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1
Forsberg, Alexander, e Aras Wali. "Vibration reduction over junctions in buildings". Thesis, KTH, Marcus Wallenberg Laboratoriet MWL, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302260.
Testo completoAbstract (sommario):
Structure borne sound can travel multiple paths from one office to another and choosing to sound insulate a specific building element can be difficult since all the building elements are connected together and form a coupled system. The current approach by engineers when investigating transmission paths between spaces in a building is using a computer model and assuming that the junctions are firmly clamped or free. Standardized measuring methods includes a large amount of measuring points on each side of a junction and excitation over large areas. This study intends to investigate if it is possible to gain valuable information with a small amount of measuring points in a field measurement by comparing the data with an analytical model and a finite element model. The field measurement consisted of excitation from an impulse hammer from two excitation points and three accelerometers placed on each side of the junctions and on both sides of the separating wall. The measurement took place in a office building, with no information about the structure other than length, width and thickness of the elements.The reduction over the junctions varied with frequency and no general conclusion could be made about the transmission paths. The results showed high vibration reduction over the junction in low frequencies which then decreased in higher frequencies. Measurement results in low frequencies coincided with the analytical model, that vibration reduction is high over a junction for lighter separating walls in low frequencies and decrease quickly as frequency increases. Different results over each junction was obtained depending on excitation point, which indicates that there is flanking transmission along with the fact that it is a complex coupled system.Strukturburet ljud kan färdas flera olika vägar från ett kontor till ett annat och att ljudisolera en specifik vägg kan vara svårt då alla byggnadselement är ihopkopplade och skapar ett kopplat system. Den nuvarande metoden ingenjörer använder för att undersöka transmissionsvägar mellan rum är att skapa modeller i datorprogram där antaganden att byggnadselementen är fast inspända eller fritt upplagda är gjorda. Standardiserade mätmetoder använder sig av en stor mängd mätpunkter på båda sidor om knutpunkterna och excitationer över stora ytor. Den här studien avser att undersöka möjligheten att erhålla värdefull information med ett fåtal mätpunkter i en fältmätning genom att jämföra den samlade mätdatan med en analytisk modell och en FEM modell. Fältmätningen består av excitation med en impulshammare i två excitationspunkter och tre accelerometrar på vardera sida om knutpunkterna och båda sidor om skiljeväggen. Mätningen utfördes i en kontorsbyggnad, utan någon information om strukturen förutom längd, bredd och tjocklek på byggnadselementen.Reduktionen över knutpunkterna varierade i frekvens och inga generella slutsatser kunde göras angående transmissionsvägar. Resultaten visade hög reduktion i vibrationsskillnad över knutpunkterna i låga frekvenser vilket minskade med ökad frekvens. Mätningsresultaten stämde överens med den analytiska modellen i låga frekvenser, med avseende på att reduktionen över knutpunkter med lätt skiljevägg är hög i låga frekvenser och avtar med ökad frekvens. Resultaten över knutpunkterna var beroende på val av excitationspunkt vilket indikerar att mätresultaten innehåller flankerande transmissioner och att det är ett komplext kopplat system.
2
Galbrun, Laurent. "Vibration transmission in timber-framed buildings". Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/337.
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3
Edalath, Sanooj Sadique. "Fuzzy Logic Seismic Vibration Control of Buildings". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1335462916.
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4
Boffa, John. "Model Reduction of Large Structural Systems for Active Vibration Control". University of Technology, Sydney. Faculty of Engineering, 2006. http://hdl.handle.net/2100/338.
Testo completoAbstract (sommario):
This thesis studies the applicability of the Dynamic model reduction method that is used for direct plant order reduction in the active vibration control of large and flexible structures. A comparison of the performances between the reduced models produced by the Dynamic model reduction method and those obtained by other common model reduction methods such as the Guyan method, and the Mode-displacement method have been carried out. By using a full analytical model of a twenty storey building as the reference, each three degrees of freedom model was compared by computer simulation. The open-loop frequency response simulation, open-loop earthquake simulation, and the closed-loop earthquake simulation were all used to initially evaluate the reduced models. The accuracy of the frequency responses was assessed with sinusoidal applied forces, and for the closed-loop dynamic analysis, an active mass damper at the top storey and a recorded earthquake excitation was used. When compared with the simulation results of the Guyan method, the Dynamic method has many advantages, especially in terms of its accuracy at the high frequency range. The Mode-displacement method produces reduced models that are good for dynamic analysis of open-loop systems, but it was found to be inconvenient for use in active control. Finally, the Dynamic model reduction method and Guyan method were compared using experimental test results. A 2.5m tall building model with 20 floors was used as the plant, with a linear motor installed at the top storey for the purposes of active-damping. Although the results of simulations would suggest that both models perform sufficiently, experimental testing proved that only the Dynamic model performs adequately for this specific application of active control. The problem associated with most model reduction methods, such as the Guyan, is that they are based on full-order models that were derived from the linear elastic theory. The versatility of the Dynamic model reduction method is such that it provides the option of obtaining system parameters directly from experiment, not just from theory. The experimental procedure ensures that the Dynamic model reduction method forms an accurate description of the real system dynamics. The applicability of this method for obtaining low-order plant models was demonstrated through real-time active control testing of the model structure, while it was subject to a sinusoidal excitation. The tests have shown that the Dynamic model reduction method can be used as an alternative approach for the model reduction of structural systems for the purpose of active vibration control.
5
Boffa, John. "Model reduction of large structural systems for active vibration control /". Electronic version, 2002. http://adt.lib.uts.edu.au/public/adt-NTSM20060317.113054/index.html.
Testo completo
6
Dominguez, Morales Martha. "Fundamental period of vibration for reinforced concrete buildings". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ58450.pdf.
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7
Zhou, Li. "Vibration control of buildings using smart magnetorheological dampers /". View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202002%20ZHOU.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 163-177). Also available in electronic version. Access restricted to campus users.
8
Wang, Yi. "Damage assessment in asymmetric buildings using vibration techniques". Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/120475/1/Yi_Wang_Thesis.pdf.
Testo completoAbstract (sommario):
This research presents a step forward in the area of structural health monitoring by developing the scientific basis for a method to detect and locate damage in asymmetric building structures accurately and efficiently. The method is based on the changes in the vibration characteristics of asymmetric buildings such as natural frequencies and associated mode shapes. The thesis first investigated the difference in vibration behavior between symmetric and asymmetric buildings and compared the capability of different damage detection methods that uses the vibration characteristics. Then a modified method (MMSE) and an improved method (MCA-DI) were proposed based on the comparative study and verified through experimental testing of a laboratory scale asymmetric setback structure model.
9
Xu, Y. L. (You Lin) 1952. "Vibration control of wind-excited tall/slender structures". Phd thesis, School of Civil and Mining Engineering, 1991. http://hdl.handle.net/2123/9458.
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10
Howarth, Henrietta Victoria Carmel. "Annoyance caused by railway vibration and noise in buildings". Thesis, University of Southampton, 1989. https://eprints.soton.ac.uk/52250/.
Testo completoAbstract (sommario):
This thesis is concerned with the annoyance caused by railway-induced building vibration and railway noise. A review of previous studies was conducted to examine current knowledge. The review enabled identification of areas in which there was insufficient information on which to base a prediction of the reaction to railway vibration and noise in buildings. Deficiencies in current knowledge formed the basis of a programme of experimental work which was conducted to investigate how the annoyance produced by railway-induced building vibration is affected by the number of trains, the vibration magnitude, the vibration frequency, the direction of vibration and the presence of noise. Two laboratory experiments were concerned with how annoyance caused by railway-induced building vibration depends on the magnitude of vibration and on how often trains pass. A trade-off was determined between the number of trains and the vibration magnitude which indicated a fourth power relation between magnitude and duration. The relation supports the use of the vibration dose value as a method of vibration assessment. Two further experiments were conducted to determine the subjective equivalence of noise and vibration and to investigate the interaction and combined effects of the two stimuli. The results suggest that vibration does not influence the assessment of noise but that the assessment of vibration can be increased or reduced by the presence of noise, depending on the relative magnitudes of the vibration and noise. A fifth experiment was performed to investigate the influence on annoyance of vibration frequency, vibration magnitude and vibration direction. Vibration frequency weightings were determined to describe subjective response to whole-body vibration at low magnitudes such as occurs in buildings. The results indicate that the weightings in British Standard 6841 (1987) provide a reasonable approximation to the frequency dependence of response to whole-body vibration at low magnitudes. In the final experiment the previous findings were combined to provide a general method of predicting the relative annoyance from complex conditions of railway vibration and noise. The method was shown to provide a more accurate prediction of the relative annoyance from railway vibration and noise than methods based on the influence of noise or vibration alone.
11
Talbot, James P. "On the performance of base-isolated buildings : a generic model". Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/244274.
