A Simplified Dynamic Analysis of Existing Pedestrian Bridges, a Possibility to get new Experience for Designing

2021 ◽  
Author(s):  
Niklas Johansson
Keyword(s):  
Dynamic Behaviour ◽  
Dynamic Properties ◽  
Rapid Development ◽  
Theoretical Models ◽  
Valuable Insight ◽  
Fundamental Vibration ◽  
Daily Work ◽  
Existing Structures ◽  
Pedestrian Bridges ◽  
The Time Domain

<p>Technology gives us new instruments that can help us in our daily work. There is a rapid development of different kinds of sensors used in buildings, bridges, towers and other structures. These sensors can help us gather much information from our existing structures, which gives us the possibility to use a large amount of data obtained from real structures to evaluate our theoretical models used in the design and refine them.</p><p>In the topic of pedestrian bridges, it is interesting to evaluate their dynamic properties since they are sensible to the dynamic vertical and horizontal loads from people. The fundamental data for the dynamic behaviour of a pedestrian bridge are the eigenfrequencies, which can be obtained easily using an accelerometer. Today there is almost always one available since the mobile phones are equipped with them. With an application, it is easy to obtain the fundamental vibration frequency for a bridge and it is also possible to analyse the higher vibration modes in a frequency spectrum. Furthermore, it is easy to obtain a measurement of acceleration in the time domain from walking or running. Also the damping has a very important effect on the vibration level, and it can also be evaluated with measurements.</p><p>This tool can be used for evaluating a similar structure as the one to be designed and it could provide us with valuable insight in the dynamic behaviour of the structure. This paper presents some examples, where the theoretical results from models are compared with measurements of the finished bridges. The results from measurements are validated with a simple, well known structure.</p>

Managing Flow Induced Vibration in Subsea Jumpers

2021 ◽  
Author(s):  
Rakshith Naik ◽  
Yetzirah Urthaler ◽  
Scot McNeill ◽  
Rafik Boubenider
Keyword(s):  
Dynamic Properties ◽  
Fatigue Analysis ◽  
Management Program ◽  
Measured Data ◽  
Operating Conditions ◽  
Valuable Insight ◽  
Fe Model ◽  
Flow Induced Vibration ◽  
Vibration Measurements

Abstract Certain subsea jumper design features coupled with operating conditions can lead to Flow Induced Vibration (FIV) of subsea jumpers. Excessive FIV can result in accumulation of allowable fatigue damage prior to the end of jumper service life. For this reason, an extensive FIV management program was instated for a large development in the Gulf of Mexico (GOM) where FIV had been observed. The program consisted of in-situ measurement, modeling and analysis. Selected well and flowline jumpers were outfitted with subsea instrumentation for dedicated vibration testing. Finite Element (FE) models were developed for each jumper and refined to match the dynamic properties extracted from the measured data. Fatigue analysis was then carried out using the refined FE model and measured response data. If warranted by the analysis results, action was taken to mitigate the deleterious effects of FIV. Details on modeling and data analysis were published in [5]. Herein, we focus on the overall findings and lessons learned over the duration of the program. The following topics from the program are discussed in detail: 1. In-situ vibration measurement 2. Overall vibration trends with flow rate and lack of correlation of FIV to flow intensity (rho-v-squared); 3. Vibration and fatigue performance of flowline jumpers vs. well jumpers 4. Fatigue analysis conservatism Reliance on screening calculations or predictive FE analysis could lead to overly conservative operational limits or a high degree of fatigue life uncertainty in conditions vulnerable to FIV. It is proposed that in-situ vibration measurements followed by analysis of the measured data in alignment with operating conditions is the best practice to obtain a realistic understanding of subsea jumper integrity to ensure safe and reliable operation of the subsea system. The findings from the FIV management program provide valuable insight for the subsea industry, particularly in the areas of integrity management of in-service subsea jumpers; in-situ instrumentation and vibration measurements and limitations associated with predictive analysis of jumper FIV. If learnings, such as those discussed here, are fed back into design, analysis and monitoring guidelines for subsea equipment, the understanding and management of FIV could be dramatically enhanced compared to the current industry practice.

