scholarly journals Structural Pounding Detection by Using Wavelet Scalogram

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Shutao Xing ◽  
Marvin W. Halling ◽  
Qingli Meng
Keyword(s):  
Experimental Studies ◽  
Shake Table Tests ◽  
Rigid Barrier ◽  
Single Degree Of Freedom ◽  
Structural Pounding ◽  
Numerical Studies ◽  
Bridge Model ◽  
On Line ◽  
Potential Damage ◽  
Bridge Responses

Structural pounding can cause considerable damage and even lead to collapse of structures. Most research focuses on modeling, parameter investigation, and mitigation approaches. With the development of structural health monitoring, the on-line detection of pounding becomes possible. The detection of pounding can provide useful information of potential damage of structures. This paper proposed using wavelet scalograms of dynamic response to detect pounding and examined the feasibility of this method. Numerical investigations were performed on a pounding system that consisted of a damped single-degree-of-freedom (SDOF) structure and a rigid barrier. Hertz contact model was used to simulate pounding behavior. The responses and pounding forces of the system under harmonic and earthquake excitations were numerically solved. The wavelet scalograms of acceleration responses were used to identify poundings. It was found that the scalograms can indicate the occurrence of pounding and occurrence time very well. The severity of the poundings was also approximately estimated. Experimental studies were carried out, in which shake table tests were conducted on a bridge model that underwent pounding between its different components during ground motion excitation. The wavelet scalograms of the bridge responses indicated pounding occurrence quite well. Hence the conclusions from the numerical studies were verified experimentally.

scholarly journals How grow-and-switch gravitropism generates root coiling and root waving growth responses in Medicago truncatula

2015 ◽  
Vol 112 (42) ◽  
pp. 12938-12943 ◽  
Author(s):  
Tzer Han Tan ◽  
Jesse L. Silverberg ◽  
Daniela S. Floss ◽  
Maria J. Harrison ◽  
Christopher L. Henley ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Growth Medium ◽  
Plant Root ◽  
Experimental Studies ◽  
Optimal Strategies ◽  
Growth Responses ◽  
Inclined Plane ◽  
Rigid Barrier ◽  
Primary Roots ◽  
Root Waving

Experimental studies show that plant root morphologies can vary widely from straight gravity-aligned primary roots to fractal-like root architectures. However, the opaqueness of soil makes it difficult to observe how environmental factors modulate these patterns. Here, we combine a transparent hydrogel growth medium with a custom built 3D laser scanner to directly image the morphology of Medicago truncatula primary roots. In our experiments, root growth is obstructed by an inclined plane in the growth medium. As the tilt of this rigid barrier is varied, we find Medicago transitions between randomly directed root coiling, sinusoidal root waving, and normal gravity-aligned morphologies. Although these root phenotypes appear morphologically distinct, our analysis demonstrates the divisions are less well defined, and instead, can be viewed as a 2D biased random walk that seeks the path of steepest decent along the inclined plane. Features of this growth response are remarkably similar to the widely known run-and-tumble chemotactic behavior of Escherichia coli bacteria, where biased random walks are used as optimal strategies for nutrient uptake.

Film thickness in elastohydrodynamically lubricated slender elliptic contacts: Part I – numerical studies of central film thickness

2021 ◽  
pp. 135065012110477
Author(s):  
Marius Wolf ◽  
Sergey Solovyev ◽  
Fatemi Arshia
Keyword(s):  
Film Thickness ◽  
State Of The Art ◽  
Experimental Studies ◽  
Elastohydrodynamic Lubrication ◽  
Large Parameter ◽  
Numerical Studies ◽  
Minimum Film Thickness ◽  
Subsequent Publication ◽  
New Formula ◽  
Increasing Load

In this paper, analytical equations for the central film thickness in slender elliptic contacts are investigated. A comparison of state-of-the-art formulas with simulation results of a multilevel elastohydrodynamic lubrication solver is conducted and shows considerable deviation. Therefore, a new film thickness formula for slender elliptic contacts with variable ellipticity is derived. It incorporates asymptotic solutions, which results in validity over a large parameter domain. It captures the behaviour of increasing film thickness with increasing load for specific very slender contacts. The new formula proves to be significantly more accurate than current equations. Experimental studies and discussions on minimum film thickness will be presented in a subsequent publication.

