Limitations of a dynamic shear-frame model based in a small-scale experimental steel structure

Many engineering problems require geometric modeling and mechanical simulation of structures. Through the structural models, engineers try to simulate the real behavior of these structures. It is important that a model contain all the necessary parameters that describe the structure and its behavior during its useful life. In the field of dynamics, one of the most used models is the shear-frame, in which the stiffness of the structure is given by the stiffness of the columns and the whole mass is concentrated in the floor levels, which are considered with infinite stiffness. In some cases, this simplification offers more conservative results, which can lead to considerable errors, especially in the case of natural frequencies. Knowing that the quality of a structural model depends on the simplifications considered, an experimental 3D steel frame, constructed to typify the dynamic behavior of a tall building, was tested with a data acquisition system and accelerometers, in order to obtain its natural frequencies. In addition, a numerical model was developed in order to ascertain the results. These values of natural frequencies are compared with an idealized shear-frame model obtained from the experimental model. This comparison allows a critical analysis of the numerical models that can be employed to represent the real dynamic behavior of structures. The aim of the investigation is to show the results of the modal analysis for each model, comparing them with the experimental results and commenting their advantages and the limitations.

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Presentation and discussion of the high-resolution atmosphere–land-surface–subsurface simulation dataset of the simulated Neckar catchment for the period 2007–2015

Earth System Science Data ◽

10.5194/essd-13-4437-2021 ◽

2021 ◽

Vol 13 (9) ◽

pp. 4437-4464

Author(s):

Bernd Schalge ◽

Gabriele Baroni ◽

Barbara Haese ◽

Daniel Erdal ◽

Gernot Geppert ◽

...

Keyword(s):

High Resolution ◽

Land Surface ◽

Overland Flow ◽

Water Cycle ◽

Numerical Models ◽

Model Performance ◽

Small Scale ◽

The Real ◽

Community Land Model ◽

Terrestrial System

Abstract. Coupled numerical models, which simulate water and energy fluxes in the subsurface–land-surface–atmosphere system in a physically consistent way, are a prerequisite for the analysis and a better understanding of heat and matter exchange fluxes at compartmental boundaries and interdependencies of states across these boundaries. Complete state evolutions generated by such models may be regarded as a proxy of the real world, provided they are run at sufficiently high resolution and incorporate the most important processes. Such a simulated reality can be used to test hypotheses on the functioning of the coupled terrestrial system. Coupled simulation systems, however, face severe problems caused by the vastly different scales of the processes acting in and between the compartments of the terrestrial system, which also hinders comprehensive tests of their realism. We used the Terrestrial Systems Modeling Platform (TerrSysMP), which couples the meteorological Consortium for Small-scale Modeling (COSMO) model, the land-surface Community Land Model (CLM), and the subsurface ParFlow model, to generate a simulated catchment for a regional terrestrial system mimicking the Neckar catchment in southwest Germany, the virtual Neckar catchment. Simulations for this catchment are made for the period 2007–2015 and at a spatial resolution of 400 m for the land surface and subsurface and 1.1 km for the atmosphere. Among a discussion of modeling challenges, the model performance is evaluated based on observations covering several variables of the water cycle. We find that the simulated catchment behaves in many aspects quite close to observations of the real Neckar catchment, e.g., concerning atmospheric boundary-layer height, precipitation, and runoff. But also discrepancies become apparent, both in the ability of the model to correctly simulate some processes which still need improvement, such as overland flow, and in the realism of some observation operators like the satellite-based soil moisture sensors. The whole raw dataset is available for interested users. The dataset described here is available via the CERA database (Schalge et al., 2020): https://doi.org/10.26050/WDCC/Neckar_VCS_v1.

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THE CALCULATION AND MEASUREMENT OF THE NATURAL FREQUENCIES OF THE BUCKET WHEEL EXCAVATOR SCHRS 1320/4X30

Transport ◽

10.3846/transport.2010.33 ◽

2010 ◽

Vol 25 (3) ◽

pp. 269-277 ◽

Cited By ~ 18

Author(s):

Jakub Gottvald

Keyword(s):

Numerical Simulation ◽

Numerical Simulations ◽

Dynamic Load ◽

Natural Frequencies ◽

Numerical Models ◽

Dynamic Properties ◽

Experimental Measurements ◽

The Real ◽

Comparison Of Results

Natural frequencies and shapes are the basic dynamic properties of each structure. On the basis of their knowledge, the sensitivity of the structure to a dynamic load could be estimated. While designing, natural frequencies are based on calculations and numerical simulations. However, computational numerical models do not exactly correspond with real structures and there are many details which have to be simplified. It means that the real natural frequencies of structures may differ from the calculated ones. It is advantageous to verify the calculated results by suitable experimental measurements in case of structures where a dynamic load dominates. The paper deals with the experimental measuring of the natural frequencies of the bucket wheel excavator SchRs 1320/4x30 and a comparison of results obtained from experimental measurements and detailed numerical simulation applying ANSYS.

