The LM-6 A new generation solid-liquid strap-on launch vehicle has the structural dynamic characteristics of lower frequencies,denser modes and coupling modes in longitudinal,bending and torsion modal space.During the...The LM-6 A new generation solid-liquid strap-on launch vehicle has the structural dynamic characteristics of lower frequencies,denser modes and coupling modes in longitudinal,bending and torsion modal space.During the development phase of LM-6 A,modal tests of partial stacks and the full vehicle were designed to obtain the structural dynamic properties.The structural dynamic models using the finite element method(FEM)have been verified and calibrated based on the modal test data.This paper describes the pre-test predictions and test execution,and details the comparison between the pre-test predictions and the test data.The successful maiden flight of LM-6 A further confirmed the effectiveness of structural dynamic modeling and modal test for LM-6 A.展开更多
To study the stiffness distribution of girder and the method to identify modal parameters of cable-stayed bridge, a simplified dynamical finite element method model named three beams model was established for the gird...To study the stiffness distribution of girder and the method to identify modal parameters of cable-stayed bridge, a simplified dynamical finite element method model named three beams model was established for the girder with double ribs. Based on the simplified model four stiffness formulae were deduced according to Hamilton principle. These formulae reflect well the contribution of the flexural, shearing, free torsion and restricted torsion deformation, respectively. An identification method about modal parameters was put forward by combining method of peak value and power spectral density according to modal test under ambient excitation. The dynamic finite element method analysis and modal test were carried out in a long-span concrete cable-stayed bridge. The results show that the errors of frequencies between theoretical analysis and test results are less than 10% mostly, and the most important modal parameters for cable-stayed bridge are determined to be the longitudinal floating mode, the first vertical flexural mode and the first torsional mode, which demonstrate that the method of stiffness distribution for three beams model is accurate and method to identify modal parameters is effective under ambient excitation modal test.展开更多
Many multi-story or highrise buildings consisting of a number of identical stories are usually considered as periodic spring-mass systems. The general expressions of natural frequencies, mode shapes, slopes and curvat...Many multi-story or highrise buildings consisting of a number of identical stories are usually considered as periodic spring-mass systems. The general expressions of natural frequencies, mode shapes, slopes and curvatures of mode shapes of the periodic spring-mass system by utilizing the periodic structure theory are derived in this paper. The sensitivities of these mode parameters with respect to structural damages, which do not depend on the physical parameters of the original structures, are obtained. Based on the sensitivity analysis of these mode parameters, a two-stage method is proposed to localize and quantify damages of multi-story or highrise buildings. The slopes and curvatures of mode shapes, which are highly sensitive to local damages, are used to localize the damages. Subsequently, the limited measured natural frequencies, which have a better accuracy than the other mode parameters, are used to quantify the extent of damages within the potential damaged locations. The experimental results of a 3-story experimental building demonstrate that the single or multiple damages of buildings, either slight or severe, can be correctly localized by using only the slope or curvature of mode shape in one of the lower modes, in which the change of natural frequency is the largest, and can be accurately quantified by the limited measured natural frequencies with noise pollution.展开更多
This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( ...This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( Venice,Italy). Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge and more than 20 modes were identified in the frequency range 0～10Hz. In the theoretical study,a 3D FE model of the bridge was developed using an integrated CAD-FEA approach; subsequently,the information obtained from the field tests,combined with simple manual tuning,provided a linear elastic model,accurately fitting the modal parameters of the bridge in its present condition.展开更多