Testo completoAbstract (sommario):
Ground-borne vibration has existed ever since the development of urban road and rail networks. Vibration generated by the moving traffic propagates through the ground and into buildings, resulting in unacceptable levels of internal noise and vibration. A common solution to this increasingly significant problem is the base-isolation of buildings by incorporating vibration isolation bearings between the buildings and their foundations. This technique has been employed for over forty years but the exact performance of base isolation remains uncertain. This dissertation is concerned with the development of a generic computational model; generic in that it accounts for the essential dynamic behaviour of a typical base-isolated building in order to make predictions of isolation performance. The model is a linear one, formulated in the frequency domain, and consists of a two-dimensional portal-frame model of a building coupled to a three-dimensional boundary-element model of a piled-foundation. Both components of the model achieve computational efficiency by assuming they are infinitely long and using periodic structure theory. The development of the model is described systematically, from the modelling of a building and its isolation bearings to that of its foundation. The majority of the work is concerned with the piled-foundation model, which is comprehensive in that it accounts for the vertical, horizontal and rotational motion of the pile heads due to both direct pile-head loading and interaction through wave propagation in the surrounding soil. It is shown that this level of detail is important in the prediction of base isolation efficiency. A key question facing designers is not only how but on what basis base isolation should be assessed, since fundamental problems exist with the existing measures of isolation performance. Power flow analysis is explored and the concept of power flow insertion gain, based on the total mean vibrational power flow entering a building, is introduced as a useful measure of isolation performance. This is shown to offer clear benefits by providing a single measure of performance that is suitable for design purposes. Finally, the development of a prototype force-sensitive vibration isolation bearing is described as a contribution to verifying base-isolation theory with experiments.
12
Rafezy, Behzad. "Global vibration analysis of symmetric and asymmetric high rise buildings". Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55960/.
Testo completoAbstract (sommario):
This thesis presents two global analysis approaches to the calculation of the natural frequencies of high rise buildings. The structures are proportional and their component members are repeated at each storey level unless there is a step change of properties. Within this scope many geometric configurations can be encompassed, ranging from uniform structures with doubly symmetric floor plans to doubly asymmetric ones comprising plane frame and wall structures running in two orthogonal directions. The first method utilises a continuum element approach in which the structure is divided into segments by cutting through the structure horizontally at those storey levels corresponding to changes in storey properties. A typical segment is then replaced by an appropriate substitute beam that has uniformly distributed mass and stiffness. Subsequently, the governing differential equations of the substitute beam are formulated using the continuum approach and posed in the form of a dynamic member stiffness matrix that is exact to small deflection theory. Since the formulation allows for the distributed mass and stiffness of the member, it necessitates the solution of a transcendental eigenvalue problem. The required natural frequencies are thus determined using a cantilever model in conjunction with the Wittrick-Williams algorithm, which ensures that no natural frequencies can be missed. In addition, a two step process has been developed for certain asymmetric structures in which the natural frequencies corresponding to coupled motion between the planes of vibration can be obtained from the equivalent uncoupled ones through a simple cubic relationship. This enables coupled, three-dimensional vibration problems to be solved very efficiently using a two dimensional approach. The second method utilises the Principle of Multiples which, when applicable, enables any frame, regardless of the number of storeys or bays, to be simplified to an equivalent one bay frame, that has precisely the same natural frequencies. If the original frame does not fully satisfy the Principle, the same process can still be utilised, but the resulting substitute frame will yield approximate frequencies, although they will normally be acceptable to engineering accuracy. Like the first method, it can also be used for the vibration analysis of asymmetric, three-dimensional frame and wall-frame structures in a two-step procedure. First the analogous uncoupled system is analysed using substitute frames, then the relationship between the uncoupled and coupled responses is imposed through a cubic equation. Both of the above methods assume rigid floor diaphragms and require a knowledge of the building's static eccentricity at each storey level. The current methods of calculating this are cumbersome and even the definitions are open to dispute. A practical method of calculation is therefore presented and a small parametric study enables recommendations to be made. Overall, the proposed methods require little effort, offer clear and concise output and can sometimes yield solutions of sufficient accuracy for definitive checks, but more usually provide engineering accuracy for intermediate checks during tasks such as scheme development or remedial work. This claim is supported by the results of extensive parametric studies undertaken for this thesis. In all examples, the results from the proposed methods have been compared with the results of a full finite element analysis of the original structure obtained using the vibration programme ETABS. The exercise confirms that the proposed methods can yield results of sufficient accuracy for engineering calculations.
13
Steel, J. A. "Structural vibration transmission in framed buildings using statistical energy analysis". Thesis, Heriot-Watt University, 1990. http://hdl.handle.net/10399/889.
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14
Cryer, David Patrick. "Modelling of vibration in buildings with application to base isolation". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336535.
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15
Ming, Ruisen. "The measurement of structural wave intensity applied to buildings". Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1470.
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16
Jacobsen, Erica Dawn. "Forced Vibration Testing and Analysis of Pre- and Post- Retrofit Buildings". DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/531.
Testo completoAbstract (sommario):
ABSTRACT
Forced Vibration Testing and Analysis of Pre- and Post- Retrofit Buildings
Erica Dawn Jacobsen
The primary goal of the thesis was to detect the retrofit through vibration testing of both buildings. The secondary goal focused on correctly identifying the behavior of the building through FVT, comparing that behavior to computational model predictions, and determining the necessary level of detail to include in the computational modeling. Forced vibration testing (FVT) of two stiff-wall/flexible-diaphragm buildings yielded natural frequencies and mode shapes for the two buildings. The buildings were nearly identical with the exception that one had been retrofitted. Both buildings were comprised of concrete shearwalls and steel moment frames in the north/south direction and moment frames in the east/west direction. The retrofit strengthened the moment connections and added braces to the perimeter walls in the east/west direction.
The natural frequencies were found through FVT by setting a 30-lb shaker on the roof of both buildings and sweeping through a range of frequencies in both the east/west and north/south directions. Accelerometers were placed on the building to detect the accelerations. The peaks on the Fast Fourier Transform (FFT) graphs indicated the frequencies at which the structure resonated. Mode shapes were tested for by placing the shaker in a position ideal for exciting the mode and setting the shaker to the natural frequency detected from the FFT graphs. The accelerometers were placed around the roof of the building to record the mode shape.
After testing, computational models were created to determine if the models could accurately predict the frequencies and mode shapes of the buildings as well as the effect of the retrofit. A series of increasingly complex computational models, ranging from hand calculations to 3D models, were created to determine the level of detail necessary to predict the building behavior. Natural frequencies were the primary criteria used to determine whether the model accurately predicted the building behavior. The mid-diaphragm deflection and base shear from spectral analysis were the final criteria used to compare these select models.
It was determined that in order to properly capture the modal behavior of the building, the sawtooth framing, major beams, and the lateral-force-resisting-system (LFRS) must be modeled. Though the mode shape of the building is dominated by the flexible diaphragm, the LFRS is necessary to model to accurately predict both the natural frequency of the building as well as the diaphragm deflection.
17
Anthony, David. "Movers and shakers : the affects of vibrations on historic structures". Virtual Press, 1997. http://liblink.bsu.edu/uhtbin/catkey/1041912.
Testo completoAbstract (sommario):
Preservationists and historic sites managers need to be aware of the affects of excess man-made vibrations on historic structures. The purpose of this creative project is to examine those affects and identify some methods to mitigate them. To write this project, it was necessary to search through available literature identifying past research and studies on this subject. Research was culled from various sources examining the affects of vibrations on new and historic structures and are presented here in one volume.The affects of vibrations on historic structures is not a subject that is well represented in preservation or structural engineering literature. The information currently available is scattered through various sources. Thus, there is the lack of a single reference examining the affects of vibrations on historic structures. This project is meant to be used as a reference for historic preservationists, house museum curators, and historic sites managers who seek information about vibration effects and possible solutions to their vibration problem.Department of Architecture
18
Bolter, J. D. "Active damping of framework vibrations". Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382018.
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揚毅 e Ngai Yeung. "Viscous-damping walls for controlling wind-induced vibrations in buildings". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31242637.
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20
Al, Haddad Aiham Emil. "Wind-induced Vibration Control of Tall Timber Buildings : Improving the dynamic response of a 22-storey timber building". Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-57005.
Testo completoAbstract (sommario):
Plans for construction of the tallest residential timber building has driven the Technical Research Institute of Sweden (SP), Linnaeus University, Växjö and more than ten interested companies to determine an appropriate design for the structure. This thesis presents a part of ongoing research regarding wind-induced vibration control to meet serviceability limit state (SLS) requirements. A parametric study was conducted on a 22-storey timber building with a CLT shear wall system utilizing mass, stiffness and damping as the main parameters in the dynamic domain. Results were assessed according to the Swedish Annex EKS 10 and Eurocode against ISO 10137 and ISO 6897 requirements. Increasing mass, stiffness and/or damping has a favorable impact. Combination scenarios present potential solutions for suppressing wind-induced vibrations as a result of higher efficiency in low-increased levels of mass and damping.
21
Hafeez, Ghazanfarah. "Dynamic Characteristics of Light-frame Wood Buildings". Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36223.
Testo completoAbstract (sommario):
This research project deals with dynamic field testing of light-frame wood buildings with wood based shear walls. The primary objective of the investigation is to evaluate the code formula for estimating light wood frame building’s fundamental period, through intensive field testing and numerical modelling. The project also aims to propose an alternative simplified rational approach where applicable. The thesis provides insight to the ambient vibration testing procedures of light-frame wood buildings and explains the protocol adopted for the current research program.
Ambient vibration (AV) field tests were conducted on several multi-storey wood and beam-and-post buildings in Canada. Modal parameters of measured buildings, such as natural frequency, mode shapes and equivalent structural damping were obtained from Frequency Domain (FD) analysis of ambient motion records.