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Influence of Multiphysical Effects on the Dynamics of the High Speed Mini Rotors—Part II: Results

Journal of Vibration and Acoustics ◽

10.1115/1.4000788 ◽

2010 ◽

Vol 132 (3) ◽

Cited By ~ 3

Author(s):

Emre Dikmen ◽

Peter J. M. van der Hoogt ◽

André de Boer ◽

Ronald G. K. M. Aarts

Keyword(s):

Modal Analysis ◽

Dynamic Behavior ◽

High Speed ◽

Structural Model ◽

Natural Frequencies ◽

Experimental Setup ◽

Flexible Supports ◽

The Stability ◽

Surrounding Fluid ◽

Theoretical Results

In Part I of this work, a theoretical analysis showed that the surrounding air in the closed confinement between rotor and casing has a significant effect on the dynamic behavior of high speed minirotors. In order to validate the developed theoretical model, an experimental setup is designed and the dynamic behavior of the rotor with medium gap confinement is studied. The experimental setup has flexible supports, which consist of beams with adjustable length. The support stiffness is changed by altering the beam length. Modal analysis of the rotor is done in free-free conditions in order to test the capability of the rotordynamic model without the supports and multiphysical effects. The experimental and simulation results agree well with a difference of 1%. Then modal analysis of the whole structure is done at standstill and during operation in the absence of the casing. In this way, multiphysical effects are eliminated and only support effects on the dynamics of the structure are observed. The supports appear to have significant effect on the natural frequencies of the flexural modes of the system. Different support modeling techniques are studied and adequate equivalent models are obtained. These models are then implemented into the structural model of the rotor. Finally, multiphysical effects are tested at different speeds with different support stiffnesses. Experiments are performed with and without the casing for determining the change in the natural frequencies and onset of instability. The surrounding fluid has a significant effect on the stability of the system while the natural frequencies do not change significantly. The experimental and theoretical results are in fair agreement for predicting the natural frequencies and the onset of instability.

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EVALUASI PENGUJIAN VIBRASI STRUKTUR (STUDI KASUS : DERMAGA DONGGALA)

Jurnal Muara Sains, Teknologi, Kedokteran dan Ilmu Kesehatan ◽

10.24912/jmstkik.v3i1.2730 ◽

2019 ◽

Vol 3 (1) ◽

pp. 71

Author(s):

Devlin Tedy ◽

Wiryanto Dewobroto

Keyword(s):

