layers of materials. The isolation efficiency of composite multilayer WIB is 33.9% higher than homogeneous WIB with same thickness at l east, and has good vibration isolation effect for low, medium, and high frequency.
{"title":"Isolation effect of composite multilayer wave impeding block on P-wave in unsaturated foundation","authors":"Ye Jiang, Qiang Ma, Yanhong Bao","doi":"10.1177/14613484231175626","DOIUrl":"https://doi.org/10.1177/14613484231175626","url":null,"abstract":"The traditional wave impeding block (WIB) is designed as composite multilayer WIB with the same thickness to improve its vibration isolation effect. Based on the wave theory in unsaturated porous medium and elastic medium, the isolation effect of composite multilayer WIB on P-wave in unsaturated soil is investigated, and the solution of the vertical displacement at surface after setting composite multilayer WIB (as an example for triple-layer) in unsaturated foundation is obtained. The key factors such as incidence angle, frequency, saturation, thickness, and burial depth of the composite multilayer WIB are evaluated on its vibration isolation properties. The results show that the optimum vibration isolation effect can be achieved by controlling the wave impedance ratio among layers of materials. The isolation efficiency of composite multilayer WIB is 33.9% higher than homogeneous WIB with same thickness at l east, and has good vibration isolation effect for low, medium, and high frequency.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"1 1","pages":"1482 - 1500"},"PeriodicalIF":2.3,"publicationDate":"2023-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76826158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-19DOI: 10.1177/14613484231155537
Mengmeng Zhang, Qiang Ma
Based on single-phase medium theory and unsaturated porous medium theory, the vibration isolation effect of setting a single-phase solid wave impeding block (WIB) in the unsaturated soil foundation under an underground dynamic load is investigated. Using the Fourier integral transform and Helmholtz vector decomposition, the calculation formula of the dynamic response of unsaturated soil foundation under an underground dynamic load is established by combining the boundary conditions. The influence of physical and mechanical parameters such as saturation, load frequency, embedded depth of WIB, thickness of WIB, and elastic modulus of WIB on the vibration isolation performance in unsaturated soil foundation is analyzed. The results show that in the case of underground dynamic load, setting a WIB in unsaturated soil foundation could achieve a better vibration isolation effect. The surface displacement amplitude decreases significantly with the increase of saturation, load frequency, embedded depth, thickness, and elastic modulus of WIB.
{"title":"Study on vibration isolation performance of wave impeding block in unsaturated soil foundation under an underground dynamic load","authors":"Mengmeng Zhang, Qiang Ma","doi":"10.1177/14613484231155537","DOIUrl":"https://doi.org/10.1177/14613484231155537","url":null,"abstract":"Based on single-phase medium theory and unsaturated porous medium theory, the vibration isolation effect of setting a single-phase solid wave impeding block (WIB) in the unsaturated soil foundation under an underground dynamic load is investigated. Using the Fourier integral transform and Helmholtz vector decomposition, the calculation formula of the dynamic response of unsaturated soil foundation under an underground dynamic load is established by combining the boundary conditions. The influence of physical and mechanical parameters such as saturation, load frequency, embedded depth of WIB, thickness of WIB, and elastic modulus of WIB on the vibration isolation performance in unsaturated soil foundation is analyzed. The results show that in the case of underground dynamic load, setting a WIB in unsaturated soil foundation could achieve a better vibration isolation effect. The surface displacement amplitude decreases significantly with the increase of saturation, load frequency, embedded depth, thickness, and elastic modulus of WIB.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"55 1","pages":"1466 - 1481"},"PeriodicalIF":2.3,"publicationDate":"2023-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80414564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-17DOI: 10.1177/14613484231174860
Yaorui Shen, Jianqin Fu, Jing-ping Liu
A model coupling Reynolds-averaged Navier-Stokes (RANS) method and linearized Navier-Stokes equations (LNSEs) was established in order to investigate the acoustic excitation and attenuation effect from a coupling perspective of time–space–frequency under various flow velocities and mass fractions of methane. Results show that the energy distribution of acoustic modes under high-frequency acoustic excitation is more uniform. The amplitude of the acoustic oscillation at a multiple coupling physical field is 10,000 times higher than that at simple flow field. The case when w C H 4 = 0.8 owns the largest percentage of energy conversion from fundamental to high-frequency signals, the largest percentage of transmitted waves from the combustion chamber system to outside and the strongest non-linear effect. When w C H 4 rises, the amplitude of oscillations at points and the attenuation effect of high-frequency signals along the axial are enhanced. At the case of Uin = 15 m/s, the amplitude of harmonics is reduced by 18% compared with other cases, while the proportion of the high-frequency harmonic increases, proving the non-linearity cannot be neglected in this case. As velocity rises, the energy conversion from fundamental to high-frequency signals enhances; while closer to the outlet position, the more complex the oscillation signal is. Model-shapes analysis shows that a case of w C H 4 = 0.8 owns the largest amplitude of the second harmonic at downstream of the burner, while the amplitude of the harmonics rapidly increases at Uin = 15 m/s at the end of the burner, which further indicates that the energy conversion of low-frequency signals to high-frequency signals occurs mainly in the middle and downstream regions.