Experimental and numerical investigations were performed to evaluate the effect of non-structural components, and the connectivity between firewall-separated buildings, on dynamic properties of light-frame wood buildings. The study provides a reliable expression for building period estimate based on field testing and numerical modeling.
22
Ticona, A. M., M. A. Rosales e J. D. Orihuela. "Correction coefficients of distortion and vibration period for buildings due to soil-structure interaction". OP Publishing Ltd, 2020. http://hdl.handle.net/10757/656571.
Testo completoAbstract (sommario):
The present research analyzed the influence of the soil structure interaction (SSI) in buildings, varying geotechnical parameters and height, considering 3 international codes. The responses obtained from the structures taking into account the SSI, were compared with the responses of fixed-base buildings, being the main control variables: the period and the drift. It was determined that the estimated range in which the period of the structure increases is from 30 to 98%, demonstrating the influence of considering soil flexibility. Due to the variability of the responses obtained, an adjustment factor is proposed to predict said amplification of the control variables, depending on the height of the building and the ground.
23
Alajlouni, Sa'ed Ahmad. "Energy-based Footstep Localization using Floor Vibration Measurements from Accelerometers". Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/103466.
Testo completoAbstract (sommario):
This work addresses the problem of localizing an impact in a dispersive medium (waveguide) using a network of vibration sensors (accelerometers), distributed at various locations in the waveguide, measuring (and detecting the arrival of) the impact-generated seismic wave. In particular, the last part of this document focuses on the problem of localizing footsteps using underfloor accelerometers.
The author believes the outcomes of this work pave the way for realizing real-time indoor occupant tracking using underfloor accelerometers; a system that is tamper-proof and non-intrusive compared to occupant tracking systems that rely on video image processing.
A dispersive waveguide (e.g., a floor) causes the impact-generated wave to distort with the traveled distance and renders conventional time of flight localization methods inaccurate. Therefore, this work focuses on laying the foundation of a new alternative approach to impact localization in dispersive waveguides. In this document, localization algorithms, including wave-signal detection and signal processing, are developed utilizing the fact that the generated wave's energy is attenuated with the traveled distance. The proposed localization algorithms were evaluated using simulations and experiments of hammer impacts, in addition to occupant tracking experiments. The experiments were carried out on an instrumented floor section inside a smart building.
As will be explained in this document, energy-based localization will turn out to be computationally cheap and more accurate than conventional time of flight techniques.PHD
24
Al-Rumaih, Wail Saad. "A novel tuned visco-elastic damper for floor vibration abatement". Dayton, Ohio : University of Dayton, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1245387294.
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Erisen, Zuhtu Eren. "Frequency Domain Optimization Of Dry Friction Dampers Used For Earthquake Vibration Damping Of Buildings". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614134/index.pdf.
Testo completoAbstract (sommario):
There are many active and passive vibration control techniques to reduce the effect of energy on structures which emerges during an earthquake and reduce the displacement of buildings that is caused by ground acceleration. Main advantage of passive vibration control techniques over active vibration control techniques isno external power or a sensor is required for passive vibration control devices (PVCDs) and it results in lower installation and maintenance costs. However, PVCDs require a predefined optimum damping ratio and optimum damping distribution along the structure since they are not adaptive to changing ground acceleration values. During the design of the PVCDs numerous factors such as building properties and earthquake characteristics should be considered. Dry friction damper is an example of PVCD and has an extensive usage in many different fields due to its high energy damping capacity with low cost and ease of installation. In this thesis, damping of seismic energy at buildings with dry friction dampers is investigated and a new optimization method is developed in frequency domain by employing Describing Function Method (DFM) which reduces the computational effort compared to the time domain and finite element solutions drastically. The accuracy and verification of the presented method is investigated by comparing the frequency domain results with time marching solutions. Furthermore, damper placement and slip forces on the dampers are optimized for single and multi-story buildings equipped with dry friction dampers by utilizing the developed method.
26
Cook, Christopher R. "Methods to improve the vibration characteristics of joist supported floor systems". Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42157.
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Andreozzi, Michele. "Seismic protection of buildings of historical/cultural interest through the use of vibrating barriers". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Cerca il testo completoAbstract (sommario):
Recent earthquake events pointed out the problematic of protecting existing buildings from the catastrophic effects of earthquakes. The current strategies for vibration are successfully employed in the design of new structures; on the other hand, they are rarely used for protecting existing buildings, because they generally require substantial alteration of the original structure. In this thesis, a novel device called vibrating barrier, (ViBa), is implemented for the seismic protection of an historical building: the Bell Tower of the Messina Cathedral. This device is able to reduce the dynamic response of a target building without being physically connected to it. The dynamic behaviour of the system has been studied through the construction of a detailed FE Model that allowed to derive the response of the structure and to study the existing influences between the buildings and the effect of the soil. Hence, a simplified mathematical model has been constructed, and the pertinent parameters have been computed by the employment of an Identification Process. Moreover, the mechanical parameters of the ViBa have been derived through an Optimization Process in order to reduce a selected response parameter of the bell tower, under an input ground motion modelled as Gaussian Stochastic Process compatible with the Messina response spectrum. Hence, parametric analyses have been carried out in order to investigate the influence of the mass of the device on the efficiency. Spectrum-compatible artificial accelerograms have been generated and a significant average reduction of the maximum displacements of 25% has been achieved, together with a decrease of 40% of the shear forces in the bell tower. Due to large masses involved, alternative solutions have been proposed against the problems related to a real-life implementation of the device, and the beneficial effects given by the coupling of the ViBa with a set of mechanical inerters have been demonstrated.
28
Malushte, Sanjeev R. "Seismic response of structures with Coulomb damping". Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54235.
Testo completoAbstract (sommario):
The usefulness of Coulomb (friction) damping in earthquake-resistant design of structures is examined by studying the seismic response characteristics of structures with various arrangements of sliding interfaces. First, three basic arrangements are studied for their effectiveness in reducing lateral displacements of the supporting frame, accelerations of the floor slab and the resulting secondary floor spectra. These are: (1) slab sliding system which has the sliding interface between the floor slab and the supporting frame, (2) double sliding system which consists of sliding interfaces at both top and bottom interfaces (a combination of slab sliding and base sliding), and (3) spring-assisted slab sliding system which is a slab sliding system aided by lateral springs attached to the columns to resist excessive sliding displacement of the slab. The responses are obtained for structures with different frequencies and are presented in response spectrum form. The isolation characteristics of one slab sliding system are compared with those of the base sliding and hysteretic systems. Non-dimensional design parameters defined in terms of the corresponding elastic design spectra are introduced for design purposes and for a consistent presentation of the results. Methods for predicting the important response quantities using the non-dimensional parameters are discussed and their applicability is evaluated.
Next, the response of a simple slab sliding arrangement to simultaneous horizontal and vertical ground motion input is studied to see the effects of the vertical excitation on the isolation efficiency of that arrangement. Finally the suitability of adopting such sliding arrangements in multi-story structures is also examined. The seismic responses of multi-story structures with floor slabs sliding at different story levels are obtained and compared with the response of non-sliding structure and base sliding to examine the effectiveness of such sliding arrangement.Ph. D.
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Goncalves, Rafael dos Santos. "Applications of Vibration-Based Occupant Inference in Frailty Diagnosis through Passive, In-Situ Gait Monitoring". Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104868.
Testo completoAbstract (sommario):
This work demonstrates an application of Vibration-Based Occupant Inference (VBOI) in frailty analysis. The rise of both Internet-of-Things (IoT) and VBOI provide new techniques to perform gait analysis via footstep-induced vibration which can be analyzed for early detection of human frailty. Thus, this work provides an application of VBOI to passively track gait parameters (e.g., gait speed) using floor-mounted accelerometers as opposed to using a manual chronometer as it is commonly performed by healthcare professionals.
The first part of this thesis describes the techniques used for footstep detection by measuring the power of the footstep-generated vibration waves. The extraction of temporal gait parameters from consecutive footsteps can then be used to estimate temporal features such as cadence and stride time variation.
VBOI provides many algorithms to accurately detect when a human-induced vibration event happened, however, spatial information is also needed for many gait parameters used in frailty diagnosis. Detecting where an event happened is a complicated problem because footsteps waves travel and decay in different ways according to the medium (floor system), the number of people walking, and even the walking speed. Therefore, the second part of this work will utilize an energy-based approach of footstep localization in which it is assumed that footstep waves decay exponentially as they travel across the medium. The results from this approach are then used to calculate spatial and tempo-spatial parameters.
The main goal of this study is to understand the applicability of VBOI algorithms in gait analysis for frailty detection in a healthcare setting.Master of Science
Human frailty is responsible for one of the highest healthcare costs and the death of many people every year. Although anyone suffering from frailty has a higher chance of death, it is particularly dangerous for the elderly population and for those suffering from other comorbidities. Diagnosing frailty is hard because it usually happens slowly over time. However, it has been shown that changes in some walking parameters (such as gait speed) can be an early indication of frailty. Many technologies have been created in order to track gait parameters, many of which either require expensive equipment (e.g., force plates) or the use of wearable devices, which can introduce privacy concerns. It has been proposed in the literature that Vibration-Based Occupant Inference (VBOI) techniques could be used in healthcare applications. Such algorithms measure footstep-induced vibration waves in order to detect and track footsteps. This system can provide several advantages in frailty analysis because of its affordability, ease of use, and little impact on patients' privacy. Therefore, the aim of this study is to understand the applicability of VBOI algorithms in gait analysis for frailty detection to be used in a healthcare setting. This thesis will proceed as follows: 1- The demonstration of an energy-based footstep detection and localization algorithm in VBOI. 2 - The application of such algorithms for gait parameters extraction with simulated frail walkers. 3 - Finally, an analysis of the proposed VBOI techniques for deployment in a real hospital setting.
