DOCSLIB.ORG

Modal Analysis of Ship's Mast Structure Using Effective Mass

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Modal Analysis of Ship's Mast Structure Using Effective Mass ISSN (Print) : 0974-6846 Indian Journal of Science and Technology, Vol 9(21), DOI: 10.17485/ijst/2016/v9i21/94830, June 2016 ISSN (Online) : 0974-5645 Modal Analysis of Ship’s Mast Structure using Effective Mass Participation Factor Muhammad Sajjad Ahmad1*, Mohsin Jamil1, Javid Iqbal1, Muhammad Nasir Khan1, Mazhar Hussain Malik2 and Shahid Ikramullah Butt1 1School of Mechanical and Manufacturing Engineering (SMME), National University of Sciences and Technology (NUST), H-12 Main Campus, Islamabad, Pakistan; [email protected], [email protected], [email protected], [email protected], [email protected] 2Department of Computer Science, Institute of Southern Punjab, Multan, Pakistan; [email protected] Abstract Background/Objectives: Each structure tends to vibrate at particular frequencies, called resonant or natural frequencies. When a structure is excited by dynamic load with frequency coinciding one of its natural frequencies the structure the vibration problem in the ship mast. Methods/Statistical Analysis: measure­experiences of the­stresses energy­and contained­large­displacements. within each resonant­In­this­ mode.paper­ Vibrationeffective­mass problem­participation originated­factor when­criterion one of the­is antenna­used­to ­atsolve top ­ of mast was replaced by a new antenna with greater mass at same location.­The­effective The overall­mass mast­participation structure ­startedfactor­provides vibrating­a­ because of the resonance of natural frequencies of the mast structure with natural frequencies of rotary equipment. Findings: It caused interruption in sensitivity of equipment installed on the mast structure. Instead of fabricating the new mast structure, some alteration has been carried out on the basis of results obtained from modal analysis. Application/ Improvements: The­study­is­very­effective­to­overcome­the­vibration­problems­in­ship­mast. Keywords: ­Effective­Mass­Participation,­Modal­Analysis,­Mode­Shape,­Ship­Mast 1. Introduction properties or the boundary conditions of a structure change, its modes of vibration will modify4. It is well known that mechanical structures can resonate, i.e. small forces can result in deformation. Resonance can likewise harm the complete structure. Resonant vibra- 2. Effective Mass Participation tion is essentially brought on by an interaction between Factor (EMPF) Method the inertial and elastic properties of the materials inside of a structure1. Resonance is often a contributing factor The Effective Mass Participation Factor (EMPF) provides to many of the vibration and noise related problems that a measure of the energy contained within each resonant occur in structures and operational machinery. The reso- mode. It represents the quantity of system mass participat- 5 nant frequencies of a structure should be identified and ing in a particular mode . For a particular structure, with measured to better see structural behavior2. a mass matrix [M], normal mode shapes and a ground Modal analysis has turned into a far reaching method motion influence coefficient r, participation of each mode for finding the modes of vibration of a machine or struc- can be obtained as the effective mass participation factor, 3 ture . Modes are inherent properties of a structure, and are →T ϕ Mr determined by the material properties (mass, damping, = i pi →→T 2 (1) and stiffness), and boundary conditions of the struc- ()ϕϕi M i ture. Each mode is characterized by a natural frequency, A mode with a large effective mass is generally a major modal damping, and a mode shape. Either the material contributor to the response of the system. It is possible to *Author for correspondence Modal Analysis of Ship’s Mast Structure using Effective Mass Participation Factor calculate an EMPF for a particular direction (x, y or z). Table 1. Maximum Limit for Top of Ship Mast The sum of the effective masses for all modes in a given Mechanical Test Top of Mast Limits Standard response direction must be equal to the total mass of the Amp ± 1mm to 16 Hz structure. Priestley et al. confirm that a sum of all EMPF 10m/s2 16 to 23 Hz (known as Cumulative Effective Mass Participation Factor, Vibration (MIL-STD 810 G) CEMPF) of 80% to 90% in any given response direction Endurance 30 minute can be considered sufficient to capture the dominant ± 1 mm to 16 Hz dynamic response of the structure6. n 4. Modal Analysis of Mast 80 ≤≤100 p 90 (2) ∑i=1 i Structure Where n is the number of modes taken under consideration. If we expect a vibration in the x-direction, 4.1 Modeling of Structure we need to keep calculating modes until the sum of all Antenna installed on top of the Mast was replaced with a EMPF in the x-direction is about 80-90%. We need con- new antenna having 80Kg weight (which is 50 kg heavier sistency in the results to compare the exciting frequency than previous). Due to change in mass at top of the mast, with the sufficient natural frequencies7. the mast structure started to vibrate during cruising of the ship. Also data receiving from antenna was distorted and wrong due to vibrations. This problem was sent for finite 3. Rules and Standards element analysis and proposal of a solution to cater vibra- for Modal Analysis tions in ship mast. The frequency of equipment installed on the ship at various speed is mentioned in Table 2. 