On the Uniqueness of Solutions for the Identification of Linear Structural Systems

2005 ◽  
Vol 73 (1) ◽  
pp. 153-162 ◽  
Author(s):  
Guillermo Franco ◽  
Raimondo Betti ◽  
Richard W. Longman
Keyword(s):  
Prior Knowledge ◽  
Degrees Of Freedom ◽  
Identification Problem ◽  
Minimum Amount ◽  
Structural Systems ◽  
Structural System ◽  
Uniqueness Of Solutions ◽  
Stiffness Identification ◽  
Shear Type ◽  
Forced Excitation

This work tackles the problem of global identifiability of an undamped, shear-type, N degrees of freedom linear structural system under forced excitation without any prior knowledge of its mass or stiffness distributions. Three actuator/sensor schemes are presented, which guarantee the existence of only one solution for the mass and stiffness identification problem while requiring a minimum amount of instrumentation (only 1 actuator and 1 or 2 sensors). Through a counterexample for a 3DOF system it is also shown that fewer measurements than those suggested result invariably in non-unique solutions.

Uniqueness of Solutions for the Identification of Linear Reduced Order Structural Systems

2004 ◽  
Author(s):  
Guillermo Franco ◽  
Jun Yu ◽  
Raimondo Betti
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Technique ◽  
Identification Problem ◽  
Structural Systems ◽  
Uniqueness Of Solutions ◽  
Reduced Order ◽  
Theoretical Approaches ◽  
Uniqueness Of The Solution ◽  
Minimum Number ◽  
Output Information

The problem of identification of structural systems is an inverse problem that uses input (say force excitation) and output information (accelerations, for instance) to obtain an optimal model to describe the system’s behavior. Since a full instrumentation setup is expensive, situations usually arise where only partial measurements are available. Uniqueness of the solution in these circumstances might not be guaranteed. This paper analyzes the minimum number of measurements required to ensure that only one solution exists for the identification problem of mass, damping and stiffness distributions of shear-type N degrees of freedom linear structures. Three typical configurations of measurements are studied with two distinct theoretical approaches, one based on classical polynomial theory, the other based on reduced order model theory. Both these approaches lead to the conclusion that only one input and one or two output measurements are sufficient to guarantee uniqueness of identification, depending on the selected location of the input measurement. Additionally, the identification of a 3DOF system is carried out analytically with the usage of Sylvester’s Dyalitic Elimination to show that fewer measurements than the ones proposed lead to non-unique identification. This fact is also illustrated with the usage of a recently developed optimization technique, with which convergence to the different solutions is observed depending on the initial estimate used.

Dynamic Condensation and Synthesis of Unsymmetric Structural Systems

2002 ◽  
Vol 69 (5) ◽  
pp. 610-616 ◽  
Author(s):  
G. Visweswara Rao
Keyword(s):  
Model Reduction ◽  
Degrees Of Freedom ◽  
Structural Systems ◽  
Structural System ◽  
Lanczos Algorithm ◽  
Order Model ◽  
Reduction Procedure ◽  
Reduced Order ◽  
Large Size ◽  
Dynamic Condensation

In this paper model reduction of an unsymmetric and damped structural system is presented using a two-sided dynamic condensation technique. The method is an iterative one and essentially utilizes orthonormalized complex eigenvectors of the unsymmetric system. The eigensolution of the reduced order model with specified master degrees-of-freedom is obtained by Lanczos algorithm. The model reduction procedure is further utilized in substructure synthesis and eigenvalue analysis of large size unsymmetric systems. Application of the condensation technique is illustrated via two example problems of rotor bearing systems.

scholarly journals Identification of time-varying systems with partial acceleration measurements by synthesis of wavelet decomposition and Kalman filter

2020 ◽  
Vol 12 (6) ◽  
pp. 168781402093046
Author(s):  
Siyi Chen ◽  
Jubin Lu ◽  
Ying Lei
Keyword(s):  
Kalman Filter ◽  
Degrees Of Freedom ◽  
Structural Parameters ◽  
Parametric Identification ◽  
Identification Problem ◽  
Structural Systems ◽  
Wavelet Expansion ◽  
Time Varying ◽  
Multiresolution Decomposition ◽  
Original Time

Structural systems often exhibit time-varying dynamic characteristics during their service life due to serve hazards and environmental erosion, so the identification of time-varying structural systems is an important research topic. Among the previous methodologies, wavelet multiresolution analysis for time-varying structural systems has gained increasing attention in the past decades. However, most of the existing wavelet-based identification approaches request the full measurements of structural responses including acceleration, velocity, and displacement responses at all dynamic degrees of freedom. In this article, an improved algorithm is proposed for the identification of time-varying structural parameters using only partial measurements of structural acceleration responses. The proposed algorithm is based on the synthesis of wavelet multiresolution decomposition and the Kalman filter approach. The time-varying structural stiffness and damping parameters are expanded at multi-scale profile by wavelet multiresolution decomposition, so the time-varying parametric identification problem is converted into a time-invariant one. Structural full responses are estimated by Kalman filter using partial observations of structural acceleration responses. The scale coefficients by the wavelet expansion are estimated via the solution of a nonlinear optimization problem of minimizing the errors between estimated and observed accelerations. Finally, the original time-varying parameters can be reconstructed. To demonstrate the efficiency of the proposed algorithm, the identification of several numerical examples with various time-varying scenarios is studied.