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Azimi, Mohsen. "Design of Structural Vibration Control Using Smart Materials and Devices for Earthquake-Resistant and Resilient Buildings". Thesis, North Dakota State University, 2017. https://hdl.handle.net/10365/28588.
Testo completoAbstract (sommario):
Major earthquakes in recent years have highlighted the big concern of modern seismic design concept for the resilience of buildings. The overall goals of this thesis aim to design structural vibration control using smart materials and devices and to elucidate the factors determining their robustness, feasibility, and adaptability for earthquake-resistant and resilient buildings. The study mainly includes a) integrated wavelet-based vibration control with damage detection; b) shape memory alloy to eliminate the residual deformations; c) a mass damper for highly irregular tall buildings; and d) soil-structure interaction effects on the buildings. The robustness, feasibility, and adaptability of these proposed studies for earthquake-resistant and resilient buildings are evaluated using various performance measures. The findings of the study reveal that the structural vibration control strategies could advance the current-of-art knowledge in seismic risk mitigation as well as high system adaptability.
31
Kessler, Ellis Carl. "A Physically Informed Data-Driven Approach to Analyze Human Induced Vibration in Civil Structures". Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/104020.
Testo completoAbstract (sommario):
With the rise of the Internet of Things (IoT) and smart buildings, new algorithms are being developed to understand how occupants are interacting with buildings via structural vibration measurements. These vibration-based occupant inference algorithms (VBOI) have been developed to localize footsteps within a building, to classify occupants, and to monitor occupant health. This dissertation will present a three-stage journey proposing a path forward for VBOI research based on physically informed data-driven models of structural dynamical systems.
The first part of this dissertation presents a method for extracting temporal gait parameters via underfloor accelerometers. The time between an occupant's consecutive steps can be measured with only structural vibration measurements with a similar accuracy to current gait analysis tools such as force plates and in-shoe pressure sensors. The benefit of this, and other VBOI gait analysis algorithms, is in their ease of use. Gait analysis is currently limited to a clinical setting with specialized measurement systems, however VBOI gait analysis provides the ability to bring gait analysis to any building.
VBOI algorithms often make some simplifying assumptions about the dynamics of the building in which they operate. Through a calibration procedure, many VBOI algorithms can learn some system parameters. However, as demonstrated in the second part of this dissertation, some commonly made assumptions oversimplify phenomena present in civil structures such as: attenuation, reflections, and dispersion. A series of experimental and theoretical investigations show that three common assumptions made in VBOI algorithms are unable to account for at least one of these phenomena, leading to algorithms which are more accurate under certain conditions.
The final part of this dissertation introduces a physically informed data-driven modelling technique which could be used in VBOI to create a more complete model of a building. Continuous residue interpolation (CRI) takes FRF measurements at a discrete number of testing locations, and creates a predictive model with continuous spatial resolution. The fitted CRI model can be used to simulate the response at any location to an input at any other location. An example of using CRI for VBOI localization is shown.Doctor of Philosophy
Vibration-based occupant inference (VBOI) algorithms are an emerging area of research in smart buildings instrumented with vibration sensors. These algorithms use vibration measurements of the building's structure to learn something about the occupants inside the building. For example the vibration of a floor in response to a person's footstep could be used to estimate where that person is without the need for any line-of-sight sensors like cameras or motion sensors. The storyline of this dissertation will make three stops: The first is the demonstration of a VBOI algorithm for monitoring occupant health. The second is an investigation of some assumptions commonly made while developing VBOI algorithms, seeking to shed light on when they lead to accurate results and when they should be used with caution. The third, and final, is the development of a data-driven modelling method which uses knowledge about how systems vibrate to build as detailed a model of the system as possible. Current VBOI algorithms have demonstrated the ability to accurately infer a range of information about occupants through vibration measurements. This is shown with a varied literature of localization algorithms, as well as a growing number of algorithms for performing gait analysis. Gait analysis is the study of how people walk, and its correlation to their health. The vibration-based gait analysis procedure in this work demonstrates extracting distributions of temporal gait parameters, like the time between steps. However, many current VBOI algorithms make significant simplifying assumptions about the dynamics of civil structures. Experimental and theoretical investigations of some of these assumptions show that while all assumptions are accurate in certain situations, the dynamics of civil structures are too complex to be completely captured by these simplified models. The proposed path forward for VBOI algorithms is to employ more sophisticated data-drive modelling techniques. Data-driven models use measurements from the system to build a model of how the system would respond to new inputs. The final part of this dissertation is the development of a novel data-driven modelling technique that could be useful for VBOI. The new method, continuous residue interpolation (CRI) uses knowledge of how systems vibrate to build a model of a vibrating system, not only at the locations which were measured, but over the whole system. This allows a relatively small amount of testing to be used to create a model of the entire system, which can in turn be used for VBOI algorithms.
32
Moragaspitiya, Himenshu Nalindrajith. "Interactive axial shortening of columns and walls in high rise buildings". Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48026/1/Himenshu_Moragaspitiya_Thesis.pdf.
Testo completoAbstract (sommario):
Concrete is commonly used as a primary construction material for tall building construction. Load bearing components such as columns and walls in concrete buildings are subjected to instantaneous and long term axial shortening caused by the time dependent effects of "shrinkage", "creep" and "elastic" deformations. Reinforcing steel content, variable concrete modulus, volume to surface area ratio of the elements and environmental conditions govern axial shortening. The impact of differential axial shortening among columns and core shear walls escalate with increasing building height. Differential axial shortening of gravity loaded elements in geometrically complex and irregular buildings result in permanent distortion and deflection of the structural frame which have a significant impact on building envelopes, building services, secondary systems and the life time serviceability and performance of a building. Existing numerical methods commonly used in design to quantify axial shortening are mainly based on elastic analytical techniques and therefore unable to capture the complexity of non-linear time dependent effect. Ambient measurements of axial shortening using vibrating wire, external mechanical strain, and electronic strain gauges are methods that are available to verify pre-estimated values from the design stage. Installing these gauges permanently embedded in or on the surface of concrete components for continuous measurements during and after construction with adequate protection is uneconomical, inconvenient and unreliable. Therefore such methods are rarely if ever used in actual practice of building construction. This research project has developed a rigorous numerical procedure that encompasses linear and non-linear time dependent phenomena for prediction of axial shortening of reinforced concrete structural components at design stage. This procedure takes into consideration (i) construction sequence, (ii) time varying values of Young's Modulus of reinforced concrete and (iii) creep and shrinkage models that account for variability resulting from environmental effects. The capabilities of the procedure are illustrated through examples. In order to update previous predictions of axial shortening during the construction and service stages of the building, this research has also developed a vibration based procedure using ambient measurements. This procedure takes into consideration the changes in vibration characteristic of structure during and after construction. The application of this procedure is illustrated through numerical examples which also highlight the features. The vibration based procedure can also be used as a tool to assess structural health/performance of key structural components in the building during construction and service life.
33
Demirok, Emel. "3d-fe Model Field-calibration And Rating Studies On Existing R/c Buildings". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607223/index.pdf.
Testo completoAbstract (sommario):
Dynamic instrumentation and a series of ambient vibration tests were performed on a four storey strengthened R/C building within the scope of this study. Traffic load and wind load were accepted as natural dynamic loads and the vibrations were recorded by sensitive accelerometers.For that study, 12 uniaxial, 1 triaxial accelerometers and a 15 channel data logger system were used.
Four sets of dynamic measurements were recorded over a period of 6 months. Recorded readings were analyzed using UPC, PC and CVA algorithms and Artemis software. The natural freqeuncies, mode shape of the tested building were determined. The experimental results were compared against each other. A 3D-FE model of the building was prepared and analytical results were also compared against experimental results.The calibration (updating) of the analytical model was carried out using the experimentally obtained mode shapes and freqeunices.
The results of the study indicate that first few mode shapes and freqeuncies of the building can be obtained successfully within zero to 10 Hz range using ambient monitoring. Field calibrated FE models can effectively simulate the first translational and torsional modes of the building. Calibration studies indicate that the upper floor is more flexible than the nominal model and there are weaknesses between the shear wall and roof slab connections.
34
Nasser-Barakat, Fatima. "Automatic modal variation tracking via a filter-free random decrement technique application to ambient vibration recordings on high-rise buildings". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT044/document.