3.1 BV Rules Material used in mast structure was Aluminum. ʋ As stated by bureau VERITAS rules for naval ships,“ each Young’s modulus (E), Poisson ratio ( ) and density (ρ) 3 normal mode frequency f i (Hz) of the ship mast should of Aluminum are71000MPa,0.3 and 2700 kg/m respec- N tively. Three equipments installed on ship mast with 320 be in compliance with one of the following formulae: kg, 62kg and 80 kg mass respectively. 08. ffEM()IN >>Ni 12. fEM()AX (3) 4.2 Modal Analysis of Mast Structure where fE(MIN)(Hz) and fE(MAX) (Hz) are the minimum and the maximum possible excitations frequencies respec- Frequencies which amplify the effect of load on a tively due to the ship’s motions or the propulsion system structure are identified by modal analysis. It is also used to find the mode shapes of a structure. The displacement at the following speeds;- cruise speed and maximum shape of modes provides enough information about loose continuous rate speed. At the point when the dynamic component(s) or missing constraints. The model will have analysis depends on normal modes, their number is, all six rigid body modes if a single component has no con- in all, to be such that the modal effective mass is at the straints. They correspond to the component translating very least 95% of the mass of the system constituted by respectively in X, Y and Z and rotating about X, Y and Z. the mast and its supporting structure. The modal effective Mode at an inconvenient frequency needs to be moved or mass is defined as. rather change the frequency of the mode. The frequency N can be amplified or lessened according to requirements of g2 (4) ∑i=1 i the structure. For a single degree of freedom spring-mass, the natural frequency is, Where γi is the ith modal participation factor and N is the 8 number of the considered normal modes” . 1 k f = (5) n 2p m 3.2 Military Standards Where m is the mass and k is the spring stiffness. The maximum vibration limits for top of the ship mast are Increasing the natural frequency requires a decrease in given in Table 19,10. m or an increase in k. Finite element model of existing 2 Vol 9 (21) | June 2016 | www.indjst.org Indian Journal of Science and Technology Muhammad Sajjad Ahmad, Mohsin Jamil, Javid Iqbal, Muhammad Nasir Khan, Mazhar Hussain Malik and Shahid Ikramullah Butt mast structure with initial stiffening and equipment loads the displacements are greater than the limits defined in applied on the mast structure by using point mass element the standards. By plotting all the mode shapes it can be are shown in Figure 1. interpreted that the main reason of the resonance is weak Mast structure was modeled by using beam and shell stiffness at the top and middle of the mast structure. modal. All the pipe structure was modeled by using the At this stage the Effective Mass Participation Factor beam-189 element type whereas plates were modeled (EMPF) becomes the critical point as all the modes are using shell-181 element. Mass 21 was used for equipment not actively participating in the resonance of structure. mass. The element edge length of meshing was 50 mm for As a next step the effective mass participation factor of both pipes and plates. Hence the total number of elements each mode in checked and modes participating having was 1200. Different modes were extracted using modal more than 1% EMPF are segregated and also verified the analysis in ANSYS 15.0. Mode shape of mast structure at Cumulative Effective Mass Participation Factor (CEMPF) different frequencies (only critical) is shown in Figure 2. which should be between 80-90 %. Relative displacements The results in Figure 2 shows that almost all the are obtained from modal analysis (free vibration analysis). frequencies are producing the resonance according to All 40 modes are causing resonance in the structure but BV Rules limits. Also the results are not validating the after applying effective mass participation factor criteria, Military Standard Limits for Vibration of Mast because following modes are participating more than 1% and also not validating the Military Standardʺ Limits for Vibration ʺ Table 2. Frequency of Equipment installed on the hence these are critical. ʺ ʺ Ship The results shown in Tableʺ 3 that by applying the ʺ 1% EMPF criteria the modes producing effective reso- Sr.