为了从时空频耦合的角度研究不同流速和不同甲烷质量分数下的声激励和衰减效应，建立了reynolds -average Navier-Stokes (RANS)方法和线性化Navier-Stokes方程的耦合模型。结果表明，在高频声激励下，声模态的能量分布更为均匀。多耦合物理场下的声振荡幅值比简单流场下的声振荡幅值高10000倍。当wch = 0.8时，基频信号向高频信号的能量转换比例最大，燃烧室系统向外传输波的比例最大，非线性效应最强。当wc4h增大时，各点的振荡幅度和高频信号沿轴向的衰减作用增强。在Uin = 15 m/s的情况下，谐波幅值比其他情况降低了18%，而高频谐波的比例增加，证明了这种情况下的非线性是不可忽视的。随着速度的增加，基频信号向高频信号的能量转换增强;越靠近出口位置，振荡信号越复杂。模型形状分析表明，当w C H 4 = 0.8时，燃烧器下游二次谐波幅值最大，而在燃烧器末端Uin = 15 m/s时，二次谐波幅值迅速增大，进一步说明低频信号向高频信号的能量转换主要发生在中下游区域。
{"title":"Analysis of separating acoustics from the thermoacoustic system of methane combustion based on Reynolds-averaged Navier-Stokes and linearized Navier-Stokes equations","authors":"Yaorui Shen, Jianqin Fu, Jing-ping Liu","doi":"10.1177/14613484231174860","DOIUrl":"https://doi.org/10.1177/14613484231174860","url":null,"abstract":"A model coupling Reynolds-averaged Navier-Stokes (RANS) method and linearized Navier-Stokes equations (LNSEs) was established in order to investigate the acoustic excitation and attenuation effect from a coupling perspective of time–space–frequency under various flow velocities and mass fractions of methane. Results show that the energy distribution of acoustic modes under high-frequency acoustic excitation is more uniform. The amplitude of the acoustic oscillation at a multiple coupling physical field is 10,000 times higher than that at simple flow field. The case when w C H 4 = 0.8 owns the largest percentage of energy conversion from fundamental to high-frequency signals, the largest percentage of transmitted waves from the combustion chamber system to outside and the strongest non-linear effect. When w C H 4 rises, the amplitude of oscillations at points and the attenuation effect of high-frequency signals along the axial are enhanced. At the case of Uin = 15 m/s, the amplitude of harmonics is reduced by 18% compared with other cases, while the proportion of the high-frequency harmonic increases, proving the non-linearity cannot be neglected in this case. As velocity rises, the energy conversion from fundamental to high-frequency signals enhances; while closer to the outlet position, the more complex the oscillation signal is. Model-shapes analysis shows that a case of w C H 4 = 0.8 owns the largest amplitude of the second harmonic at downstream of the burner, while the amplitude of the harmonics rapidly increases at Uin = 15 m/s at the end of the burner, which further indicates that the energy conversion of low-frequency signals to high-frequency signals occurs mainly in the middle and downstream regions.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"20 1","pages":"1035 - 1054"},"PeriodicalIF":2.3,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86170441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-16DOI: 10.1177/14613484231176247
A. Galal, T. Amer, W. Amer, Heba Ali Elkafly
The current paper investigates the nonlinear dynamics of an excited pendulum by a crank-shaft-slider mechanism (CSSM), in which it is restricted to move vertically. He’s method of homotopy is employed to obtain the analytical solution of the governing differential equation. The numerical solution of this equation is obtained using the fourth-order Runge-Kutta method (RKM). The comparison between both solutions demonstrates a high level of consistency, which confirms the precision of the gained analytic solution. The graphical representations of these solutions are presented to reveal the influence of various parameters on the investigated motion.