Testo completoAbstract (sommario):
Cette thèse propose une nouvelle approche pour surveiller automatiquementles variations des fréquences et des taux d’amortissement des batiments de grande hauteursoumis à des vibrations ambiantes. L’approche vise à relever simultanément avec les défissuivants: signaux multi-composants enregistrées sur les bâtiments mentionnés ci-dessusavec des réponses impulsionnelles ayant des modes de fréquences rapprochées, des amplitudesfaibles, exponentielles et amorties noyées dans des bruits additifs élevés. La méthoderepose sur l’application de la technique de décrément aléatoire directement sur le signal multicomposantece qui conduit à l’estimation d’une signature de décrément aléatoire multi-modeéquivalente à la réponse impulsionnelle de système. Pour caractériser une telle signature,nous proposons un modèle de signal basé sur la structure physique du bâtiment à partir delaquelle les paramètres modaux peuvent être estimés. Dans le but d’avoir une estimationnon biaisée, nous proposons d’utiliser une méthode itérative sur la base d’une estimation dumaximum de vraisemblance optimisé par une technique de recuit simulé. Afin d’initialiserles paramètres de ce dernier, une première étape est conçu qui peut être considéré commeun estimateur indépendant des paramètres modaux. L’originalité de cette étape réside danssa capacité à définir automatiquement le nombre de modes de la signature estimé grâce àl’utilisation des propriétés statistiques d’un spectre estimé par une transformée de Fourier.Les paramètres modaux estimés par l’étape d’initialisation sont finalement affinés par l’étaped’estimation du maximum de vraisemblance. Celui-ci réduit le biais de l’estimation et donnedes résultats plus fiables et plus robustes. Toutes ces étapes sont définies de manière à être enmesure de surveiller automatiquement l’état de santé d’un bâtiment par l’intermédiaire d’unsuivi long terme en temps réel des variations modales dans le temps sans que l’interventionde l’utilisateur soit nécessaire. En outre, l’approche proposée a accordé une attention touteparticulière à l’estimation automatique du paramètre modal les plus problématique, c’està-dire, le taux d’amortissement. Ces deux caractéristiques sont des atouts originaux parrapport aux techniques existantes. L’adaptabilité et la fonctionnalité de l’AMBA a été validésur six bâtiments réels excités par des vibrations ambiantes. D’après les résultats obtenus,AMBA a prouvé une grande efficacité dans l’estimation automatique des fréquences et destaux d’amortissement dans le cas de modes de fréquences rapprochées et avec un très faiblerapport signal-sur-bruit. AMBA a ainsi démontré une bonne performance pour suivre lesvariations modales au fil du tempsThis thesis proposes a novel approach to automatically monitor the variationsof the frequencies and the damping ratios of actual high-rise buildings subjected to realworldambient vibrations. The approach aims at dealing simultaneously with the followingchallenges: multi-component signals recorded over the aforementioned buildings and havingclosely-spaced frequency modes with low, exponential and damped amplitudes of theirimpulse responses and contaminated with high additive noises. The approach relies on theapplication of the Random Decrement Technique directly over the multi-component signalunder study which leads to the extraction of a Multi-mode Random Decrement Signatureequivalent to the system impulse response. To characterize such a signature, we propose asignal model based on the physical structure of the building from where the modal parameterscan be estimated. For the purpose of non-biased modal estimate, we propose to usean iterative method based on a Maximum-Likelihood Estimation optimized by a simulatedannealing technique. In order to initialize the parameters of the latter, a first step is designedwhich can be considered as an independent estimator of the modal parameters. Theoriginality of this step lies in its ability to automatically define the number of modes of theestimated signature through the use of the statistical properties of a Welch spectrum. Themodal parameters estimated by the spectral-based initialization step are finally refined bythe Maximum-Likelihood Estimation step. The latter reduces the bias in the estimation andyields more reliable and robust results. All these steps are defined in order to be able to automaticallymonitor the health of a building via a long-term real-time tracking of the modalvariations over time without the need to any user intervention . In addition, the proposedapproach has paid very special attention to the automatic estimation of the most problematicmodal parameter, i.e., the damping ratio. Such features making two of the original featuresas compared to existing techniques. The adaptability and functionality of AMBA is validatedover six actual buildings excited by real-world ambient vibrations. From the obtained results,AMBA proved high efficiency in automatically estimating the frequencies and moreover thedamping ratios in case of closely-spaced frequency modes and very low signal-to-noise ratiolevel. AMBA as well demonstrated a good performance for tracking the modal variationsover time
35
Remillieux, Marcel C. "Development of a Model for Predicting the Transmission of Sonic Booms into Buildings at Low Frequency". Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/27543.
Testo completoAbstract (sommario):
Recent progresses by the aircraft industry in the development of a quieter supersonic transport have opened the possibility of overland supersonic flights, which are currently banned by aviation authorities in most countries. For the ban to be lifted, the sonic booms the aircraft generate at supersonic speed must be acceptable from a human-perception point of view, in particular inside buildings. The problem of the transmission of sonic booms inside buildings can be divided in several aspects such as the external pressure loading, structure vibration, and interior acoustic response. Past investigations on this problem have tackled all these aspects but were limited to simple structures and often did not account for the coupled fluid-structure interaction. A more comprehensive work that includes all the effects of sonic booms to ultimately predict the noise exposure inside realistic building structures, e.g. residential houses, has never been reported. Thus far, these effects could only be investigated experimentally, e.g. flight tests.
In this research, a numerical model and a computer code are developed within the above context to predict the vibro-acoustic response of simplified building structures exposed to sonic booms, at low frequency. The model is applicable to structures with multiple rectangular cavities, isolated or interconnected with openings. The response of the fluid-structure system, including their fully coupled interaction, is computed in the time domain using a modal-decomposition approach for both the structural and acoustic systems. In the dynamic equations, the structural displacement is expressed in terms of summations over the â in vacuoâ normal modes of vibration. The interior pressure is expressed in terms of summations over the acoustic modes of the rooms with perfectly reflecting surfaces (hard walls). This approach is simple to implement and computationally efficient at low frequency, when the modal density is relatively low.
The numerical model is designed specifically for this application and includes several novel formulations. Firstly, a new shell finite-element is derived to model the structural components typically used in building construction that have orthotropic characteristics such as plaster-wood walls, floors, and siding panels. The constitutive matrix for these types of components is formulated using simple analytical expressions based on the orthotropic constants of an equivalent orthotropic plate. This approach is computationally efficient since there is no need to model all the individual subcomponents of the assembly (studs, sheathing, etc.) and their interconnections. Secondly, a dedicated finite-element module is developed that implements the new shell element for orthotropic components as well as a conventional shell element for isotropic components, e.g. window panels and doors. The finite element module computes the â in vacuoâ structural modes of vibration. The modes and external pressure distribution are then used to compute modal loads. This dedicated finite-element module has the main advantage of overcoming the need, and subsequent complications, for using a large commercial finite-element program. Lastly, a novel formulation is developed for the fully coupled fluid-structure model to handle room openings and compute the acoustic response of interconnected rooms. The formulation is based on the Helmholtz resonator approach and is applicable to the very low frequency-range, when the acoustic wavelength is much larger than the opening dimensions.
Experimental validation of the numerical model and computer code is presented for three test cases of increasing complexity. The first test structure consists of a single plaster-wood wall backed by a rigid rectangular enclosure. The structure is excited by sonic booms generated with a speaker. The second test structure is a single room made of plaster-wood walls with two double-panel windows and a door. The third test structure consists of the first room to which a second room with a large window assembly was added. Several door configurations of the structure are tested to validate the formulation for room openings. This latter case is the most realistic one as it involves the interaction of several structural components with several interior cavities. For the last two test cases, sonic booms with realistic durations and amplitudes were generated using an explosive technique. Numerical predictions are compared to the experimental data for the three test cases and show a good overall agreement.
Finally, results from a parametric study are presented for the case of the single wall backed by a rigid enclosure. The effects of sonic-boom shape, e.g. rise time and duration, and effects of the structure geometry on the fluid-structure response to sonic booms are investigated.Ph. D.
36
Massari, Elisa. "Dynamic characterisation of four nine-story large-panel R.C. buildings in Bishkek (Kyrgyzstan): A comparison between experimental ambient vibration analysis and numerical finite element modeling". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/9771/.
Testo completoAbstract (sommario):
With the outlook of improving seismic vulnerability assessment for the city of Bishkek (Kyrgyzstan), the global dynamic behaviour of four nine-storey r.c. large-panel buildings in elastic regime is studied. The four buildings were built during the Soviet era within a serial production system. Since they all belong to the same series, they have very similar geometries both in plan and in height.
Firstly, ambient vibration measurements are performed in the four buildings. The data analysis composed of discrete Fourier transform, modal analysis (frequency domain decomposition) and deconvolution interferometry, yields the modal characteristics and an estimate of the linear impulse response function for the structures of the four buildings. Then, finite element models are set up for all four buildings and the results of the numerical modal analysis are compared with the experimental ones. The numerical models are finally calibrated considering the first three global modes and their results match the experimental ones with an error of less then 20%.
37
Floresca, Diane Lee Bosuego 1979. "Research into building vibrations". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29550.
Testo completoAbstract (sommario):
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (leaf 63).