COMPREHENSIVE REFORMING OF TECHNOLOGICAL, FUNCTIONAL AND STRUCTURAL SYSTEMS OF SKIN UNITS OF HOSPITALS

2020 ◽  
pp. 211-218
Author(s):  
Владимир Григорьевич Донцов ◽  
Елена Владимировна Донцова ◽  
Любовь Анатольевна Новикова ◽  
Лариса Николаевна Борзунова
Keyword(s):  
Service System ◽  
Medical Examination ◽  
Structural Systems ◽  
Structural System ◽  
Structural Units

В статье доказана порочность переустройства только одной структурной системы (реструктуризации), так как это чревато поломками элементов, звеньев и блоков, сомой системы кожной службы. Допустимо лишь незначительная адаптация к конкретным условиям больниц, где это будет внедряться. Сформулированы понятия конечного результата работы врачей и структурных подразделений медицинских стационаров в современных условиях общественно-политической формации. Описаны преимущества реконструкции комплекса систем судебно-медицинской экспертизы как экспериментальной службы для кожного отделения городской многопрофильной больницы и работы самого кожного отделения. Описана форма структурного построения судебно-медицинской и кожной служб. По аналоги с экспертным учреждением ожидаются аналогичные изменение конечного результата в кожном подразделении многопрофильного стационара The article proves the viciousness of the reorganization of only one structural system (restructuring), since this is fraught with breakdowns of elements, links and blocks, the soma of the skin service system. Only slight adaptation to the specific conditions of the hospitals where it will be implemented is acceptable. The concepts of the final result of the work of doctors and structural units of medical hospitals in the modern conditions of the socio-political formation are formulated. The advantages of reconstruction of a complex of forensic medical examination systems as an experimental service for the skin department of a city multidisciplinary hospital and the work of the skin department itself are described. The form of structural structure of forensic and skin services is described. By analogy with an expert institution, a similar change in the final result is expected in the skin department of a multidisciplinary hospital

scholarly journals Parametric Analysis of the Shear Lag Effect in Tube Structural Systems of Tall Buildings

2020 ◽  
Vol 11 (1) ◽  
pp. 278
Author(s):  
Ivan Hafner ◽  
Anđelko Vlašić ◽  
Tomislav Kišiček ◽  
Tvrtko Renić
Keyword(s):  
Parametric Analysis ◽  
Numerical Models ◽  
Tall Buildings ◽  
Structural Systems ◽  
Structural Elements ◽  
Structural System ◽  
Shear Lag ◽  
Shear Lag Effect ◽  
Lag Effect ◽  
Secondary Structural Elements

Horizontal loads such as earthquake and wind are considered dominant loads for the design of tall buildings. One of the most efficient structural systems in this regard is the tube structural system. Even though such systems have a high resistance when it comes to horizontal loads, the shear lag effect that is characterized by an incomplete and uneven activation of vertical elements may cause a series of problems such as the deformation of internal panels and secondary structural elements, which cumulatively grow with the height of the building. In this paper, the shear lag effect in a typical tube structure will be observed and analyzed on a series of different numerical models. A parametric analysis will be conducted with a great number of variations in the structural elements and building layout, for the purpose of giving recommendations for an optimal design of a tube structural system.

scholarly journals Wavelet multi-resolution approximation of time-varying frame structure

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879559 ◽  
Author(s):  
Min Xiang ◽  
Feng Xiong ◽  
Yuanfeng Shi ◽  
Kaoshan Dai ◽  
Zhibin Ding
Keyword(s):  
Parameter Estimation ◽  
Degrees Of Freedom ◽  
Structural Parameters ◽  
Identification Problem ◽  
Frame Structure ◽  
Structural Parameter ◽  
Time Varying ◽  
Engineering Structures ◽  
Time Frequency ◽  
Non Parametric

Engineering structures usually exhibit time-varying behavior when subjected to strong excitation or due to material deterioration. This behavior is one of the key properties affecting the structural performance. Hence, reasonable description and timely tracking of time-varying characteristics of engineering structures are necessary for their safety assessment and life-cycle management. Due to its powerful ability of approximating functions in the time–frequency domain, wavelet multi-resolution approximation has been widely applied in the field of parameter estimation. Considering that the damage levels of beams and columns are usually different, identification of time-varying structural parameters of frame structure under seismic excitation using wavelet multi-resolution approximation is studied in this article. A time-varying dynamical model including both the translational and rotational degrees of freedom is established so as to estimate the stiffness coefficients of beams and columns separately. By decomposing each time-varying structural parameter using one wavelet multi-resolution approximation, the time-varying parametric identification problem is transformed into a time-invariant non-parametric one. In solving the high number of regressors in the non-parametric regression program, the modified orthogonal forward regression algorithm is proposed for significant term selection and parameter estimation. This work is demonstrated through numerical examples which consider both gradual variation and abrupt changes in the structural parameters.