Load more

Recommended publications
  • Modal Analysis of Dynamic Behavior of Buildings Allowed to Uplift at Mid-Story
    Modal Analysis of Dynamic Behavior of Buildings Allowed to Uplift at Mid-story T. Ishihara Building Research Institute, Japan T. Azuhata National Institute for Land and Infrastructure Management, MLIT,Japan M. Midorikawa Hokkaido University, Japan SUMMARY: In this paper, dynamic behavior of buildings allowed to uplift at mid-story is investigated. The system considered is a two dimensional uniform shear-beam model allowed to uplift at mid-story. On account of piece-wise linear characteristics, classical modal analysis is applied to evaluate dynamic behavior during uplift. At first, the equations of motion are derived and eigenproblem is solved. Their free-vibrational responses under gravity are analyzed during the first excursion of uplift following to the first mode vibration in contact phase. Parameters are height/width ratio of whole buildings, height ratio of mid-story uplift system and intensity of vibration. The results show reduction effect due to uplift at mid-story with modal contributions to responses. Keywords: Uplift at mid-story, Uniform shear beam, Story shear coefficient 1. INTRODUCTION It has been pointed out that buildings during strong earthquakes have been subjected to foundation uplift (Rutenberg et al. 1982, Hayashi et al. 1999). Some studies dealing with foundation uplift in flexible systems have already been conducted (e.g. Muto et al. 1960, Meek 1975, 1978, Psycharis 1983, Yim et al. 1985). The authors also studied experimentally and analytically from the point of view of utilizing transient uplift motion for reduction of seismic-force response (e.g. Ishihara et al. 2006a, 2006b, 2007, 2008, 2010, Azuhata et al. 2008, 2009, Midorikawa et al.
    [Show full text]
  • Modal Analysis1
    © 1994 by Eric Marsh & Alexander Slocum Precision Machine Design Topic 10 Vibration control step 1: Modal analysis1 Purpose: The manner in which a machine behaves dynamically has a direct effect on the quality of the process. It is vital to be able to measure machine performance. Outline: • Introduction • Measurement process outline • Practical issues • Vibration fundamentals • Experimental results • Data collection: Instrumentation summary • Case study: A wafer cassette handling robot • Case study: A precision surface grinder "There is nothing so powerful as truth" Daniel Webster 1 This section was written by Prof. Eric Marsh, Dept. of Mechanical Engineering, Penn State University, 322 Reber Bldg., University Park, State College, 16802; [email protected] 10-1 © 1994 by Eric Marsh & Alexander Slocum Introduction • Experimental Modal Analysis allows the study of vibration modes in a machine tool structure. • An understanding of data acquisition, signal processing, and vibration theory is necessary to obtain meaningful results. • The results of a modal analysis are: • Modal natural frequencies • Modal damping factors • Vibration mode shapes • This information may be used to: • Locate sources of compliance in a structure • Characterize machine performance • Optimize design parameters • Identify the weak links in a structure for design optimization •Identify modes which are being excited by the process (e.g., an end mill) so the structure can be modified accordingly. • Identify modes (parts of the structure) which limit the speed of operation (e.g., in a Coordinate Measuring Machine). •Use modal analysis to measure an older machine that achieves high surface finish, but is to be replaced with a more accurate machine. • The new machine can be specified to have a dynamic stiffness at least as high as the old machine.