Nonlinear behavior is important in the vibration test of engineering structures. In this study, a constant response vibration test is proposed for nonlinear element extraction. The method is based on the principle of ...Nonlinear behavior is important in the vibration test of engineering structures. In this study, a constant response vibration test is proposed for nonlinear element extraction. The method is based on the principle of Harmonic Balance Method (HBM). The stiffness or damping can be regarded as constant for particular steady displacement or velocity response. The displacement or velocity is controlled as a constant in the test. Then the measured Frequency Response Function(FRF) is obtained. The equivalent stiffness or damping is estimated using FRFs for a particular vibration response level. The displacement-dependent stiffness and velocity-dependent damping are fitted to describe the unknown non-linearity. The nonlinear spring and damping force can be obtained by combining the fitting results with HBM using first-order expansion. Constant response vibration test is illustrated through experimental setup to verify its effectiveness. Experimental results show that the procedure is capable of achieving an accurate parameter identification of nonlinear damping and stiffness, which is hopeful for industrial application.展开更多
近年来,随着车辆设计向轻量化、高强度化方向发展,边三轮车车架作为关键的承载结构,其性能直接影响车辆的整体强度和稳定性.车架在复杂工况下承受纵向弯曲、横向弯曲和扭转载荷,因此在设计车架过程中不仅需满足强度和刚度要求,还需确保...近年来,随着车辆设计向轻量化、高强度化方向发展,边三轮车车架作为关键的承载结构,其性能直接影响车辆的整体强度和稳定性.车架在复杂工况下承受纵向弯曲、横向弯曲和扭转载荷,因此在设计车架过程中不仅需满足强度和刚度要求,还需确保车架长期使用的可靠性与安全性.有限元分析(Finite element analysis,FEA)作为一种高效的结构性能研究手段,能够通过精确建模和仿真分析对车架在静态和动态载荷作用下的应力分布、变形及振动特性进行全面评估,从而为结构性能的验证提供理论依据和数据支持.相较于传统经验设计与试验验证方法,有限元分析具有高效性和精确性的优势,已广泛应用于车架结构的设计和分析.然而,现有研究多集中于车架的轻量化设计,对于标准载荷条件下对既有设计的性能验证研究较为稀缺.本研究针对某边三轮车架,基于ANSYS Workbench有限元分析软件对其结构性能进行系统验证.首先,采用APDL语言编写参数化建模命令流,建立了车架的三维模型,并对非承载部分进行了合理简化处理,以提高计算效率;其次,通过静力学分析,评估车架在设计载荷下的应力分布和变形情况,验证其强度设计的合理性;再次,通过模态分析获取车架的前六阶固有频率和振型,评估其动态特性及共振风险;最后,结合路面振动台架试验,验证车架在实际振动环境下的稳定性和耐久性.本研究旨在验证现有设计的合理性,为边三轮车架在实际工况下的强度和动态性能提供科学评估,同时为类似结构的设计与工程应用提供重要参考.展开更多
The wheel-rail dynamic load(WRL)and its vibration energy transfer(VET)are foundational for studying ballastless track dynamics in high-speed railways.In this study,the higher-order modal parameters of track beds with ...The wheel-rail dynamic load(WRL)and its vibration energy transfer(VET)are foundational for studying ballastless track dynamics in high-speed railways.In this study,the higher-order modal parameters of track beds with different isolating layers were identified experimentally and a vehicle-track coupled dynamic model considering track bed broadband vibrations(TBBVs)was established.The WRL and its VET were investigated,and the contribution law as well as the influence mechanism of TBBVs on them was determined.The results showed the WRL and track bed vibration energy exhibited significant resonances,with more prominent high-frequency resonance peaks in the track bed vibration energy.TBBVs had a significant effect on low-frequency WRLs,and markedly influenced the VET across various frequency bands.Intense low-frequency and weak high-frequency intermodulation effects between the wheel-rail and track beds were observed.The effect of track bed vibrations can be disregarded when focusing on high-frequency WRLs above 200 Hz.Variations in the isolating layer stiffness have more significant effects on the track bed vibration energy than the WRL.Rational stiffness of the isolating layer should be selected to avoid mode-coupling resonance from track beds to the wheel-rail subsystem.展开更多
文摘The LM-6 A new generation solid-liquid strap-on launch vehicle has the structural dynamic characteristics of lower frequencies,denser modes and coupling modes in longitudinal,bending and torsion modal space.During the development phase of LM-6 A,modal tests of partial stacks and the full vehicle were designed to obtain the structural dynamic properties.The structural dynamic models using the finite element method(FEM)have been verified and calibrated based on the modal test data.This paper describes the pre-test predictions and test execution,and details the comparison between the pre-test predictions and the test data.The successful maiden flight of LM-6 A further confirmed the effectiveness of structural dynamic modeling and modal test for LM-6 A.
基金Project(50608008) supported by the National Natural Science Foundation of Chinaproject(20050536002) supported by the Specialized Research Fund for the Doctoral Program of Higher Education
文摘To study the stiffness distribution of girder and the method to identify modal parameters of cable-stayed bridge, a simplified dynamical finite element method model named three beams model was established for the girder with double ribs. Based on the simplified model four stiffness formulae were deduced according to Hamilton principle. These formulae reflect well the contribution of the flexural, shearing, free torsion and restricted torsion deformation, respectively. An identification method about modal parameters was put forward by combining method of peak value and power spectral density according to modal test under ambient excitation. The dynamic finite element method analysis and modal test were carried out in a long-span concrete cable-stayed bridge. The results show that the errors of frequencies between theoretical analysis and test results are less than 10% mostly, and the most important modal parameters for cable-stayed bridge are determined to be the longitudinal floating mode, the first vertical flexural mode and the first torsional mode, which demonstrate that the method of stiffness distribution for three beams model is accurate and method to identify modal parameters is effective under ambient excitation modal test.
基金Project supported by the National Natural Science Foundation of China (No. 50378041) Specialized Research Fund for Doctoral Programs of Higher Education (No. 20030487016).
