Identification of Multi-Axial Seismic Loadings from Several Structural Dynamic Responses

2012 ◽  
Vol 204-208 ◽  
pp. 2483-2487
Author(s):  
Kun Zhang ◽  
Hui Li ◽  
Zhong Dong Duan ◽  
Siu Seong Law
Keyword(s):  
Degrees Of Freedom ◽  
Least Squares Method ◽  
Three Dimensional ◽  
Dynamic Responses ◽  
Frame Structure ◽  
Model Errors ◽  
Structural Dynamic ◽  
Seismic Loadings ◽  
Seismic Accelerations ◽  
Damped Least Squares

A new method is proposed to identify multi-axial seismic loadings from structural dynamic responses on limited degrees of freedom. The seismic loadings acting on structures are modeled by Hartley series approximation, and the sensitivities of structural dynamic response with respect to the unknown approximation coefficients are derived. The identification equation is set up based on best fitting structural measured and calculated responses, and is solved with the damped least-squares method. A five-story three-dimensional steel frame structure excited by El-Centro seismic accelerations is studied for validating the proposed method. Numerical simulations with measurement noise and model errors show that the proposed method can accurately identify all seismic loadings from only several responses of the structure.

scholarly journals Vibration Control of Tower Structure with Multiple Cardan Gyroscopes

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Haoxiang He ◽  
Xin Xie ◽  
Wentao Wang
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Control ◽  
Dynamic Responses ◽  
Structural Vibration ◽  
Structural Dynamic ◽  
Torsion Effect ◽  
Tower Structure ◽  
Rotational Degrees Of Freedom ◽  
Earthquake Action ◽  
Control Equation

Tower structure is sensitive to hurricane and earthquake, and it is easy to generate large deflection and dynamic response. The multiple cardan gyroscope has two rotational degrees of freedom, which can generate strong moments to constrain the two horizontal orthogonal deflections if the rotor operates in high speeds, so the structural dynamic responses can be decreased. Hence, the method of dynamic control of the tower structure under wind load and earthquake action is proposed by using the multiple cardan gyroscopes as the dampers. The dynamic mechanism and the fixed axis principle of the multiple cardan gyroscope are introduced, and the dynamic equation of the gyroscope is established. The damping mechanism of the gyroscope is also described. For the tower structure equipped with the multiple cardan gyroscope dampers, the multidimensional control equation considering torsion effect is established, and the equivalent state space equation is presented. Taking a TV Tower with a number of gyroscope dampers as an analysis example, the structural dynamic responses and damping performance under fluctuating wind loads and earthquake action is studied. The results show that the multiple cardan gyroscope dampers with suitable parameters can effectively decrease the structural vibration in horizontal directions and torsional direction.

Large Scale Dynamic Response Analysis of Rod Bundles in Fluid Using Partitioned Coupling Technique

2011 ◽  
Author(s):  
Shunji Kataoka ◽  
Satsuki Minami ◽  
Hiroshi Kawai ◽  
Shinobu Yoshimura
Keyword(s):  
Degrees Of Freedom ◽  
Large Scale ◽  
Three Dimensional ◽  
Dynamic Responses ◽  
Coupled Analysis ◽  
Response Analysis ◽  
Dynamic Interactions ◽  
Coupling Technique ◽  
Structure Interaction ◽  
Preconditioned Iterative

Dynamic responses considering fluid structure interaction (FSI) is important in many engineering fields and some of the FSI phenomena are treated as an acoustic fluid and structure interaction (AFSI) problem. The dynamic interactions between the fluid and structure can change dynamic characteristics of structures and their responses to external excitation such as seismic loading. The authors have developed a coupled simulation system for the large scale AFSI problems using an iterative partitioned coupling technique. In the system, the authors employed ADVENTURE system which adopted an efficient preconditioned iterative linear algebraic solver, and ADVENTURE Coupler is used to handle interface variable efficiently on various parallel computational environments. The authors employ Broyden method for updating interface accelerations to obtain the robust and fast convergence property of fixed point iterations. This paper presents the overview of the coupled analysis system and the results of its application to several AFSI problems are shown. The system runs efficiently in a parallel environment and it is capable for analyses of complex shaped three dimensional structures with more than 20 million degrees of freedom model.

scholarly journals Assessment of Prestress Force in Bridges Using Structural Dynamic Responses under Moving Vehicles

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Hao Li ◽  
Zhongrong Lv ◽  
Jike Liu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Model Updating ◽  
Shell Element ◽  
Element Model ◽  
Dynamic Responses ◽  
Penalty Function Method ◽  
Structural Dynamic ◽  
Moving Vehicle