Underground and surface arteries for vehicle or railway traffic can create vibrations that travel to nearby buildings. These vibrations can cause structural damage or human discomfort. Displacement time histories collected from buildings abutting the central surface artery were used to drive mathematical models so that asphaltic and polymeric bearings could be studied as possible passive mitigators of such vibrations. Neither material attenuated vibrations to below threshold levels for human annoyance, but they could dampen levels to resist structural damage if enough material was used to bring the apparent natural frequency away from the range characteristic of traffic vibration. In addition, for resonant cases, the materials did not create enough damping force to counter the inertia of heavy structures, because the materials were too stiff and the displacements and velocities too small. For new construction, it is suggested that these vibrations should be prevented from entering the foundation area by surrounding the foundation with a concrete wall or absorbent foam blocks. For retrofits, polymeric or asphaltic pads could be used and would be relatively easy to install.
by Diane Lee Bosuego Floresca.
M.Eng.
38
Woodroof, Harry John. "Community response to railway-induced building vibration". Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/52278/.
Testo completoAbstract (sommario):
This study is an investigation of the subjective response to railway-induced building vibration. No previous study has obtained both subjective and objective measures from so many lineside residents: several hundred were interviewed and over fifty of the dwellings provided a site for a continuous 24 hour recording of building vibration. Annoyance caused by railway-induced building vibration, and the factors affecting annoyance, were investigated in a social survey. Of a sample of 720 adults living within 100 metres of railway lines in Scotland, 459 were interviewed; 160 of these noticed railway-induced building vibration. It is estimated that 1.4% of adults in Scotland notice railway-induced building vibration. Vibration was found to be amongst the least annoying aspects of a railway's presence in a neighbourhood. Vibration was recorded in 52 dwellings for 24 hours continuously in three axes. A method of isolating the portions of the 24 hour acceleration time-histories which represented perceptible railway-induced building vibration was developed. The severities of the isolated periods of the acceleration time-histories were assessed by 90 alternative measures chosen using the results of laboratory experiments. These had suggested that a vibration dose value (incorporating a fourth power relationship) was the most appropriate measure. The 90 measures were formed from combinations of different frequency weightings, time dependencies, averaging procedures and summing methods. Within-building differences in frequency and severity of vibration were found and differences occurred between similar, neighbouring, buildings. Frequency of vibration was influenced primarily by the characteristics of the building or the ground, rather than those of the passing trains. Horizontal vibration was generally below perception thresholds. The effect of different integration times used in root mean square averaging was demonstrated. No clear relationship was found between distance from the railway and severity of building vibration. Subjective response was found to be influenced primarily by the number of trains passing in 24 hours but not significantly affected by any of the characteristics of the vibration. It is concluded that this arose because railway-induced building vibration did not cause significant annoyance within the sample population. This conclusion does not deny the existence of individuals who were annoyed, or of individuals whose annoyance was influenced by the characteristics of the vibration. The conclusion that railway-induced building vibration did not cause significant annoyance within the sample population could not have been obtained from the questionnaire data alone. This demonstrates the importance of obtaining both objective and subjective measures when investigating subjective response to phenomena such as building vibration.
39
Laub, Errol (Errol Jonathan) 1976. "Design methodologies for controlling vibrations in buildings". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/33824.
Testo completoAbstract (sommario):
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.Includes bibliographical references (leaves 44-45).
Although vibration absorbers have been employed in mechanical equipment mounting for over 100 years, they have only recently been used for isolating large-scale structures such as bridges and buildings. Their applications range from acoustic to seismic isolation of structures. Virtually any vibration magnitude can be prevented from degrading the performance of a structure. This thesis is intended to provide a practical introduction to the design and suitability of vibration isolators for various environments. It contains a discussion of the past, present and future of vibration isolation associated with buildings. Analysis and design examples are provided to illustrate the design methodology.
by Errol Laub.
M.Eng.
40
Đerđ, Varju. "Teorijska i eksperimentalna analiza dinamičkog ponašanja jezgra visokih zgrada". Phd thesis, Univerzitet u Novom Sadu, Građevinski fakultet u Subotici, 2016. https://www.cris.uns.ac.rs/record.jsf?recordId=104682&source=NDLTD&language=en.
Testo completoAbstract (sommario):
U ovoj disertaciji, izvršena su teorijska i eksperimentalna istraživanja dinamičkog onašanja jezgra visokih zgrada. Model je zasnovan na Vlasovoj teoriji tankozidnih nosača, kao i na metodi prenosnih matrica. Jezgro se tretira kao tankozidni nosač otvorenog poprečnog preseka, koji je na dnu uklješten u temeljnu ploču, dok je na vrhu slobodan. Duž ose smicanja, jezgro je podeljeno na čvorove u nivoima spratova u kojima su redukovane mase. Poseban naglasak je stavljen na analizu uticaja poprečnih greda, međuspratnih ploča, kao i načinu oslanjanja međuspratnih ploča po spoljašnjoj konturi na dinamičke karakteristike jezgra. Razvijeni numerički postupak je primenjen na armiranobetonskom jezgru petnaestospratne zgrade, koja je analizirana ranijeu radovima mnogih autora. U tu svrhu korišćen je računarski program TWBEIG, napisan primenom Visual Fortran programskog jezika. Analize su urađene i MKE, a dobijeni rezultati su upoređeni. Vrednosti sopstvenih frekvencija pokazuju dobro slaganje.Ovaj rad daje detalje i o eksperimentalnoj studiji u kojoj se primenjuje pleksiglas model u cilju pružanja eksperimentalnih podataka zaproveru tačnosti i pouzdanosti numeričkih rezultata. Dobijeni rezultati su takođe upoređeni sa rezultatima dobijenim TWBEIG računarskim programom, kao i MKE.Predstavljeni numerički metod nudi solidnu osnovu za formiranje jednostavnog modela proračuna, a ipak obezbeđuje odgovarajući nivo preciznosti. Predloženi postupak može biti korišćen i u fazi prethodne analize zgrade, kao i u fazi konačnog projektovanja.In this dissertation, a theoretical and experimental study of the dynamic behaviourof the tall buildings core was carried out. The model is based on the Vlasov'stheory of thin-walled beams and the transfer matrixmethod. The core is treated asa thin wall-walled, open cross section cantilever beam. Along the shear axis thecore is divided into nodes, in the level of the floors, in which the masses arereduced. Special emphasis was given to the analysis of the influence, of lintelbeams, floor slabs, as well as the type of restraints along the outer edge of thefloor slabs, on the dynamic characteristics of the core.The developed numerical procedure was applied to the fifteen-storey reinforcedconcrete core tall building, analyzed previously inthe papers of many authors. Forthis purpose, the computer program TWBEIG was used, written using VisualFortran programming language. The analyses were also performed with FEM andsubsequently the results were compared. The values of natural frequencies showsignificant agreement. This paper presents details about the experimental study which applies the plexiglas model in order to provide experimental data to verify the accuracy and reliability of the numerical results. The results are also compared with the results obtained with the TWBEIG computer program, as well as with FEM. The values of frequencies show reasonable agreement.The proposed numerical method offers a solid base for the creation of a simplecalculation model, yet provides the appropriate level of precision. It can be eitherused for preliminary analysis or for the final design.
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BENEVELI, SUZANA MOREIRA AVILA. "HYBRID CONTROL FOR REDUCING BUILDING VIBRATIONS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3124@1.
Testo completoAbstract (sommario):
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORNo presente trabalho estuda-se a aplicação do controle estrutural na proteção de estruturas submetidas a carregamentos dinâmicos contra níveis de vibração indesejáveis que possam causar desconforto e, até mesmo, comprometer a segurança e integridade da edificação. Os três tipos de controle estrutural, passivo, ativo e híbrido, são analisados de forma a evidenciar as vantagens do uso do controle híbrido. O mecanismo de controle utilizado é o denominado amortecedor de massa sintonizado (AMS), devido à sua vasta aplicação na Engenharia Civil, tendo uma grande quantidade sido instalada em edifícios, pontes e chaminés industriais para controle de vibrações causadas pelo vento. Verifica-se a influência da não- linearidade da rigidez do AMS no comportamento do sistema principal. A utilização de amortecedores de massa sintonizados múltiplos é também estudada como uma forma de vencer certas limitações quanto à robustez deste tipo de sistema e melhorar sua performance. Analisa-se por fim o comportamento e eficiência do amortecedor de massa híbrido (AMH), em relação ao AMS passivo. Para cálculo da força de controle são utilizados os seguintes algoritmos: controle ótimo linear clássico, controle ótimo instantâneo e controle ótimo não-linear. Uma estratégia para definição das matrizes de ponderação, utilizadas no algoritmo de controle ótimo instantâneo, que minimizem a amplitude da resposta harmônica permanente é apresentada. Exemplos numéricos são apresentados ao longo de todo o trabalho. Verifica-se que a utilização do controle híbrido é mais eficiente que os controles passivo e ativo isolados, requerendo forças de magnitude inferiores, o que reduz bastante o custo deste tipo de sistema. O sistema de controle híbrido se mostrou eficiente na redução de vibrações causadas por carregamentos cujas freqüências eram diversas das consideradas no projeto do sistema de controle passivo. Verificou-se, ainda que o mesmo se comportou de forma satisfatória no caso de discrepância na freqüência natural da estrutura.