Numerical Analysis ◽

Numerical Model ◽

Natural Frequency ◽

Dynamic Behavior ◽

Structural Model ◽

Natural Frequencies ◽

Vibration Test ◽

Test Results ◽

Vibration Testing ◽

Accelerometer Sensor

Setiap struktur memiliki perilaku dinamik berupa frekuensi alami yang dapat dicari dengan uji vibrasi di lapangan secara empiris dan analisis numerik. Frekuensi alami terdiri dari massa, kekakuan, dan arah (mode shape). Parameter-parameter tersebut menghasilkan banyak variasi model struktur. Model yang paling tepat dengan kondisi lapangan dapat dicari dengan bantuan hasil uji vibrasi yang berfungsi sebagai kalibrator. Dalam mencari frekuensi alami melalui uji vibrasi sangat tergantung pada teknologi seperti tipe sensor dan cara penempatannya yang digunakan untuk merekam getaran yang diberikan. Tipe sensor terdiri dari berbagai macam seperti uniaxial, biaxial, dan triaxial. Pada kasus uji vibrasi struktur dermaga Donggala menggunakan 6 buah sensor accelerometer uniaxial. Sensor dipasang dalam 3 tempat berbeda masing-masing tempat dalam arah lateral dan vertikal. Hasil pengujian dari pihak surveyor didalam mengevaluasi hasilnya hanya rata-rata tanpa memperhitungkan pengaruh arah. Hal ini yang akan dievaluasi pada penelitian ini. Evaluasi yang akan dilakukan adalah membandingkan hasil pengujian vibrasi dengan analisis numerik. Dari berbagai model analisis numerik dapat diketahui bahwa meskipun nilai frekuensi alaminya bervariasi tetapi masih didalam batas nilai tertentu. Dengan melihat apakah arah penempatan sensor dan arah tumbukan kapal, maka dapat diprediksi perilaku dinamik dermaga apakah translasi atau rotasi yang terjadi. Dengan demikian evaluasi yang digunakan oleh surveyor dengan melakukan rata-rata tanpa melihat arah adalah tidak tepat. Oleh sebab itu akan dilakukan evaluasi ulang mempelajari arah pemberian gaya, arah pemasangan dan penempatan sensor accelerometer serta perlu melakukan pengelompokan hasil pengujian vibrasi berdasarkan arah sensor. Setelah mempelajari model numerik dari dermaga dapat diketahui bahwa model numerik yang bertranslasi mempunyai kesesuaian dengan data tumbukan pada salah satu titik sensor yang dipasang. Pemodelan numerik yang mendekati nilai ini adalah sesuai dengan data perencanaan sebelumnya. Dari penelitian ini dapat diketahui bahwa pemahaman pengujian vibrasi perlu dilakukan pengelompokan sesuai arah penempatan sensor dan tidak dapat dilakukan rata-rata. Each structure has dynamic behavior in the form of natural frequencies that can be searched by vibration testing in the field empirically and numerical analysis. Natural frequency consists of mass, stiffness, and direction (shape mode). These parameters produce many variations of the structural model. The most appropriate model with field conditions can be sought with the help of vibration test results that function as a calibrator. In searching for natural frequencies through vibration testing it is very dependent on technology such as the type of sensor and the way it is used to record the vibrations given. Sensor types consist of various types such as uniaxial, biaxial, and triaxial. In the case of vibration test the Donggala pier structure uses 6 uniaxial accelerometer sensors. Sensors are installed in 3 different places each in lateral and vertical directions. Test results from the surveyor in evaluating the results are only average without taking into account the influence of direction. This will be evaluated in this study. The evaluation will be done is to compare the results of vibration testing with numerical analysis. From various numerical analysis models, it can be seen that although the natural frequency values vary, they are still within certain limits. By looking at the direction of the placement of the sensor and the direction of the collision of the ship, it can be predicted the dynamic behavior of the pier whether translation or rotation is happening. Thus the evaluation used by the surveyors by averaging without looking at directions is incorrect. Therefore a re-evaluation will be conducted to study the direction of the force, the direction of the placement and placement of the accelerometer sensor and the need to group the results of vibration testing based on the sensor direction. After studying the numerical model from the dock, it can be seen that the numerical model that translates has conformity to the collision data at one of the installed sensor points. Numerical modeling which is close to this value is in accordance with previous planning data. From this research it can be seen that the understanding of vibration testing needs to be grouped according to the direction of the sensor placement and cannot be carried out on average.

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Numerical and Experimental Dynamic Analysis of IC Engine Test Beds Equipped with Highly Flexible Couplings

Shock and Vibration ◽

10.1155/2017/5802702 ◽

2017 ◽

Vol 2017 ◽

pp. 1-16 ◽

Cited By ~ 1

Author(s):

M. Cocconcelli ◽

M. Troncossi ◽

E. Mucchi ◽

A. Agazzi ◽

A. Rivola ◽

...

Keyword(s):

Dynamic Behavior ◽

Optical Sensors ◽

Torsional Vibration ◽

Internal Combustion Engines ◽

Natural Frequencies ◽

Numerical Models ◽

Engine Test ◽

Test Rig ◽

Ic Engine ◽

Premature Failure

Driveline components connected to internal combustion engines can be critically loaded by dynamic forces due to motion irregularity. In particular, flexible couplings used in engine test rig are usually subjected to high levels of torsional oscillations and time-varying torque. This could lead to premature failure of the test rig. In this work an effective methodology for the estimation of the dynamic behavior of highly flexible couplings in real operational conditions is presented in order to prevent unwanted halts. The methodology addresses a combination of numerical models and experimental measurements. In particular, two mathematical models of the engine test rig were developed: a torsional lumped-parameter model for the estimation of the torsional dynamic behavior in operative conditions and a finite element model for the estimation of the natural frequencies of the coupling. The experimental campaign addressed torsional vibration measurements in order to characterize the driveline dynamic behavior as well as validate the models. The measurements were achieved by a coder-based technique using optical sensors and zebra tapes. Eventually, the validated models were used to evaluate the effect of design modifications of the coupling elements in terms of natural frequencies (torsional and bending), torsional vibration amplitude, and power loss in the couplings.

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Experimental Modal Test of the Laboratory Model of Steel Truss Structure

Civil and Environmental Engineering ◽

10.1515/cee-2016-0016 ◽

2016 ◽

Vol 12 (2) ◽

pp. 116-121 ◽

Cited By ~ 4

Author(s):

Ján Kortiš ◽

Ľuboš Daniel ◽

Milan Škarupa ◽

Maroš Ďuratný

Keyword(s):

Natural Frequencies ◽

Numerical Models ◽

Steel Structure ◽

Modal Testing ◽

Mode Shapes ◽

Laboratory Model ◽

Residual Lifetime ◽

Good Tool ◽

Modal Test ◽

Proper Estimation

Abstract The experimental modal analysis is often used to validate the accuracy of dynamic numerical models. It is also a good tool to obtain valuable information about current condition of the structures that could help to determine residual lifetime. The quality of modal testing results is highly dependent on the proper estimation of the natural frequencies from the frequency response function. This article presents the experimental modal test of the laboratory steel structure in which the natural frequencies and mode shapes are determined.