This study carries out numerical simulations to identify the magnitude of prestress force in a highway bridge by making use of the dynamic responses from moving vehicular loads. The prestressed bridges are modeled using four-node isoparametric flat shell element taking into account the transverse shearing deformation in the finite element model. The vehicle is modeled as a multiple degrees-of-freedom system. An approach based on dynamic response sensitivity-based finite element model updating is proposed to identify the elemental prestress force. The identified results are obtained iteratively with the penalty function method with regularization from the measured structural dynamic responses. A single-span prestressed Tee beam and two-span prestressed box-girder bridge are studied as two numerical examples. The effects of road surface roughness, measurement noise, and speed of moving vehicle on the identification results are investigated. Studies indicate that the proposed method is efficient and robust for prestress force identification. Good identified results can be obtained from several measured acceleration responses.

Identification of Local Time-Varying Systems Based on Dynamic Response Sensitivity

2012 ◽  
Vol 166-169 ◽  
pp. 3379-3382
Author(s):  
Kun Zhang ◽  
Hui Li ◽  
Zhong Dong Duan ◽  
S. S Law
Keyword(s):  
Dynamic Response ◽  
Local Time ◽  
Least Squares Method ◽  
Linear Time ◽  
Order Approximation ◽  
Time Varying ◽  
Structural Dynamic ◽  
Response Sensitivity ◽  
Damped Least Squares ◽  
Output Information

A new method based on dynamic response sensitivity is proposed for the identification of local linear time-varying (LTV) system. The unknown local LTV structural stiffness is modeled by orthogonal polynomial approximations, and the sensitivities of structural dynamic response with respect to orthogonal coefficients are derived. The identification equation is set up based on Taylor’s first order approximation, and is solved with the damped least-squares method. A fifteen-story shear building is studied to validate the proposed method. Three ideal cases of LTV systems, with periodically, abruptly and randomly varying stiffness at the 8th story of the structure, are investigated to illustrate the capability of the algorithm to track the variations of the systems. Numerical simulation with noisy measured accelerations shows that the proposed method can accurately identify various kinds of local time-varying system from only several responses of the structure. This method provides a new approach for detecting local time-varying stiffness of structures with incomplete measured output information.

scholarly journals Lightweight framework of shell models utilizing local heat sensors

2018 ◽  
Vol 14 (11) ◽  
pp. 155014771881130
Author(s):  
Shengfa Wang ◽  
Longfei Zhang ◽  
Baojun Li ◽  
Zhongxuan Luo
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Local Heat ◽  
Heat Diffusion ◽  
Frame Structure ◽  
Thickness Variation ◽  
Research Subjects ◽  
Lightweight Framework ◽  
Shell Models ◽  
Heat Sensor

Lightweight is one of the most important research subjects in modern manufacturing. However, the research on lightweight of shell models is rare, and most limited in topological changes. This article proposes a local heat sensor–based lightweight framework of shell models that consists of model analysis, lightweight modeling and analysis, and three-dimensional printing and practical validation in an optimum iterative procedure. Specifically, first, both geometric features and empirical features are introduced to construct a frame structure. Second, a local diffusion–based heat sensor network is exploited to simulate the stress distribution due to two reasons: one is that they have the similar physical transmissibility and the other is that the heat diffusion is smooth, and it guarantees that the thickness variation is smooth and natural without restriction on the degrees of freedom. Then, a local iteration consists of heat simulation and stress analysis is utilized to further improve the efficiency. Finally, we use three-dimensional printer to manufacture testing models and apply them to practical verification and feedback. Our extensive experiments have exhibited many attractive properties, including the flexibility and freedom of the thickness variation, the effectiveness, and credibility of the lightweight.

scholarly journals Dynamic Response Analysis of an Asymmetric Coupled Vehicle-Track System Generated by Voided Elastic Two-Block Sleeper

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Zhenxing He ◽  
Xinwen Yang
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Dynamic Responses ◽  
Response Analysis ◽  
Creep Theory ◽  
Coupling Vibration ◽  
Running Safety ◽  
Car Body ◽  
Track System ◽  
Nonlinear Elastic

Based on vehicle-track coupled dynamic theory, a three-dimensional asymmetric vehicle-track coupling vibration model is developed to investigate the effect of voided elastic two-block sleepers on vehicle and track system dynamic responses. For the vehicle system, one car body, two frames, and four wheel sets are assumed to be rigid, with 35 degrees of freedom (DOF). For the track system, the rails and the concrete two-block sleepers are the main vibration components. The rails are modelled as Timoshenko beams, and the concrete two-block sleepers are assumed to be rigid mass with vertical and lateral movement. The pads under the rails and the rubber boots under the sleepers provide greater vertical and lateral elasticity for the track. The Hertz nonlinear elastic contact theory is used to calculate the normal wheel/rail force. The wheel/rail tangent creep force is first calculated using Kalker’s linear creep theory and then modified by the Shen-Hedrick-Elkins theory. The results show that the asymmetric voided elastic two-block sleepers have greater effects on the dynamic responses for fasteners and sleepers than on the car body and the wheel/rail forces under measured geometric irregularity and random irregularity. Two or more voided sleepers will greatly affect the vehicle running safety.