{"title":"Dynamical analysis of a vertical excited pendulum using He’s perturbation method","authors":"A. Galal, T. Amer, W. Amer, Heba Ali Elkafly","doi":"10.1177/14613484231176247","DOIUrl":"https://doi.org/10.1177/14613484231176247","url":null,"abstract":"The current paper investigates the nonlinear dynamics of an excited pendulum by a crank-shaft-slider mechanism (CSSM), in which it is restricted to move vertically. He’s method of homotopy is employed to obtain the analytical solution of the governing differential equation. The numerical solution of this equation is obtained using the fourth-order Runge-Kutta method (RKM). The comparison between both solutions demonstrates a high level of consistency, which confirms the precision of the gained analytic solution. The graphical representations of these solutions are presented to reveal the influence of various parameters on the investigated motion.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"7 1","pages":"1328 - 1338"},"PeriodicalIF":2.3,"publicationDate":"2023-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84361855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-15DOI: 10.1177/14613484231176127
Wentao Zou, Ningdong Hu, Xue Yang, H. Hu
A high-precision equipment is very sensitive to vibration, even micro vibration. How to isolate the low-frequency broadband multidirectional vibration remains a challenge. As the main component of piezoelectric smart vibration isolation model, the piezoelectric stack consists of a piezoelectric actuator, a piezoelectric sensor, and a rubber layer. The numerical results obtained by the finite element method agree well with theoretical solutions. The vibration attenuates rapidly under displacement and velocity feedback control with negative gains. As the control gain decreases, the vibration isolation band is extended to lower frequency. A piezoelectric smart multidirectional vibration isolation platform model is further proposed by inclined installation of two piezoelectric stacks. A spring-like structure is designed to exert a preload pressure on these piezoelectric stacks. After optimization on the control gain, the platform can isolate vibration from 0 to 3000 Hz in multiple directions.
{"title":"Low-frequency broadband multidirectional vibration isolation by piezoelectric smart platform with active control","authors":"Wentao Zou, Ningdong Hu, Xue Yang, H. Hu","doi":"10.1177/14613484231176127","DOIUrl":"https://doi.org/10.1177/14613484231176127","url":null,"abstract":"A high-precision equipment is very sensitive to vibration, even micro vibration. How to isolate the low-frequency broadband multidirectional vibration remains a challenge. As the main component of piezoelectric smart vibration isolation model, the piezoelectric stack consists of a piezoelectric actuator, a piezoelectric sensor, and a rubber layer. The numerical results obtained by the finite element method agree well with theoretical solutions. The vibration attenuates rapidly under displacement and velocity feedback control with negative gains. As the control gain decreases, the vibration isolation band is extended to lower frequency. A piezoelectric smart multidirectional vibration isolation platform model is further proposed by inclined installation of two piezoelectric stacks. A spring-like structure is designed to exert a preload pressure on these piezoelectric stacks. After optimization on the control gain, the platform can isolate vibration from 0 to 3000 Hz in multiple directions.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"9 1","pages":"1451 - 1465"},"PeriodicalIF":2.3,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76339768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-11DOI: 10.1177/14613484231164970
R. Bahaadini, Mojtaba Javaheri, K. Majidi-Mozafari, Mohammad Azimi-Nejad
In this paper, the effects of porosity distribution and piezoelectric layers on the natural frequencies and flutter aerodynamic pressure of smart thick porous plates in supersonic airflow are studied. Based on the third-order shear deformation plate theory and first-order piston theory, thick functionally graded porous plates embedded by piezoelectric layers are investigated. The effective porous material properties, such as Young’s modulus and mass density are considered to vary along the thickness direction. The aeroelastic governing equations of motion are obtained using Hamilton’s principle and Maxwell’s equation. By applying Galerkin’s approach, the partial differential governing equations are transformed into a set of ordinary differential equations. The results indicate that the unsteady aerodynamic pressure and natural frequencies decrease as the porosity coefficient increases. Furthermore, the symmetric porosity distribution predicts the highest unsteady aerodynamic pressure and natural frequencies for porous plates. Besides, the results show that the porous plate enclosed by piezoelectric layers in open circuit condition has higher flutter aerodynamic pressure and natural frequencies than the similar plate in closed circuit condition.