scholarly journals Investigations on Torsion of the Two-Chords Single Laced Members

2017 ◽  
Vol 25 (2) ◽  
pp. 147-160
Author(s):  
Paweł Lorkowski ◽  
Bronisław Gosowski
Keyword(s):  
Cross Sections ◽  
Experimental Studies ◽  
The Finite Element Method ◽  
Second Moment ◽  
Steel Columns ◽  
Numerical Studies ◽  
Traction Network ◽  
Railway Traction ◽  
Parametric Analyses ◽  
The Relationship

Abstract The paper presents experimental and numerical studies to determine the equivalent second moment of area of the uniform torsion of the two-chord steel single laced members. The members are used as poles of railway traction network gates, and steel columns of framed buildings as well. The stiffness of uniform torsion of this kind of columns allows to the determine the critical loads of the spatial stability. The experimental studies have been realized on a single - span members with rotation arrested at their ends, loaded by a torque applied at the mid-span. The relationship between angle of rotation of the considered cross-section and the torque has been determined. Appropriate numerical model was created in the ABAQUS program, based on the finite element method. A very good compatibility has been observed between experimental and numerical studies. The equivalent second moment of area of the uniform torsion for analysed members has been determined by comparing the experimental and analytical results to those obtained from differential equation of non-uniform torsion, based on Vlasov’s theory. Additionally, the parametric analyses of similar members subjected to the uniform torsion, for the richer range of cross-sections have been carried out by the means of SOFiSTiK program. The purpose of the latter was determining parametrical formulas for calculation of the second moment of area of uniform torsion.

scholarly journals Falling weight impact test of a new-type flexible rock-shed

2018 ◽  
Vol 38 (2) ◽  
pp. 242-252
Author(s):  
Jianrong Yang ◽  
Zhiyu Zhang
Keyword(s):  
Experimental Studies ◽  
Steel Tube ◽  
Time Interval ◽  
Explicit Finite Element ◽  
Numerical Studies ◽  
Structural Details ◽  
Tensile Forces ◽  
New Type ◽  
Falling Weight ◽  
The Impact

A new concept of a flexible rock-shed is presented for protection of the railway from falling rocks. The flexible rock-shed is made of flexible nets connected by specific spring spacer bars to an array of reinforced concrete portable frames which are linked by a longitudinal steel tube truss. To evaluate the performance of the flexible rock-shed, experimental and numerical studies are carried out in the present study. Impact tests are conducted on a full-scale partial model of the prototype structure when it is subjected to a falling block of 340 kg. The impact time interval, maximum deflection of the flexible net, tensile forces in the supporting ropes, and axial strains of spring spacer bars are recorded. To further examine the dynamic behavior of the flexible rock-shed, numerical simulations are also carried out by using the explicit finite element code ANSYS/LS-DYNA. It is found that the numerical results coincide well with the experimental data and both the numerical and experimental studies reveal that the structure can withstand impact energy of 50 kJ with all the materials working in the elastic range. The structural details are improved and the basis for the design and construction of similar structures in the future is provided.<br>

Mechanical Behaviour of Steel-Concrete Twin I-Girder Bridges

2018 ◽  
Author(s):  
Weiwei Lin ◽  
Heang Lam ◽  
Teruhiko Yoda
Keyword(s):  
Load Transfer ◽  
Mechanical Performance ◽  
Experimental Studies ◽  
Test Results ◽  
Loading Test ◽  
Girder Bridges ◽  
Bridge Model ◽  
Symmetrical Loading ◽  
Unsymmetrical Loading ◽  
Girder Bridge