In this work the use of structural control is studied to protect dynamically loaded building structures against undesirable vibration levels, which can cause human discomfort and, even more, compromise the building safety and integrity. The three types of structural control, passive, ative and hybrid, are analysed to show the advantages of hybrid control in reducing undesirable vibration levels. The chosen control mechanism is the so called tuned mass damper (TMD), due to its large application in Civil Engineering, having a great number of these devices been installed in buildings, bridges and industrial chimneys to control structural vibrations induced by wind loads. It is also verified the influence of TMD non linear stiffness on the main system behaviour. The use of multiple tuned mass dampers is studied as a possible way of improving the TMD robustness and performance. The hybrid mass damper (HMD) behaviour and efficiency comparing to the passive mass damper is analysed in detail. To calculate the control force the following control algorithms are used: classical optimum linear control, instantaneous optimum control and non-linear optimum control. A strategy to define the weighting matrices used in the instantaneous optimum control algorithm that minimizes the harmonic response amplitude is presented. Several numerical examples are presented aalong the work. The results show that the hybrid control is more efficient that the passive or active control used separately, requiring smaller forces reducing in this way the cost of the control system. The hybrid control system showed to be more efficient in reducing vibrations caused by loadings which had different frequencies from that considered on the passive control design. Moreover it was shown that hybrid control has a satisfactory perfomance when discrepancies in natural frequency occur.
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Widjaja, T. R. "Vibration transmission between two nominally identical building floors". Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496482.
Testo completo
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May, James E. "Non-Linear Control of Long, Flexible Structures Employing Inter-Modal Energy Transfer [Modal Damping]". University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1247711518.
Testo completo
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Hofstetter, Marcel, e Nima Pashai. "Soil-structure interaction for traffic induced vibrations in buildings". Thesis, KTH, Bro- och stålbyggnad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-233001.
Testo completoAbstract (sommario):
Major cities in Sweden experience a population growth, demanding innovative solutions regarding land exploitation for residential housing. One solution is to build closer to existing railway tracks, however difficulties arise regarding determining traffic induced vibrations from trains. This sometimes results in vibrations being too large in buildings regarding comfort, resulting in expensive measures taken as to reduce the vibrations. The scope of this thesis is to investigate the soil-structure interaction caused by traffic induced vibrations in buildings using ABAQUS FE software, where the aim is to partly investigate how a structure effects surrounding soil, partly to investigate which parameters of a structure has largest favorable impact on foundation vibrations. Major results include that ground vibrations at 2-4 meters parallel to a structure relative to the vibration source remain constant, independent on whether a house is present or not. Further results show that increasing the thickness of the foundation slab has a mitigating effect on the induced vibrations. The main conclusions of this thesis include that quadratic elements are superior to linear elements for dynamic analyses for soil, and that accelerometers should be placed at least 2-4 m next to an existing structure to obtain accurate measurements comparable to if no structure was present.Större städer i Sverige upplever en befolkningstillväxt, vilket resulterar i att kreativa lösningar måste introduceras gällande markexploatering för bostadshus. En sådan lösning är att bygga närmre befintlig järnväg, dock resulterar detta i svårigheter gällande att kvantifiera magnituden av trafikinducerade vibrationer i byggnadsfundament orsakade av tågtrafik. En konsekvens av detta är att vibrationsnivåerna i husen ibland blir för stora sett till komfortvibrationer, vilket resulterar i att dyra åtgärder måste tas för att minska vibrationerna. Denna avhandling syftar till att genom att använda ABAQUS FE-mjukvara utforska jord-strukturinverkan i hus orsakade av trafikvibrationer. Målet är delvis att undersöka hur byggnation påverkar omgivande markvibrationer, delvis att undersöka vilka parametrar som har störst gynnsam effekt gällande dämpning av trafikinducerade vibrationer. De viktigaste resultaten indikerar att markvibrationer 2-4 meter bredvid ett hus relativt vibrationskällan förblir oförändrade oberoende av om byggnation existerar eller ej, samt att en ökning av tjockleken av grundplattan resulterar i minskade fundamentvibrationer. Slutsatserna som presenteras är flera, däribland att kvadratiska element är mer beräkningseffektiva än linjära element för dynamiska analyser för jord, samt att accelerometrar bör placeras minst 2-4 m bredvid ett befintligt hus för att erhålla mätdata jämförbara med om ett hus inte skulle finnas på platsen.
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Bolmsvik, Åsa. "Structural-acoustic vibrations in wooden assemblies: : Experimental modal analysis and finite element modelling". Doctoral thesis, Linnéuniversitetet, Institutionen för bygg- och energiteknik (BE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-24562.
Testo completoAbstract (sommario):
This doctoral thesis concerns flanking transmission in light weight, wooden multi-storey buildings within the low frequency, primarily 20-120 Hz. The overall aim is to investigate how the finite element method can contribute in the design phase to evaluate different junctions regarding flanking transmission. Two field measurements of accelerations in light weight wooden buildings have been evaluated. In these, two sources; a stepping machine, and an electrodynamic shaker, were used. The shaker was shown to give more detailed information. However, since a light weight structure in field exhibit energy losses to surrounding building parts, reliable damping estimates were difficult to obtain. In addition, two laboratory measurements were made. These were evaluated using experimental modal analysis, giving the eigenmodes and the damping of the structures. The damping for these particular structures varies significantly with frequency, especially when an elastomer is used in the floor-wall junction. The overall damping is also higher when elastomers are used in the floor-wall junction in comparison to a screwed junction. By analysing the eigenmodes, using the modal assurance criterion, of the same structure with two types of junctions it was concluded that the modes become significantly different. Thereby the overall behavior differs. Several finite element models representing both the field and laboratory test setups have been made. The junctions between the building blocks in the models have been modeled using tie or springs and dashpots. Visual observation and the modal assurance criterion show that there is more rotational stiffness in the test structures than in the models. The findings in this doctoral thesis add understanding to how modern joints in wooden constructions can be represented by FE modelling. They will contribute in developing FE models that can be used to see the acoustic effects prior to building an entire house. However, further research is still needed.Denna doktorsavhandling behandlar flanktransmission i flervåningshus med trästomme, inom det lågfrekventa området, främst 20-120 Hz. Det övergripande målet är att undersöka hur finita elementmetoden kan bidra i konstruktionsfasen för att utvärdera olika knutpunkters inverkan på flanktransmissionen. Två fältmätningar av accelerationer i trähus har utvärderats. I dessa har två olika lastkällor använts, i den första en stegljudsapparat och i den andra en elektrodynamisk vibrator (shaker). Det visades att shakern kan ge mer detaljerad information, men eftersom vibrationerna även sprider sig till omgivande byggnadsdelar vid fältmätningarna var det svårt att estimera tillförlitliga dämpningsdata även då shaker användes. Fältmätningarna följdes av två mätningar i laborationsmiljö. Dessa två experiment utvärderades med experimentell modalanalys, vilket ger egenmoder och dämpning hos strukturerna. Dämpningen för dessa trähuskonstruktioner varierar kraftigt med frekvens. Extra stora variationer registreras då en elastomer användes i knutpunkten mellan golv och vägg. Den totala dämpningen är generellt högre när elastomerer används i knutpunkten mellan golv och vägg i jämförelse med då knutpunkten är skruvad. Genom att analysera egenmoder och deras korrelationer (MAC), för samma trästruktur men med olika typer av knutpunkter, drogs slutsatsen att knutpunkten drastiskt förändrar strukturens dynamiska beteende. Flera finita elementmodeller av både fält- och laboratorieuppställningar har gjorts. I dessa har knutpunkterna mellan byggnadsdelar modellerats helt styvt eller med hjälp av fjädrar och dämpare. Visuella observationer av egenmoder och korrelationen dem emellan visar att det finns mer rotationsstyvhet i försöken än i finita elementmodellerna. Resultaten i denna doktorsavhandling har gett förståelse för hur knutpunkter i träkonstruktioner beter sig och kan simuleras med finit elementmodellering. Vidare kan resultaten bidra till utvecklingen av FE-modeller som kan användas för att kunna se de akustiska effekterna redan under konstruktionsstadiet. Dock behövs ytterligare forskning inom området.
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Yeung, Ngai. "Viscous-damping walls for controlling wind-induced vibrations in buildings". Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B2324205X.
Testo completo
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Karlberg, Victor. "Dynamic analysis of high-rise timber buildings : A factorial experiment". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65559.