scholarly journals Application of Polymers as a Tool in Crystallization—A Review

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2695
Author(s):  
Marcin Lemanowicz ◽  
Anna Mielańczyk ◽  
Tomasz Walica ◽  
Milena Kotek ◽  
Andrzej Gierczycki
Keyword(s):  
Crystallization Process ◽  
Rapid Development ◽  
Theoretical Models ◽  
Crystalline Materials ◽  
Crystal Properties ◽  
Efficient Control ◽  
Water And Wastewater ◽  
Controlled Crystallization ◽  
Scientific Periodicals ◽  
Induced Crystallization

The application of polymers as a tool in the crystallization process is gaining more and more interest among the scientific community. According to Web of Science statistics the number of papers dealing with “Polymer induced crystallization” increased from 2 in 1990 to 436 in 2020, and for “Polymer controlled crystallization”—from 4 in 1990 to 344 in 2020. This is clear evidence that both topics are vivid, attractive and intensively investigated nowadays. Efficient control of crystallization and crystal properties still represents a bottleneck in the manufacturing of crystalline materials ranging from pigments, antiscalants, nanoporous materials and pharmaceuticals to semiconductor particles. However, a rapid development in precise and reliable measuring methods and techniques would enable one to better describe phenomena involved, to formulate theoretical models, and probably most importantly, to develop practical indications for how to appropriately lead many important processes in the industry. It is clearly visible at the first glance through a number of representative papers in the area, that many of them are preoccupied with the testing and production of pharmaceuticals, while the rest are addressed to new crystalline materials, renewable energy, water and wastewater technology and other branches of industry where the crystallization process takes place. In this work, authors gathered and briefly discuss over 100 papers, published in leading scientific periodicals, devoted to the influence of polymers on crystallizing solutions.

scholarly journals Performance of a Suspension Bridge with Active Vibration Dampers

2018 ◽  
Vol 196 ◽  
pp. 01017
Author(s):  
Anatolij Konovalov ◽  
Marina Pustovalova
Keyword(s):  
Cross Sections ◽  
Dynamic Properties ◽  
Suspension Bridge ◽  
Suspension Bridges ◽  
Initial Model ◽  
Strain Behavior ◽  
Pedestrian Bridges ◽  
Active Vibration ◽  
Active Damper ◽  
Vibration Dampers

Suspended structures that are used extensively in construction of motorway and pedestrian bridges allow bridging wide spans without having to install intermediate supports. Being less stiff in comparison to girder and arch bridges, suspension bridges require their dynamic properties to be controlled [1, 2]. This is a vital task when it comes to suspension bridges. Several engineering arrangements are available to control the dynamic properties of the structures [3]. This paper addresses the use of active dampers [4] installed on the tops of the towers as the means to control vibrations of a suspension bridge. To this end, a planar 3D model of suspension bridge was built using ANSYS software. The authors compared stress-strain behavior and dynamic properties of the models with and without active vibration dampers. In contrast to the initial model, the model of a bridge equipped with active dampers exhibits less displacement in all cross-sections. Thus, the displacements are reduced 1.7 times in the middle of the central span of suspended stiffening truss; 2.7 times in the middle of the end span; and displacements of the top of the bridge tower are 1.6 times less. The modal analysis has shown that in the model with active dampers the frequency of transverse vibrations at the tower tops has increased 1.9 times, while vertical vibrations have increased within 23%. Under maximum applied overpressure in the active damper, torsional vibrations of the structure have increased 2.4 times as compared to the initial model. The results obtained by the authors allow for the conclusion that active dampers are useful tools for controlling the dynamic properties of a suspension bridge.