<p>Steel-concrete composite twin I-girder bridges have been built a lot in both Europe and Japan, but the lack of redundancy has always been a concern in U.S. and many other countries. In addition, few experimental studies have been performed on the mechanical performance of such bridges, particularly for the intact bridges. On this background, a steel-concrete composite twin I-Girder bridge model was designed according to the current highway bridge design specification in Japan and tested in the laboratory. The static loading tests were performed, and two loading conditions including both symmetrical loading and unsymmetrical loading were applied. Load versus deflection relationships were measured in the loading test, and the failure mode of the test specimen was discussed. The flexural strain development on bottom flanges of two main girders was also reported in this paper to confirm the load transfer between two main girders. In addition, the theoretical results on the basis of the classic theory were also provided to compare with the test results. The comparison indicates that the theoretical analyses can predict the behaviour of the twin I-girder bridges very well in the elastic stage by considering the effective width of the slab. The load transfer paths in such bridges were also discussed on the basis of the test results under un-symmetrical loading.</p>

Identification of promising objects for the synthesis of thiosulphonate derivatives of benzoquinone and hydroquinone

2021 ◽  
Vol 4 (2) ◽  
pp. 47-53
Author(s):  
N. Y. Monka ◽  
◽  
N. E. Stadnytska ◽  
I. R. Buchkevych ◽  
K. O. Kaplia ◽  
...  
Keyword(s):  
Biological Activity ◽  
Biological Activities ◽  
Experimental Studies ◽  
New Drugs ◽  
Reduced Form ◽  
Free Form ◽  
Wide Range ◽  
On Line ◽  
Living Organisms ◽  
Derivatives Of

Benzoquinone and its reduced form hydroquinone belong to phenolic compounds and are found in living organisms in free form or in glycosides. They are active substances of some medicinal plants and have a pharmacological effect on the human body. Accordingly, their derivatives are important objects for chemical synthesis and development of new drugs. This article presents the findings of the structural design of substances with benzoquinone or hydroquinone fragment and sulfur-containing compound. By use of appropriate on-line programs a predictive screening of the biological activity and cytotoxicity of thiosulfonate derivatives of benzoquinone and hydroquinone has been conducted. It has been found that they have immense methodological potential to be synthesized by substances with a wide range of biological activities and a high value of probable activity, which substantiates the feasibility of conducting experimental studies on their biological activity, particularly anticancer.

scholarly journals A Review on the Control Parameters of Natural Convection in Different Shaped Cavities with and without Nanofluid

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1011 ◽  
Author(s):  
Sara Rostami ◽  
Saeed Aghakhani ◽  
Ahmad Hajatzadeh Pordanjani ◽  
Masoud Afrand ◽  
Goshtasp Cheraghian ◽  
...  
Keyword(s):  
Porous Media ◽  
Natural Convection ◽  
Free Convection ◽  
Forced Convection ◽  
Opposite Effect ◽  
Fluid Velocity ◽  
Experimental Studies ◽  
Effective Parameters ◽  
Magnetic Forces ◽  
Numerical Studies

Natural convection in cavities is an interesting subject for many researchers. Especially, in recent years, the number of articles written in this regard has grown enormously. This work provides a review of recent natural convection studies. At first, experimental studies were reviewed and, then, numerical studies were examined. Then, the articles were classified based on effective parameters. In each section, numerical studies were examined the parameters added to the cavity such as magnetic forces, fin, porous media and cavity angles. Moreover, studies on non-rectangular cavities were investigated. Free convection in enclosures depends more on the fluid velocity relative to the forced convection, leading to the opposite effect of some parameters that should essentially enhance rate of heat transfer. Nanoparticle addition, magnetic fields, fins, and porous media may increase forced convection. However, they can reduce free convection due to the reduction in fluid velocity. Thus, these parameters need more precision and sometimes need the optimization of effective parameters.