{"title":"Effects of porosity distribution and piezoelectric layers on natural frequencies and unsteady aerodynamic pressure of smart thick porous plates","authors":"R. Bahaadini, Mojtaba Javaheri, K. Majidi-Mozafari, Mohammad Azimi-Nejad","doi":"10.1177/14613484231164970","DOIUrl":"https://doi.org/10.1177/14613484231164970","url":null,"abstract":"In this paper, the effects of porosity distribution and piezoelectric layers on the natural frequencies and flutter aerodynamic pressure of smart thick porous plates in supersonic airflow are studied. Based on the third-order shear deformation plate theory and first-order piston theory, thick functionally graded porous plates embedded by piezoelectric layers are investigated. The effective porous material properties, such as Young’s modulus and mass density are considered to vary along the thickness direction. The aeroelastic governing equations of motion are obtained using Hamilton’s principle and Maxwell’s equation. By applying Galerkin’s approach, the partial differential governing equations are transformed into a set of ordinary differential equations. The results indicate that the unsteady aerodynamic pressure and natural frequencies decrease as the porosity coefficient increases. Furthermore, the symmetric porosity distribution predicts the highest unsteady aerodynamic pressure and natural frequencies for porous plates. Besides, the results show that the porous plate enclosed by piezoelectric layers in open circuit condition has higher flutter aerodynamic pressure and natural frequencies than the similar plate in closed circuit condition.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"15 1","pages":"1117 - 1136"},"PeriodicalIF":2.3,"publicationDate":"2023-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83656063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-09DOI: 10.1177/14613484231174856
Ayman Abd-Elhamed, Soliman Alkhatib, M. Dagher
Machine foundations are subjected to significant dynamic impacts. These impacts could spread to the surrounding regions, affecting workers, sensitive equipment in the same institution, or nearby areas. This study analyzes the response of machine-supporting foundations to harmonic and explosive loads under operational conditions and provides closed-form solutions for predicting responses in terms of displacement, velocity, and acceleration time-histories to two common types of blast loads: a more accurate typical profile and simplified triangular profile. The soil-machine foundation system is regarded as a single-degree-of-freedom (SDOF) system that exhibits elastic–perfectly flexible resistance behavior. For the analysis of the SDOF system, two cases are considered: one assumes that the supporting soil keeps elastic during the explosion, and the peak displacement is less than the elastic one, while the other assumes that the blast occurs in an elastic state, and the peak displacement occurs in a plastic state. By using the closed-form analytical solutions, a detailed parametric analysis is carried out to evaluate the impacts of significant soil-foundation system characteristics such as mass, stiffness, and damping ratio on the response-time history of machine foundations. The findings are compared to those reported in the literature, and relevant conclusions are derived. Obtained results demonstrated that, despite its simplicity and usage of only positive phase to simulate blast loads, the simplified model’s response behavior differs significantly from the typical one. Furthermore, the derived solutions are utilized to design the foundations supporting vibrating machines for both harmonic and blast loads in a variety of conceivable scenarios depending on the blast magnitude.
{"title":"Closed-form solutions to investigate the nonlinear response of foundations supporting operating machines under blast loads","authors":"Ayman Abd-Elhamed, Soliman Alkhatib, M. Dagher","doi":"10.1177/14613484231174856","DOIUrl":"https://doi.org/10.1177/14613484231174856","url":null,"abstract":"Machine foundations are subjected to significant dynamic impacts. These impacts could spread to the surrounding regions, affecting workers, sensitive equipment in the same institution, or nearby areas. This study analyzes the response of machine-supporting foundations to harmonic and explosive loads under operational conditions and provides closed-form solutions for predicting responses in terms of displacement, velocity, and acceleration time-histories to two common types of blast loads: a more accurate typical profile and simplified triangular profile. The soil-machine foundation system is regarded as a single-degree-of-freedom (SDOF) system that exhibits elastic–perfectly flexible resistance behavior. For the analysis of the SDOF system, two cases are considered: one assumes that the supporting soil keeps elastic during the explosion, and the peak displacement is less than the elastic one, while the other assumes that the blast occurs in an elastic state, and the peak displacement occurs in a plastic state. By using the closed-form analytical solutions, a detailed parametric analysis is carried out to evaluate the impacts of significant soil-foundation system characteristics such as mass, stiffness, and damping ratio on the response-time history of machine foundations. The findings are compared to those reported in the literature, and relevant conclusions are derived. Obtained results demonstrated that, despite its simplicity and usage of only positive phase to simulate blast loads, the simplified model’s response behavior differs significantly from the typical one. Furthermore, the derived solutions are utilized to design the foundations supporting vibrating machines for both harmonic and blast loads in a variety of conceivable scenarios depending on the blast magnitude.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"13 1","pages":"1162 - 1187"},"PeriodicalIF":2.3,"publicationDate":"2023-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87401530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-29DOI: 10.1177/14613484231166523