Testo completoAbstract (sommario):
Today high-rise timber buildings are more popular than ever and designers all over the world have discovered the beneficial material properties of timber. In the middle of the 1990’s cross-laminated timber (CLT), was developed in Austria. CLT consists of laminated timber panels that are glued together to form a strong and flexible timber element. In recent years CLT has been on the rise and today it is regarded as a good alternative to concrete and steel in the design of particularly tall buildings. Compared to concrete and steel, timber has lower mass and stiffness. A high-rise building made out of timber is therefore more sensitive to vibration. The vibration of the building can cause the occupants discomfort and it is thus important to thoroughly analyze the building’s dynamic response to external excitation. The standard ISO 10137 provides guidelines for the assesment of habitability of buildings with respect to wind-induced vibration. The comfort criteria herein is based on the first natural frequency and the acceleration of the building, along with human perception of vibration. The aim of this thesis is to identify the important structural properties affecting a dynamic analysis of a high-rise timber building. An important consequence of this study is hopefully a better understanding of the interactions between the structural properties in question. To investigate these properties and any potential interactions a so-called factorial experiment is performed. A factorial experiment is an experiment where all factors are varied together, instead of one at a time, which makes it possible to study the effects of the factors as well as any interactions between these. The factors are varied between two levels, that is, a low level and a high level. The design of a factorial experiment includes all combinations of the levels of the factors. The experiment is performed using the software FEM-Design, which is a modeling software for finite element analysis. A fictitious building is modelled using CLT as the structural system. The modeling and the subsequent dynamic analysis is repeated according to the design of the factorial experiment. The experiment is further analyzed using statistical methods and validated according to ISO 10137 in order to study performance and patterns between the different models. The statistical analysis of the experiment shows that the height of the building, the thickness of the walls and the addition of mass are important in a dynamic analysis. It also shows that interaction is present between the height of the building and the thickness of the walls as well as between the height of the building and the addition of mass. Most of the models of the building does not satisfy the comfort criteria according to ISO 10137. However, it still shows patterns that provides useful information about the dynamic properties of the building. Lastly, based on the natural frequency of the building this study recognizes the stiffness as more relevant than the mass for a building with CLT as the structural system and with up to 16 floors in height.Idag är höga trähus mer populära än någonsin och konstruktörer runtom i världen har upptäckt de fördelaktiga materialegenskaperna hos trä. I mitten på 1990-talet utvecklades korslimmat trä (KL-trä) i Österrike. KL-trä består av hyvlade brädor som limmas ihop för att bilda en lätt och stark träskiva. På senare år har KL-trä varit på uppgång och idag anses materialet vara ett bra alternativ till betong och stål i framför allt höga byggnader. Jämfört med betong och stål har trä både lägre massa och styvhet. En hög träbyggnad är därför mer känslig för vibrationer. En vibrerande byggnad kan leda till obehag för de boende och det är därför viktigt att analysera byggnadens dynamiska respons då den utsätts för yttre belastning. Standarden ISO 10137 ger riktlinjer för att kunna utvärdera komfortkravet för byggnader med avseende på människors känslighet för vibrationer orsakade av vind. Komfortkravet i fråga jämför byggnadens första naturliga egenfrekvens med dess acceleration. Syftet med detta examensarbete är att identifiera de viktiga egenskaperna i en dynamisk analys av en hög träbyggnad. Förhoppningsvis leder det här examensarbetet till en ökad förståelse av samspelseffekterna mellan dessa egenskaper. För att undersöka dessa egenskaper och eventuella samspelseffekter genomförs ett så kallat faktorförsök. Ett faktorförsök är ett försök där alla faktorer varieras tillsammans, istället för en och en, vilket gör det möjligt att studera effekterna av faktorerna samt eventuella samspelseffekter. Faktorerna varieras mellan två nivåer: en låg nivå och en hög nivå. Ett faktorförsök använder sig av samtliga kombinationer av faktorernas nivåer. Försöket utförs med hjälp av programmet FEM-Design, vilket är ett modelleringsverktyg för FE-analys. En fiktiv byggnad modelleras med CLT som stomsystem och en dynamisk analys görs. Försöket analyseras ytterligare med hjälp av statistiska metoder och valideras enligt ISO 10137. Dessa steg upprepas enligt faktorförsöket. Den statistiska analysen av försöket visar att höjden på byggnaden, tjockleken på väggarna samt en ökad massa är viktiga i en dynamisk analys. Den visar också på en samspelseffekt mellan höjden på byggnaden och tjockleken på väggarna, samt mellan höjden på byggnaden och en ökad massa. Merparten av modellerna av byggnaden uppfyller inte komfortkravet enligt ISO 10137. Däremot går det att urskönja mönster som bidrar med viktig information om byggnadens dynamiska egenskaper. Avslutningsvis, baserat på byggnadens naturliga egenfrekvens framhåller den här studien byggnadens styvhet framför dess massa då byggnaden i fråga stabiliseras med KL-trä och har upp till 16 våningar.
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Hudson, Emma J. "Incorporating active control of human-induced vibrations in floors into buildings". Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4313/.
Testo completoAbstract (sommario):
This thesis investigates the implications of incorporating active vibration control (AVC) into floor structures from the initial design stage, with the goal of enabling the construction of more slender long-span floors. The original contributions to knowledge in this work are the investigations into: the development of a novel walking force that simulates the in-service loading of an office environment; the comparison between the effectiveness of AVC and tuned mass dampers (TMDs) when used on floor structures; the investigation into the effect of AVC over the entire floor area rather than considering single locations only, leading to conclusions about typical numbers of actuators that would be required; the investigation into the trade-off between power demand and the performance of an AVC system; and the initial life cycle analysis (LCA) of a floor that incorporates AVC at the design stage. The force model utilises simultaneous pedestrians walking throughout the structure and was calibrated and verified using experimentally acquired data. AVC was found to be a significant improvement upon TMDs in that the response of the structure was reduced to a greater extent using a much smaller inertial masses. The effectiveness of AVC was generally limited to within a single bay. However, large reductions in response were observed within each controlled bay. Therefore, it is suggested that a rule of thumb of one actuator per significant panel is required to control a given floor area, and that the size of these bays should be maximised to increase the effectiveness of AVC. High feedback gains resulted in only slight improvements in structural response, therefore improvements in the non-overhead power demand for AVC can be achieved through a simple decrease in the feedback gain. This has the additional benefit that smaller actuators could be utilised. The initial LCA highlighted the high financial cost of AVC but also demonstrated that potentially significant material savings could be realised through incorporation of AVC at the design stage.
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Oskarsson, Adam. "Transmission of Vibrations in Precast Concrete Slabs". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79119.
Testo completoAbstract (sommario):
Dynamic loads have historically not been a troubled area for concrete floors, foremostbecause of the high self-weight compared to the dynamic load. With new technical andcalculation achievements during the last decades concrete floors have become longerand more slender. This have led to more open plan structures with longer spans thatmake concrete floors more sensitive to vibrations.This thesis studies the dynamic effects of hollow concrete core elements induced by co-ordinated jumping and the vibration levels that spread to the floor above. The thesisinvestigates different standards and guides on how to perform a dynamic analysis andevaluate it. In the thesis an experiment was conducted on WSP Sweden headquar-ters in Stockholm. The fifth and sixth floor of the building was investigated in thisthesis. The floors are made of hollow concrete core elements of the type HD/F 120/27.First a so-called heel drop test was done on the fifth floor to evaluate the naturalfrequency of the floor. The floors were monitored while 12 people performed coordi-nated jumping. Three accelerometers were placed on the fifth floor where the load wasapplied and one on the floor above.The results from the experiment and simulation were evaluated with three methodsISO 10137, National Building Code of Canada and Design Guide - Floor VibrationsDue to Human Activity. The data from the experiment shows that the upper floor isunsuitable for office use for 2 standards. The lower floor is viewed as acceptable formore carefree setting such as shopping malls.A finite element analysis of the building was done in the program Brigade. The modelconsists of one wing of the building and the fifth and sixth floor. The remaining floorsare modelled as equivalent mass. The columns were modeled down to the fourth floorand the beams for the fifth and six floors were included. A stairwell between the fifthand sixth floor was also modelledEvaluation of the finite element results was done in the same fashion as the experi-ment. Here the upper floor was performing satisfactory for office use and the lowerfloor was similarly as the experiment above accepted for settings where more acceler-ation is considered acceptable such as for restaurants and shopping malls.The maximum transient vibration value (MTVV) results from the experiment andsimulation was compared and the lower floor was conforming pretty well with a dif-ference smaller than 1 % to around 30 % depending on the accelerometer. However,the results for the upper floor differs significantly, as the difference is about 770 %between the experiment and simulation. The finite element model is not able to ac-curately represent the real building for the acceleration of the upper floor. This couldbe explained by the the absence of partition walls for meeting rooms, copying room,toilets and the facade. Since this could limit the acceleration that is transmitted fromthe lower floor to the upper floor.
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Al-Anbaki, Atheer Faisal Hameed. "Footfall excitation of higher modes of vibration in low-frequency building floors". Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34081.
Testo completoAbstract (sommario):
This thesis investigates the footfall excitation of higher modes of vibration in low-frequency floor structures. This is motivated by the increased number of floors reportedly failing to meet the required occupants comfort level although being designed in accordance with the current state-of-the-art design guidelines. In particular modern, lightweight, and slender floor structures. The contribution to knowledge of this thesis can be summarised as: quantifying the signal energy of measured walking forces within and above the natural frequency cut-off proposed by the current state-of-the-art design guidelines; quantifying the contribution of higher modes of vibration to the overall response of low-frequency floors to human walking; propose measures to judge the response nature of low-frequency floors, these are the relevant change of the point stiffness and the shape of frequency response functions; proposing a frequency-domain approach that enables designers to include higher modes of vibration in the design against human-induced vibration. It was found that the signal energy of walking forces is distributed well beyond the natural frequency cut-off proposed by the current state-of-the-art design guidelines. Also, the contribution of localised, higher, modes of vibration to the overall response of ultra-lightweight floors was significant. Moreover, it was found that higher modes affect the response of floors of various construction types in one way or another. Hence, it was recommended to consider their contribution in the design of floors against human-induced vibration. Also, it was found that the higher the relative change of the point stiffness the more higher modes contribute to the overall response of floors. Finally, the frequency-domain analysis was found less expensive than time-domain analysis and could result in similarly useful information.