    [Show full text]
  • Modal Analysis for Free Vibration of Four Beam Theories
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/315549591 MODAL ANALYSIS FOR FREE VIBRATION OF FOUR BEAM THEORIES Conference Paper · January 2015 DOI: 10.20906/CPS/COB-2015-0991 CITATIONS READS 10 615 2 authors: Anderson Soares Da Costa Azevêdo Simone dos Santos Universidade Federal do Piauí 8 PUBLICATIONS 17 CITATIONS 22 PUBLICATIONS 24 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Dynamic Analysis of Beam View project Natural Frequency Optimization using Genetic Algorithm View project All content following this page was uploaded by Simone dos Santos on 27 July 2017. The user has requested enhancement of the downloaded file. MODAL ANALYSIS FOR FREE VIBRATION OF FOUR BEAM THEORIES Anderson Soares da Costa Azevêdo Universidade Federal do Piauí [email protected] Simone dos Santos Hoefel Universidade Federal do Piauí [email protected] Abstract. Beams are structural elements frequently used for support buildings, part of airplanes, ships, rotor blades and most engineering structures. In many projects it is assumed that these elements are subjected only to static loads, how- ever dynamic loads induce vibrations, which changes the values of stresses and strains. Furthermore, these mechanical phenomenon cause noise, instabilities and may also develop resonance, which improves deflections and failure. Therefore study these structural behavior is fundamental in order to prevent the effects of vibration. The mechanical behavior of these structural elements may be described by differential equations, four widely used beam theories are Euler-Bernouli, Rayleigh, Shear and Timoshenko. This paper presents a comparison between these four beam theories for the free trans- verse vibration of uniform beam.
    [Show full text]
  • Seismic Vulnerability Assessment Using Ambient Vibrations : Method and Validation Clotaire Michel, Philippe Guéguen
    Seismic Vulnerability assessment using ambient vibrations : method and validation Clotaire Michel, Philippe Guéguen To cite this version: Clotaire Michel, Philippe Guéguen. Seismic Vulnerability assessment using ambient vibrations : method and validation. 1st International Operational Modal Analysis Conference, Apr 2005, Copen- hagen, Denmark. p 337-344. hal-00071046 HAL Id: hal-00071046 https://hal.archives-ouvertes.fr/hal-00071046 Submitted on 23 May 2006 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. SEISMIC VULNERABILITY ASSESSMENT USING AMBIENT VIBRATIONS: METHOD AND VALIDATION Clotaire Michel, Laboratoire de Géophysique Interne et Tectonophysique, Université Joseph Fourier Grenoble, France Philippe Guéguen, Laboratoire de Géophysique Interne et Tectonophysique, Université Joseph Fourier Grenoble, LCPC, France [email protected] Abstract Seismic vulnerability in wide areas is usually assessed in the basis of inventories of structural parameters of the building stock, especially in high hazard countries like USA or Italy. France is a country with moderate seismicity so that it requires lower-cost methods. Ambient vibrations analyses seem to be an alternative way to determine the vulnerability of buildings. The modal parameters we extract from these recordings give us a 1D model for each class of building found in the study area.
    [Show full text]
  • A Phase Resonance Approach for Modal Testing of Structures with Nonlinear Dissipation
    Journal of Sound and Vibration 435 (2018) 56–73 Contents lists available at ScienceDirect Journal of Sound and Vibration journal homepage: www.elsevier.com/locate/jsvi A phase resonance approach for modal testing of structures with nonlinear dissipation Maren Scheel a,∗,SimonPeterb,RemcoI.Leineb, Malte Krack a a Institute of Aircraft Propulsion Systems, University of Stuttgart, Pfaffenwaldring 6, 70569 Stuttgart, Germany b Institute for Nonlinear Mechanics, University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany article info abstract Article history: The concept of nonlinear modes is useful for the dynamical characterization of nonlinear Received 21 December 2017 mechanical systems. While efficient and broadly applicable methods are now available for the Revised 2 May 2018 computation of nonlinear modes, nonlinear modal testing is still in its infancy. The purpose of Accepted 4 July 2018 this work is to overcome its present limitation to conservative nonlinearities. Our approach Available online XXX Handling Editor: Weidong Zhu relies on the recently extended periodic motion concept, according to which nonlinear modes of damped systems are defined as family of periodic motions induced by an appropriate artificial excitation that compensates the natural dissipation. The particularly simple experi- Keywords: mental implementation with only a single-point, single-frequency, phase resonant forcing is Nonlinear modes analyzed in detail. The method permits the experimental extraction of natural frequencies, Nonlinear system identification Nonlinear modal analysis modal damping ratios and deflection shapes (including harmonics), for each mode of inter- Jointed structures est, as function of the vibration level. The accuracy, robustness and current limitations of the Force appropriation method are first demonstrated numerically.