Fatigue-Ratcheting Behavior of 6 in Pressurized Carbon Steel Piping Systems Under Seismic Load: Experiments and Analysis

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
A. Ravi Kiran ◽  
G. R. Reddy ◽  
P. N. Dubey ◽  
M. K. Agrawal
Keyword(s):  
Carbon Steel ◽  
Response Spectrum ◽  
Thickness Variation ◽  
Seismic Load ◽  
Frequency Change ◽  
Shake Table Tests ◽  
Numerical Studies ◽  
Piping Systems ◽  
Earthquake Load ◽  
Steel Piping

This article presents the experimental and numerical studies of fatigue-ratcheting in carbon steel piping systems under internal pressure and earthquake load. Shake table tests are carried out on two identical 6 in pressurized piping systems made of carbon steel of grade SA333 Gr 6. Tests are carried out using similar incremental seismic load till failure. Wavelet analysis is carried to evaluate frequency change during testing. The tested piping systems are analyzed using iterative response spectrum (IRS) method, which is based on fatigue-ratcheting and compared with test results. Effect of thickness variation in elbow on strain accumulation is studied. Excitation level for fatigue-ratcheting failure is also evaluated and the details are given in this paper.

Modeling and CFD Analyses of Gear Pump in OpenFOAM

2019 ◽  
Author(s):  
G. Shoukat ◽  
Kamran Siddique ◽  
M. Sajid
Keyword(s):  
Power Flow ◽  
Experimental Studies ◽  
Research Area ◽  
Peak Performance ◽  
Gear Pump ◽  
Numerical Studies ◽  
Gear Pumps ◽  
Cfd Analyses ◽  
Dynamic Meshing ◽  
Pressure Output

Abstract Turbomachinery plays a key role in process and manufacturing industries. The interplay between power, flow rates and pressure output remain an interesting research area. To support specific processes in the industry, each pump or compressor must be fine-tuned for peak performance. As trend shifts from large organizations to entrepreneurial startups, spending significant costs on licensing of commercially available CFD softwares becomes unfeasible. This paper investigates the use of OpenFOAM – open source CFD package towards the analysis of gear pumps. The solution employs dynamic meshing and snappyHexMesh library in a single study. To validate the numerical model developed under OpenFoam’s environment, experimental studies were carried out. The pressure output of the pump was measured at four different RPMs — 200, 250, 300 and 400. An excellent agreement between experimental and numerical studies was seen at relatively higher RPMs. The numerical studies further explored the pulsating flow, recorded the variation between a constant maximum and minimum pressure value for each RPM. The variation in pressure was observed to increase at higher RPMs. The agreement between experimental and numerical findings established the utility of OpenFoam in investigating pump action.

Reduced-Order Modeling and Experimental Studies of Two-Way Coupled Fluid-Structure Interaction in Flapping Wings

2019 ◽  
Author(s):  
Ryan K. Schwab ◽  
Heidi E. Reid ◽  
Mark A. Jankauski
Keyword(s):  
Fluid Structure Interaction ◽  
Experimental Studies ◽  
Flapping Wing ◽  
Flexible Wings ◽  
Single Degree Of Freedom ◽  
Fluid Structure ◽  
Reduced Order ◽  
Structure Interaction ◽  
Rotation Stage ◽  
Computational Resources

Abstract Flapping, flexible wings deform under both aerodynamic and inertial loads. However, the fluid-structure interaction (FSI) governing flapping wing dynamics is not well understood. Conventional FSI models require excessive computational resources and are not conducive to parameter studies that consider variable wing kinematics or geometry. Here, we present a simple two-way coupled FSI model for a wing subjected to single-degree-of-freedom (SDOF) rotation. The model is reduced-order and can be solved several orders of magnitude faster than direct computational methods. We construct a SDOF rotation stage and measure basal strain of a flapping wing in-air and in-vacuum to study our model experimentally. Overall, agreement between theory and experiment is excellent. In-vacuum, the wing has a large 3ω response when flapping at approximately 1/3 its natural frequency. This response is attenuated substantially when flapping in-air as a result of aerodynamic damping. These results highlight the importance of two-way coupling between the fluid and structure, since one-way coupled approaches cannot describe such phenomena. Moving forward, our model enables advanced studies of biological flight and facilitates bio-inspired design of flapping wing technologies.

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