Macroorganisation and flexibility of thylakoid membranes

2019 ◽  
Vol 476 (20) ◽  
pp. 2981-3018 ◽  
Author(s):  
Petar H. Lambrev ◽  
Parveen Akhtar
Keyword(s):  
Light Harvesting ◽  
Current Knowledge ◽  
Three Dimensional ◽  
Photosynthetic Apparatus ◽  
Dynamic Responses ◽  
State Transitions ◽  
Photochemical Quenching ◽  
Light Harvesting Complex ◽  
Complex Ii ◽  
Light Harvesting Complex Ii

Abstract The light reactions of photosynthesis are hosted and regulated by the chloroplast thylakoid membrane (TM) — the central structural component of the photosynthetic apparatus of plants and algae. The two-dimensional and three-dimensional arrangement of the lipid–protein assemblies, aka macroorganisation, and its dynamic responses to the fluctuating physiological environment, aka flexibility, are the subject of this review. An emphasis is given on the information obtainable by spectroscopic approaches, especially circular dichroism (CD). We briefly summarise the current knowledge of the composition and three-dimensional architecture of the granal TMs in plants and the supramolecular organisation of Photosystem II and light-harvesting complex II therein. We next acquaint the non-specialist reader with the fundamentals of CD spectroscopy, recent advances such as anisotropic CD, and applications for studying the structure and macroorganisation of photosynthetic complexes and membranes. Special attention is given to the structural and functional flexibility of light-harvesting complex II in vitro as revealed by CD and fluorescence spectroscopy. We give an account of the dynamic changes in membrane macroorganisation associated with the light-adaptation of the photosynthetic apparatus and the regulation of the excitation energy flow by state transitions and non-photochemical quenching.

scholarly journals Design, Fabrication, and Testing of a Novel 3D 3-Fingered Electrothermal Microgripper with Multiple Degrees of Freedom

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 444
Author(s):  
Guoning Si ◽  
Liangying Sun ◽  
Zhuo Zhang ◽  
Xuping Zhang
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Polyimide Film ◽  
Zebrafish Embryos ◽  
Multiple Degrees Of Freedom ◽  
Electrothermal Actuator ◽  
3D Space ◽  
Pick And Place

This paper presents the design, fabrication, and testing of a novel three-dimensional (3D) three-fingered electrothermal microgripper with multiple degrees of freedom (multi DOFs). Each finger of the microgripper is composed of a V-shaped electrothermal actuator providing one DOF, and a 3D U-shaped electrothermal actuator offering two DOFs in the plane perpendicular to the movement of the V-shaped actuator. As a result, each finger possesses 3D mobilities with three DOFs. Each beam of the actuators is heated externally with the polyimide film. The durability of the polyimide film is tested under different voltages. The static and dynamic properties of the finger are also tested. Experiments show that not only can the microgripper pick and place microobjects, such as micro balls and even highly deformable zebrafish embryos, but can also rotate them in 3D space.

scholarly journals Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098705
Author(s):  
Xinran Wang ◽  
Yangli Zhu ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xuehui Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Element Model ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Response ◽  
Rotating Speed ◽  
Torque Load ◽  
Set Up ◽  
Two Stages

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

Effects of Dynamic Model Errors in Task-Priority Operational Space Control

Robotica ◽  
2021 ◽  
pp. 1-12
Author(s):  
Paolo Di Lillo ◽  
Gianluca Antonelli ◽  
Ciro Natale
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Inverse Dynamics ◽  
Null Space ◽  
Control Algorithms ◽  
Model Errors ◽  
Operational Space ◽  
Dynamic Level ◽  
Concurrent Tasks ◽  
Modeling Errors

SUMMARY Control algorithms of many Degrees-of-Freedom (DOFs) systems based on Inverse Kinematics (IK) or Inverse Dynamics (ID) approaches are two well-known topics of research in robotics. The large number of DOFs allows the design of many concurrent tasks arranged in priorities, that can be solved either at kinematic or dynamic level. This paper investigates the effects of modeling errors in operational space control algorithms with respect to uncertainties affecting knowledge of the dynamic parameters. The effects on the null-space projections and the sources of steady-state errors are investigated. Numerical simulations with on-purpose injected errors are used to validate the thoughts.

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