文摘Many multi-story or highrise buildings consisting of a number of identical stories are usually considered as periodic spring-mass systems. The general expressions of natural frequencies, mode shapes, slopes and curvatures of mode shapes of the periodic spring-mass system by utilizing the periodic structure theory are derived in this paper. The sensitivities of these mode parameters with respect to structural damages, which do not depend on the physical parameters of the original structures, are obtained. Based on the sensitivity analysis of these mode parameters, a two-stage method is proposed to localize and quantify damages of multi-story or highrise buildings. The slopes and curvatures of mode shapes, which are highly sensitive to local damages, are used to localize the damages. Subsequently, the limited measured natural frequencies, which have a better accuracy than the other mode parameters, are used to quantify the extent of damages within the potential damaged locations. The experimental results of a 3-story experimental building demonstrate that the single or multiple damages of buildings, either slight or severe, can be correctly localized by using only the slope or curvature of mode shape in one of the lower modes, in which the change of natural frequency is the largest, and can be accurately quantified by the limited measured natural frequencies with noise pollution.
基金support provided by the Italian Ministry of University and Research,under the grant PRIN 2006
文摘This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( Venice,Italy). Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge and more than 20 modes were identified in the frequency range 0～10Hz. In the theoretical study,a 3D FE model of the bridge was developed using an integrated CAD-FEA approach; subsequently,the information obtained from the field tests,combined with simple manual tuning,provided a linear elastic model,accurately fitting the modal parameters of the bridge in its present condition.
文摘Nonlinear behavior is important in the vibration test of engineering structures. In this study, a constant response vibration test is proposed for nonlinear element extraction. The method is based on the principle of Harmonic Balance Method (HBM). The stiffness or damping can be regarded as constant for particular steady displacement or velocity response. The displacement or velocity is controlled as a constant in the test. Then the measured Frequency Response Function(FRF) is obtained. The equivalent stiffness or damping is estimated using FRFs for a particular vibration response level. The displacement-dependent stiffness and velocity-dependent damping are fitted to describe the unknown non-linearity. The nonlinear spring and damping force can be obtained by combining the fitting results with HBM using first-order expansion. Constant response vibration test is illustrated through experimental setup to verify its effectiveness. Experimental results show that the procedure is capable of achieving an accurate parameter identification of nonlinear damping and stiffness, which is hopeful for industrial application.
文摘近年来,随着车辆设计向轻量化、高强度化方向发展,边三轮车车架作为关键的承载结构,其性能直接影响车辆的整体强度和稳定性.车架在复杂工况下承受纵向弯曲、横向弯曲和扭转载荷,因此在设计车架过程中不仅需满足强度和刚度要求,还需确保车架长期使用的可靠性与安全性.有限元分析(Finite element analysis,FEA)作为一种高效的结构性能研究手段,能够通过精确建模和仿真分析对车架在静态和动态载荷作用下的应力分布、变形及振动特性进行全面评估,从而为结构性能的验证提供理论依据和数据支持.相较于传统经验设计与试验验证方法,有限元分析具有高效性和精确性的优势,已广泛应用于车架结构的设计和分析.然而,现有研究多集中于车架的轻量化设计,对于标准载荷条件下对既有设计的性能验证研究较为稀缺.本研究针对某边三轮车架,基于ANSYS Workbench有限元分析软件对其结构性能进行系统验证.首先,采用APDL语言编写参数化建模命令流,建立了车架的三维模型,并对非承载部分进行了合理简化处理,以提高计算效率;其次,通过静力学分析,评估车架在设计载荷下的应力分布和变形情况,验证其强度设计的合理性;再次,通过模态分析获取车架的前六阶固有频率和振型,评估其动态特性及共振风险;最后,结合路面振动台架试验,验证车架在实际振动环境下的稳定性和耐久性.本研究旨在验证现有设计的合理性,为边三轮车架在实际工况下的强度和动态性能提供科学评估,同时为类似结构的设计与工程应用提供重要参考.
基金supported by the National Natural Science Foundation of China(No.52308468)the China Postdoctoral Science Foundation(No.2022M723390)the Jiangsu Provincial Excellent Postdoctoral Program(No.2023ZB020),China.
文摘The wheel-rail dynamic load(WRL)and its vibration energy transfer(VET)are foundational for studying ballastless track dynamics in high-speed railways.In this study,the higher-order modal parameters of track beds with different isolating layers were identified experimentally and a vehicle-track coupled dynamic model considering track bed broadband vibrations(TBBVs)was established.The WRL and its VET were investigated,and the contribution law as well as the influence mechanism of TBBVs on them was determined.The results showed the WRL and track bed vibration energy exhibited significant resonances,with more prominent high-frequency resonance peaks in the track bed vibration energy.TBBVs had a significant effect on low-frequency WRLs,and markedly influenced the VET across various frequency bands.Intense low-frequency and weak high-frequency intermodulation effects between the wheel-rail and track beds were observed.The effect of track bed vibrations can be disregarded when focusing on high-frequency WRLs above 200 Hz.Variations in the isolating layer stiffness have more significant effects on the track bed vibration energy than the WRL.Rational stiffness of the isolating layer should be selected to avoid mode-coupling resonance from track beds to the wheel-rail subsystem.