Experiences of the Mass Media

2015 ◽  
pp. 129-140
Author(s):  
Anne Eyre ◽  
Pam Dix
Keyword(s):  
Mass Media ◽  
Mobile Phones ◽  
Rapid Development ◽  
Colleges And Universities ◽  
Valuable Insight ◽  
Next Generation ◽  
Human Interest ◽  
The Mass Media ◽  
Research Students ◽  
Insight Into

This chapter studies how the human interest angle has always made bereaved people and survivors attractive to the mass media. The advent of 24-hour news has also meant increasing pressure to find stories to fill the time, leading to more speculative reporting, while the facts are being established. The rapid development of technology means that disasters can now be captured on video or mobile phones as they unfold. This potentially offers rapid news and updates and valuable insight into disaster experiences. But it also encourages the acquisition and dissemination of images that may be distasteful, exploitative, and harmful to the feelings, rights, and welfare of those affected by disasters. Disaster Action members have sought to influence journalists' perceptions and treatment of those they seek to interview. This includes giving presentations to journalism and research students at colleges and universities, contributing to the work of the Dart Centre for Journalism and Trauma, and the production of a leaflet with guidance on interviewing, which spells out what it is like to be on the receiving end. One of the most rewarding parts of this work is contributing to education for the next generation of journalists.

scholarly journals Structural Behavior of the General Archive of the Nation (AGN) Building, Mexico

2018 ◽  
Vol 3 (3) ◽  
pp. 39
Author(s):  
Marcos Chávez ◽  
Fernando Peña ◽  
Claudia Cruz ◽  
Gustavo Monroy
Keyword(s):  
Dynamic Properties ◽  
Ambient Vibration ◽  
Structural Behavior ◽  
High Plasticity ◽  
Fundamental Vibration ◽  
Vibration Period ◽  
Ambient Vibration Tests ◽  
Smeared Crack ◽  
The Government ◽  
Vibration Tests

This article presents a study on the structural behavior of the Government Building that is part of the old Lecumberri Palace and which currently houses the Mexican General Archive of the Nation. This building was inaugurated in 1900 and closed in 1976, after serving as a prison for 76 years. It was reopened in 1982 after it had undergone several remodeling works. The construction is made of brick masonry with lime mortar. It is supported by a deposit of overly compressible high-plasticity clays. The main problems of this building are the appearance of cracks in both interior and exterior walls, and moisture in the ground floor, caused by differential settlements. The study entailed a geometric and a damage survey as well as ambient vibration tests in order to determine the dynamic properties of the construction. The data obtained was used for the making of a model that, using the finite element method, was analyzed under different load conditions. This study has focused on the overall response with the assumption of smeared crack damage. According to the results, the building’s safety was deemed as acceptable. It has the capability to withstand seismic actions as established by the Mexican Building Code due to the high density of its walls and the resulting stiffness, which infer that the fundamental vibration period of the building would be distant from the predominant vibration period of the soil. This highlights the idea that the building’s critical condition is constituted by the differential settlements, which cause damage in the construction.

scholarly journals Fractional-Order SIR Epidemic Model for Transmission Prediction of COVID-19 Disease

2020 ◽  
Vol 10 (23) ◽  
pp. 8316
Author(s):  
Kamil Kozioł ◽  
Rafał Stanisławski ◽  
Grzegorz Bialic
Keyword(s):  
Fractional Order ◽  
Epidemic Model ◽  
Dynamic Properties ◽  
Sir Model ◽  
Domain Model ◽  
Sir Epidemic Model ◽  
Step Method ◽  
Order Difference ◽  
Sir Epidemic ◽  
The Time Domain

In this paper, the fractional-order generalization of the susceptible-infected-recovered (SIR) epidemic model for predicting the spread of the COVID-19 disease is presented. The time-domain model implementation is based on the fixed-step method using the nabla fractional-order difference defined by Grünwald-Letnikov formula. We study the influence of fractional order values on the dynamic properties of the proposed fractional-order SIR model. In modeling the COVID-19 transmission, the model’s parameters are estimated while using the genetic algorithm. The model prediction results for the spread of COVID-19 in Italy and Spain confirm the usefulness of the introduced methodology.