    [Show full text]
  • Dynamic Analysis of Cantilever Beam and Its Experimental Validation
    DYNAMIC ANALYSIS OF CANTILEVER BEAM AND ITS EXPERIMENTAL VALIDATION A Thesis submitted in partial fulfillment of the requirements for the Degree of Bachelor of Technology In Mechanical Engineering By Subhransu Mohan Satpathy Roll No: 110ME0331 Praveen Dash Roll No: 110ME0289 Department of Mechanical Engineering National Institute Of Technology Rourkela - 769008 1 National Institute of Technology Rourkela CERTIFICATE This is to certify that the thesis entitled, “Dynamic analysis of cantilever beam and its experimental validation” submitted by SUBHRANSU MOHAN SATPATHY and PRAVEEN DASH in partial fulfillment of the requirement for the award of Bachelor of Technology degree in Mechanical Engineering at National Institute of Technology, Rourkela is an authentic work carried out by him under my supervision and guidance. To the best of my knowledge, the matter embodied in the thesis has not been submitted to any other University/Institute for the award of any Degree or Diploma. Date: 12 May, 2014 Prof. H.ROY Dept. of Mechanical Engineering National Institute of Technology Rourkela 769008 2 ACKNOWLEDGEMENT I intend to express my profound gratitude and indebtedness to Prof. H.ROY, Department of Mechanical Engineering, NIT Rourkela for presenting the current topic and for their motivating guidance, positive criticism and valuable recommendation throughout the project work. Last but not least, my earnest appreciations to all our associates who have patiently extended all kinds of help for completing this undertaking. SUBHRANSU MOHAN SATPATHY (110ME0331) PRAVEEN DASH (110ME0289) Dept. of Mechanical Engineering National Institute of Technology Rourkela – 769008 3 INDEX SERIAL NO. CONTENTS PAGE NO. 1 INTRODUCTION 6 2 LITERATURE SURVEY 7 3 NUMERICAL FORMULATION 9 4 MODAL ANALYSIS 11 5 EXPERIMENTAL VALIDATION 22 6 CONCLUSION 31 4 FIGURES FIG NO.
    [Show full text]
  • Determination of Natural Frequencies Through Modal and Harmonic Analysis of Space Frame Race Car Chassis Based on ANSYS
    American Journal of Engineering and Applied Sciences Original Research Paper Determination of Natural Frequencies through Modal and Harmonic Analysis of Space Frame Race Car Chassis Based on ANSYS Mohammad Al Bukhari Marzuki, Mohammad Hadi Abd Halim and Abdul Razak Naina Mohamed Department of Mechanical Engineering, Sultan Azlan Shah Polytechnic, Behrang, Perak, Malaysia Article history Abstract: Space frame chassis the preferred choice of chassis design Received: 27-10-2014 due to its low cost, high strength, lightweight and safe qualities, which Revised: 10-02-2015 made it suitable for a single-seat race car application and an important Accepted: 11-07-2015 aspect in the construction of the space frame race car chassis. Key Corresponding Author: sections of a space frame race car chassis consist of front and main Mohammad Al Bukhari hoops, side impact protection and crush zone sub-frame. These sections Marzuki are pivotal in the safety aspect of the driver during emergency situation. Department of Mechanical This research introduces several methods of dynamic analysis to Engineering, Sultan Azlan Shah investigate the mode shape and natural frequencies in the chassis Polytechnic, Behrang, Perak, Malaysia structure. Two methods are mainly used in the study, modal analysis Email: [email protected] and harmonic analysis with both analyses are performed using Finite Element (FE) method through Finite Element Analysis (FEA) software packaged, ANSYS v13 APDL Mechanical. The study identified five mode shapes extracted using Block Lanczos method, all mode shapes vibrated at a frequency above 150 Hz with the characteristic of each mode shapes is further explained in this study. Amplitude vs.