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Stochastic simulation of the spatio-temporal field of the average daily heat index in Southern Russia

Climate Research ◽

10.3354/cr01623 ◽

2020 ◽

Vol 82 ◽

pp. 149-160

Author(s):

N Kargapolova

Keyword(s):

Heat Waves ◽

Numerical Models ◽

Heat Index ◽

Real Field ◽

Gaussian Field ◽

The Real ◽

Southern Russia ◽

Weather Stations ◽

Spatio Temporal ◽

Temporal Field

Numerical models of the heat index time series and spatio-temporal fields can be used for a variety of purposes, from the study of the dynamics of heat waves to projections of the influence of future climate on humans. To conduct these studies one must have efficient numerical models that successfully reproduce key features of the real weather processes. In this study, 2 numerical stochastic models of the spatio-temporal non-Gaussian field of the average daily heat index (ADHI) are considered. The field is simulated on an irregular grid determined by the location of weather stations. The first model is based on the method of the inverse distribution function. The second model is constructed using the normalization method. Real data collected at weather stations located in southern Russia are used to both determine the input parameters and to verify the proposed models. It is shown that the first model reproduces the properties of the real field of the ADHI more precisely compared to the second one, but the numerical implementation of the first model is significantly more time consuming. In the future, it is intended to transform the models presented to a numerical model of the conditional spatio-temporal field of the ADHI defined on a dense spatio-temporal grid and to use the model constructed for the stochastic forecasting of the heat index.

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Dynamic analysis of a helical gear reduction by experimental and numerical methods

Noise Control Engineering Journal ◽

10.3397/1/37684 ◽

2020 ◽

Vol 68 (1) ◽

pp. 48-58

Author(s):

Chao Liu ◽

Zongde Fang ◽

Fang Guo ◽

Long Xiang ◽

Yabin Guan ◽

...

Keyword(s):

Numerical Methods ◽

Dynamic Analysis ◽

Dynamic Behavior ◽

Fourth Order ◽

Numerical Models ◽

Helical Gear ◽

Operating Conditions ◽

Dynamic Responses ◽

Lumped Mass ◽

Gear Mesh

Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.

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The Effectiveness of Ensemble-Neural Network Techniques to Predict Peak Uplift Resistance of Buried Pipes in Reinforced Sand

Applied Sciences ◽

10.3390/app11030908 ◽

2021 ◽

Vol 11 (3) ◽

pp. 908

Author(s):

Jie Zeng ◽

Panagiotis G. Asteris ◽

Anna P. Mamou ◽

Ahmed Salih Mohammed ◽

Emmanuil A. Golias ◽

...

Keyword(s):

Neural Network ◽

Numerical Models ◽

Correlation Coefficients ◽

Network Models ◽

Small Scale ◽

Offshore Platforms ◽

Neural Network Models ◽

Buried Pipes ◽

Ensemble Techniques ◽

Uplift Resistance

Buried pipes are extensively used for oil transportation from offshore platforms. Under unfavorable loading combinations, the pipe’s uplift resistance may be exceeded, which may result in excessive deformations and significant disruptions. This paper presents findings from a series of small-scale tests performed on pipes buried in geogrid-reinforced sands, with the measured peak uplift resistance being used to calibrate advanced numerical models employing neural networks. Multilayer perceptron (MLP) and Radial Basis Function (RBF) primary structure types have been used to train two neural network models, which were then further developed using bagging and boosting ensemble techniques. Correlation coefficients in excess of 0.954 between the measured and predicted peak uplift resistance have been achieved. The results show that the design of pipelines can be significantly improved using the proposed novel, reliable and robust soft computing models.

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Observational aspects of prominence oscillations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308014816 ◽

2007 ◽

Vol 3 (S247) ◽

pp. 152-157 ◽

Cited By ~ 4

Author(s):

Oddbjørn Engvold

Keyword(s):

Magnetic Structure ◽

Numerical Models ◽

Small Scale ◽

Solar Prominences ◽

Scale Structures ◽

Oscillations And Waves ◽

Available Information ◽

Small Scale Structures

AbstractSeismology has become a powerful tool in studies of the magnetic structure of solar prominences and filaments. Reversely, analytical and numerical models are guided by available information about the spatial and thermodynamical structure of these enigmatic structures. The present invited paper reviews recent observational results on oscillations and waves as well as details about small-scale structures and dynamics of prominences and filaments.

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