Some Dynamic Properties of Contact Patches in Bolted Joints

2017 ◽  
Author(s):  
Damien P. T. Lancereau ◽  
Hugh G. D. Goyder ◽  
Philip Ind ◽  
Daniel Brown
Keyword(s):  
Dynamic Behaviour ◽  
Dynamic Properties ◽  
Relative Displacement ◽  
Bolted Joints ◽  
Nonlinear Behaviour ◽  
Bolted Joint ◽  
Clear Trend ◽  
Contact Patch ◽  
New Interpretation ◽  
Instantaneous Frequencies

The dynamics of structures built-up from components connected by bolted joints are not well understood. Experiments were conducted with bolted joints in a shear configuration in which instantaneous vibration frequencies and damping could be measured. A system with bolted joints was excited and the free vibration decay measured. As the vibration decays, the damping decreases and the frequencies increase. This suggests a new interpretation for the contact patch in a bolted joint, involving bound, slipping and alternating regions. The changing size of the bound region controls the instantaneous frequencies and the relative displacement inside the slipping region and the alternating region controls the damping behaviour. Shims of different lengths enabled the behaviour of the contact patch to be investigated. A clear trend exists between the length of the shims and the non-linear dynamic behaviour. The introduction of multiple shims did not increase the damping or alter the dynamic nonlinear behaviour. The introduction of grease into the bolted joint increased the damping but oil did not. The vibration measurements enable the size of the contact patch to be estimated.

Identification of the Dynamic Characteristics of Long Annular Seals Using a Time Domain Technique

1998 ◽  
Vol 120 (3) ◽  
pp. 705-712 ◽  
Author(s):  
M. Ismail ◽  
R. D. Brown
Keyword(s):  
Dynamic Characteristics ◽  
Time Domain ◽  
Theoretical Models ◽  
Rotational Frequency ◽  
Singular Value Decomposition Method ◽  
Damping Coefficients ◽  
Theoretical Predictions ◽  
The Time Domain ◽  
Value Decomposition ◽  
Annular Seals

This paper describes experimental results from a research program aimed at a study of the static and dynamic characteristics of liquid long annular seals. A seal test rig permits the identification in the time domain of mass, stiffness, and damping coefficients using a least-squares technique based on the singular value decomposition method. The experimental method relies on the forced excitation of a flexibly supported stator by two hydraulic shakers. The forcing signal is composed from a small number of frequencies which are not related to the rotational frequency of the rigid shaft rotating inside the stator. The test data consisting of two inertia, four stiffness, and four damping coefficients is compared with theoretical predictions based on two theoretical models: (i) the model of Black et al. (1971 and 1981) and (ii) the model of Childs and Kim (1985).

Spin-labelled nucleic acids

1981 ◽  
Vol 14 (2) ◽  
pp. 223-288 ◽  
Author(s):  
S. G. Kamzolova ◽  
G. B. Postnikova
Keyword(s):  
Nucleic Acids ◽  
Spin Label ◽  
Dynamic Behaviour ◽  
Protein Complexes ◽  
Dynamic Properties ◽  
Biological Systems ◽  
Spin Labels ◽  
Esr Spectrum ◽  
Label Method ◽  
Conformational Properties

The spin label method developed by McConnell 15 years ago is now widely used in studies of the structure and dynamic properties of a variety of the biological systems such as proteins and protein complexes, lipids and membranes, nucleic acids, nucleoproteins, etc.The ESR spectrum of the nitroxide radcal – the spin label – is very sensitive to its microenvironment and permits easy registration of even subtle alterations in it. If spin labels are attached to different sites of a macromolecule the information can be gained about conformational properties of all these local regions and, as a result, about the dynamic behaviour of the object as a whole.

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