    [Show full text]
  • Indirect Measurements of Bridge Vibrations As an Experimental Tool Supporting Periodic Inspections
    infrastructures Article Indirect Measurements of Bridge Vibrations as an Experimental Tool Supporting Periodic Inspections Stefano Ercolessi 1 , Giovanni Fabbrocino 1,2 and Carlo Rainieri 3,* 1 StreGa Lab, DiBT Department, University of Molise, 86100 Campobasso, Italy; [email protected] (S.E.); [email protected] (G.F.) 2 Secondary Branch of L’Aquila, Construction Technologies Institute, National Research Council of Italy, 67100 L’Aquila, Italy 3 Secondary Branch of Naples, Construction Technologies Institute, National Research Council of Italy, 80146 Naples, Italy * Correspondence: [email protected] Abstract: Recent collapses and malfunctions of European bridges threatened the service conditions of road networks and pointed out the need for robust procedures to mitigate the impact of mate- rial degradation and overloading of existing bridges. Condition assessment of bridges remains a challenging task, which could take advantage of cost-effective and reliable inspection strategies. The advances in sensors as well as Information and Communication Technologies (ICT) ensure a significant enhancement of the capabilities in recording and processing physical and mechanical data. The present paper focuses on the paradigm of indirect vibration measurements for modal parameter identification in operational conditions. It is very attractive because of the related opportunities of application of dynamic tests as a tool for periodic inspections while significantly mitigating their impact on the traffic flow. In this framework the instrumented vehicle acts as a dynamic measurement Citation: Ercolessi, S.; Fabbrocino, device for periodic inspections and provides valuable information on the structural response of the G.; Rainieri, C. Indirect Measurements of Bridge Vibrations as bridge at a low-cost.
    [Show full text]
  • Handout 7 (Undamped) Modal Analysis of MDOF Systems
    ME617 - Handout 7 (Undamped) Modal Analysis of MDOF Systems The governing equations of motion for a n-DOF linear mechanical system with viscous damping are: MU+DU+KU()tt =F () (1) where U,U,and U are the vectors of generalized displacement, velocity and acceleration, respectively; and F()t is the vector of generalized (external forces) acting on the system. M,D,K represent the matrices of inertia, viscous damping and stiffness coefficients, respectively1. The solution of Eq. (1) is uniquely determined once initial conditions are specified. That is, att =→ 0UUUU(0) =oo , (0) = (2) In most cases, i.e. conservative systems, the inertia and stiffness matrices are SYMMETRIC, i.e. MM= TT, KK= . The kinetic energy (T) and potential energy (V) in a conservative system are 11 TV==UMUTT, UKU (3) 22 1 The matrices are square with n-rows = n columns, while the vectors are n- rows. MEEN 617 – HD#7 Undamped Modal Analysis of MDOF systems. L. San Andrés © 2008 1 In addition, since T > 0, then M is a positive definite matrix2. If V >0, then K is a positive definite matrix. V=0 denotes the existence of a rigid body mode, and makes K a semi-positive matrix. In MDOF systems, a natural state implies a certain configuration of shape taken by the system during motion. Moreover a MDOF system does not possess only ONE natural state but a finite number of states known as natural modes of vibration. Depending on the initial conditions or external forcing excitation, the system can vibrate in any of these modes or a combination of them.
    [Show full text]
  • Modal Analysis, Dynamic Properties and Horizontal Stabilisation
    DOCTORAL T H E SIS Department of Civil, Environmental and Natural Resources Engineering Division of Industrialized and Sustainable Construction Timber Buildings and Horizontal Dynamic Properties Stabilisation of Analysis, Ida Edskär Modal ISSN 1402-1544 ISBN 978-91-7790-276-8 (print) ISBN 978-91-7790-277-5 (pdf) Modal Analysis, Dynamic Properties Luleå University of Technology 2018 and Horizontal Stabilisation of Timber Buildings Ida Edskär Timber Structures Modal Analysis, Dynamic Properties, and Horizontal Stabilisation of Timber Buildings Ida Edskär Luleå University of Technology Department of Civil, Environmental and Natural Resources Engineering Industrialized and Sustainable Construction Timber Structures Printed by Luleå University of Technology, Graphic Production 2018 ISSN: 1402-1544 ISBN: 978-91-7790-276-8 (print) ISBN: 978-91-7790-277-5 (electronic) Luleå 2018 www.ltu.se Expression of gratitude There are many people that have contributed to my journey to come where I am today. I would like to take the opportunity to thank you all, and especially the following persons: Helena Lidelöw, for all our long conversations and discussions. Impressed by your knowledge about matters big and small, which have really helped me. Without you, I would never have completed this. Lars Stehn, for always asking the right questions to challenge me. A great support during this time. Thomas Nord, for being part of the project and coming up with good input from an engineering perspective. Rune B. Abrahamsen, for your knowledge in timber engineering and the time in Lillehammer. It has been very important to me. Magne A. Bjertnæs, for your feedback, fruitful discussions and the time in Lillehammer.