Damage Identification in Collocated Structural Systems Using Structural Markov Parameters

2013 ◽  
Author(s):  
Ramin Bighamian ◽  
Hamid Reza Mirdamadi ◽  
Jin-Oh Hahn
Keyword(s):  
Structural Damage ◽  
Damage Identification ◽  
Mode Shapes ◽  
Structural Systems ◽  
Structural System ◽  
Computationally Efficient ◽  
Markov Parameters ◽  
Novel Approach ◽  
Stiffness Matrices ◽  
Stiffness Characteristics

This paper presents a novel approach to damage identification in a class of collocated multi-input multi-output structural systems. In the proposed approach, damage is identified via the structural Markov parameters obtained from a system identification procedure, which is in turn exploited to localize and quantify damage by evaluating relative changes occurring in the mass and stiffness matrices associated with the structural system. To this aim, an explicit relationship between structural Markov parameters versus mass and stiffness matrices is developed. The main strengths of the proposed approach are that it is capable of quantitatively identifying the occurrence of multiple damages associated with both mass and stiffness characteristics in the structural system, and it is computationally efficient in that it is solely based on the structural Markov parameters but does not necessitate costly calculations related to natural frequencies and mode shapes, making it highly attractive for structural damage detection and health monitoring applications. Numerical examples are provided to demonstrate the validity and effectiveness of the proposed approach.

scholarly journals Methodology to Evaluate the Embodied Primary Energy and CO2 Production at Each Stage of the Life Cycle of Prefabricated Structural Systems: The Case of the Solar Decathlon Competition

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4311
Author(s):  
J.F. Luna-Tintos ◽  
Carlos Cobreros ◽  
Álvaro López-Escamilla ◽  
Rafael Herrera-Limones ◽  
Miguel Torres-García
Keyword(s):  
Life Cycle ◽  
Construction Industry ◽  
Primary Energy ◽  
Co2 Production ◽  
Structural Systems ◽  
Structural System ◽  
Audit Tool ◽  
Solar Decathlon ◽  
Environmental Demand ◽  
Emission Of Greenhouse Gases

The construction industry is responsible for a high percentage of the energy consumed on the planet and the emission of greenhouse gases, therefore it is considered necessary to rethink many of the processes that this industry carries out in order to reduce its environmental impact. For this, one of the paths could take into account the Life Cycle Assessment of the used materials, for which it is necessary to evaluate this aspect through indicators that allow the qualification and quantification of the weight of these environmental impacts. In this context, this article presents a methodological proposal for the quantitative evaluation of the embodied primary energy and CO2 production at each stage of the life cycle of prefabricated structural systems, taking as case studies eight prototypes from the “Solar Decathlon” competition in its editions of Europe (2014), United States (2015) and Latin America (2015), through a Simplified Life Cycle Analysis, using the Eco Audit tool from CES Edupack. Through this analysis, conclusions are drawn about the optimization of a structural system with lower environmental demand and the possibilities of transferring knowledge from this competition to be applied in innovative systems of new housing models.

Approach to Steel-Bamboo Composite Structure System

2013 ◽  
Vol 300-301 ◽  
pp. 1263-1266 ◽  
Author(s):  
Zhi Min Yan ◽  
Yong Fei Du ◽  
Jun Guo Huang ◽  
Yu Shun Li
Keyword(s):  
Energy Saving ◽  
High Strength ◽  
Structural Systems ◽  
Structural Elements ◽  
Structural System ◽  
Sustainable Building ◽  
Production Methods ◽  
Building Technology ◽  
Earthquake Resistant ◽  
New Type

Modern bamboo structural system is a new type of green sustainable building technology, conform with our country’s requirements of developing environment-protecting and energy-saving buildings. This paper presents a new lightweight, high-strength , earthquake-resistant and energy-saving system-steel-bamboo composite structural systems , and given the various structural elements of the composite structural systems of steel-bamboo production methods . This paper also gives the production methods of steel-bamboo composite elements. Steel-bamboo-structural system can per-fectly combine steel and bamboo to bear load together, and it have excellent mechanical properties and broad application prospects.

scholarly journals QUANTUM ESTIMATION OF RELATIVE INFORMATION

2006 ◽  
Vol 04 (01) ◽  
pp. 131-149 ◽  
Author(s):  
NETANEL H. LINDNER ◽  
PETRA F. SCUDO ◽  
DAGMAR BRUß
Keyword(s):  
Symmetry Group ◽  
Prior Knowledge ◽  
Reference Frame ◽  
Spatial Orientation ◽  
Degrees Of Freedom ◽  
Estimation Procedure ◽  
Quantum Systems ◽  
Relative Information ◽  
Rotation Parameters ◽  
Require Information

We derive optimal schemes for preparation and estimation of relational degrees of freedom between two quantum systems. We specifically analyze the case of rotation parameters representing relative angles between elements of the SU(2) symmetry group. Our estimation procedure does not assume prior knowledge of the absolute spatial orientation of the systems and as such does not require information on the underlying classical reference frame in which the states are prepared.

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