C. Fang
This paper proposes a frequency domain-based analytical framework for seismic performance of viscously damped outrigger systems. Based on a core–outrigger–damper–column simplified model, the global dynamic stiffness matrix is assembled from the core modeled as a Timoshenko beam, damped outriggers as complex rotational stiffness comprising outriggers, dampers, and perimeter columns, and inherent damping using Leung’s theory and modal damping construction. A general numerical method combining Wittrick-Williams algorithm and Newtonian iteration is developed to study the dynamic characteristic of such systems with multiple damped outriggers. The fast Fourier transformation (FFT) and the inverse Fourier transformation (IFFT) are then integrated with the principle of potential energy to obtain the equivalent nodal force and thus the time history response by transformations between time and frequency domains. Finally, the stochastic analysis is conducted via the transfer function resulting from the global stiffness matrix with the stochastic seismic excitation following Kanai-Tajimi spectrum. The proposed approach is verified by comparison with the finite element method through a case study of a tall building implemented with viscously damped outriggers. This study shows that the proposed analytical framework could serve as a powerful tool for evaluating the performance of viscously damped outrigger systems.
{"title":"Frequency domain-based analytical framework for seismic performance of viscously damped outrigger systems based on continuous Timoshenko beam theory","authors":"C. Fang","doi":"10.1177/14613484231166523","DOIUrl":"https://doi.org/10.1177/14613484231166523","url":null,"abstract":"This paper proposes a frequency domain-based analytical framework for seismic performance of viscously damped outrigger systems. Based on a core–outrigger–damper–column simplified model, the global dynamic stiffness matrix is assembled from the core modeled as a Timoshenko beam, damped outriggers as complex rotational stiffness comprising outriggers, dampers, and perimeter columns, and inherent damping using Leung’s theory and modal damping construction. A general numerical method combining Wittrick-Williams algorithm and Newtonian iteration is developed to study the dynamic characteristic of such systems with multiple damped outriggers. The fast Fourier transformation (FFT) and the inverse Fourier transformation (IFFT) are then integrated with the principle of potential energy to obtain the equivalent nodal force and thus the time history response by transformations between time and frequency domains. Finally, the stochastic analysis is conducted via the transfer function resulting from the global stiffness matrix with the stochastic seismic excitation following Kanai-Tajimi spectrum. The proposed approach is verified by comparison with the finite element method through a case study of a tall building implemented with viscously damped outriggers. This study shows that the proposed analytical framework could serve as a powerful tool for evaluating the performance of viscously damped outrigger systems.","PeriodicalId":56067,"journal":{"name":"Journal of Low Frequency Noise Vibration and Active Control","volume":"20 1","pages":"1137 - 1161"},"PeriodicalIF":2.3,"publicationDate":"2023-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91266177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-28DOI: 10.1177/14613484231162447
A. Ismail, T. Amer, W. Amer
In this study, the motion of Lagrange’s gyro about its fixed point in the presence of a perturbed torque, a gyroscopic torque, and a varied restoring one is searched. We assume sufficiently small angular velocity components in the direction of the principal axes that differ from the dynamical symmetry one and a restoring torque that is considered to be greater than the perturbing one. In this manner, we replace the familiar small parameter that was used in previous works with a large one. In such cases, the gyro equations for motion (EOM) are formulated in the form of a two-degrees-of-freedom (DOF) autonomous system. We average the obtained system to get periodic solutions and motion’s geometric interpretation of the problem using the large parameter. The regular precession and the pure rotation of the motion are obtained. A numerical study is evaluated for asserted the used techniques and showed the influence of the changing parameters of motion on the gyro behavior. The trajectories of the motions and their stabilities are discussed and analyzed. The novelty of this work lies in how to adapt the method of large parameter (MLP) to solve the rigid body problem, especially since it has been assumed initially that its angular velocity or its initial energy are very small. MSC (2000): 70E20, 70E17, 70E15, 70E05
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