    [Show full text]
  • Modal Analysis and Vibration Test for Quarter Wave Resonator for RAON
    19th Int. Conf. on RF Superconductivity SRF2019, Dresden, Germany JACoW Publishing ISBN: 978-3-95450-211-0 doi:10.18429/JACoW-SRF2019-TUP032 MODAL ANALYSIS AND VIBRATION TEST FOR QUARTER WAVE RESONATOR FOR RAON* Myung Ook Hyun†, Minki Lee, Youngkwon Kim, Hoechun Jung, Rare Isotope Science Project (RISP) / Institute of Basic Science (IBS), Daejeon, South Korea Abstract RESONANCE OF QWR SC The Rare Isotope Science Project (RISP) in the Institute CAVITYDURING COLD TEST of Basic Science (IBS), Korea, is developing and con- During cold test, there were some failures for RF phase structing the multi-purpose linear accelerator at the north control of QWR cavity due to unexpected disturbances. Af- side of Daejeon, South Korea. RISP accelerator (RAON) ter finishing cold test, we measured the vibration level on is composed of low-energy region (SCL3) and high-energy the several points of Munji SRF test facility. By repeating region (SCL2) [1]. Low-energy region is made with quar- turn-on and turn-off of all devices including general utili- ter-wave resonator (QWR) and half-wave resonator ties, we found that there were two main outer disturbances, (HWR) while high-energy region is made with single one came from the cold box of cryogenic system and the spoke resonator type-1 (SSR1) and type-2 (SSR2). This pa- other came from the water circulation pump connected to per presents the initial resonance issues of QWR supercon- the utility water supply line. Figures 2 and 3 show the dis- ducting (SC) cavity occurred during cold test and disturb- turbances from both vibration sources corresponding to the ance measurement in the Munji SRF test facility.
    [Show full text]
  • System Identification of Soil-Foundation Structure Systems by Means of Ambient Noise Records: the Case of Europroteas Model Structure in Euroseistest
    SYSTEM IDENTIFICATION OF SOIL-FOUNDATION STRUCTURE SYSTEMS BY MEANS OF AMBIENT NOISE RECORDS: THE CASE OF EUROPROTEAS MODEL STRUCTURE IN EUROSEISTEST Dimitris PITILAKIS1, Despina LAMPROU2, Maria MANAKOU3, Emmanuil ROVITHIS4, Anastasios ANASTASIADIS5, ABSTRACT In this paper we present the system identification of EuroProteas, a real-scale simplified model structure built in Euroseistest site in the framework of the European project “Seismic Engineering Research Infrastructures for European Synergies, SERIES”. EuroProteas design and construction involved a particularly stiff structure founded on soft soil, thus mobilization of strong soil-foundation-structure interaction (SFSI) effects is expected during structural oscillations. To this end, system identification is performed using various well-documented parametric and non-parametric techniques, regarding the estimation of the dynamic characteristics of the soil-foundation-structure system. System identification procedures are applied to estimate the modal parameters of the flexible-base structure, while the modal parameters of the fixed-base case are evaluated using a finite element model of the structure. By comparing the results, it is confirmed that the structure under study is subjected to strong SFSI effects. INTRODUCTION In order to estimate the dynamic response of a soil-foundation-structure system, its dynamic characteristics are required. The assumption of a fixed-base structure that is usually adopted in practice may be misleading, especially when the foundation soil is soft. There are many well-documented studies in literature for evaluating soil-foundation-structure interaction (SFSI) effects on structures’ dynamic response (Gazetas, 1991, Mylonakis et al., 2006). Even though such research efforts are very useful, the corresponding assumptions regarding soil conditions may deviate from those of an actual soil-foundation-structure system.
    [Show full text]