The purpose of this research is to establish the effectiveness of tuned-mass-dampers (TMD) using semi-active magneto-rheological (MR) dampers to mitigate annoying floor vibrations. Annoying floor vibration is becoming more common in today's building structures since building materials have become stronger and lighter; the advent of computers has resulted in "paperless" offices; and the use of floors for rhythmic activities, such as aerobics and concerts, is more common. Analytical and experimental studies were conducted to provide an understanding of the effects of incorporating the semi-active-TMD as a remedy to annoying floor vibration. A pendulum tuned mass damper (PTMD) in which the tuning parameters could independently be varied was used. Closed form solutions for the response of the floor using passive dampers were developed. In addition, a numerical integration technique was used to solve the equations of motion where semi-active dampers are utilized. The optimum design parameters of PTMDs using passive and semi-active dampers were found using an optimization routine. Performances of the PTMD in reducing the floor vibration level at the optimum and when subjected to off-tuning of design parameters using passive and semi-active dampers were compared. To validate the results obtained in the analytical investigation, an experimental study was conducted using an 8 ft x 30 ft laboratory floor and a commercial PTMD. Comparative studies of the effectiveness of the PTMD in reducing floor vibrations using semi-active and passive dampers were conducted. / Master of Science

Floor vibrations due to occupancy activities on a floor are sometimes annoying to the occupants. Correcting floor vibrations is difficult and can be expensive. The use of tuned mass dampers to control annoying floor vibrations is sometimes a viable solution. Tuned mass dampers (TMDs) have been used primarily to control only one or two modes of vibration of a floor. Experimental research was performed using prototype TMDs to control one, two, and three modes of vibration of various floors. Results from this research are presented in this thesis. Analytical research, performed to obtain information about floor vibration characteristics, is presented and used for the initial design of TMDs and placement of TMDs on a floor. Also, computer models of the floors with TMDs to control one, two, and three modes of vibration were analyzed to obtain further information about changes in floor response and vibration characteristics. This research was performed to provide further insight on the effectiveness of TMDs to control one, two, and three modes of floor vibration and the effects of TMDs on floor vibration characteristics. / Master of Science

The use of cold-formed steel as a framework for floor systems in multi-story buildings and single occupancy residences is becoming an increasingly popular alternative to traditional materials and techniques. Builders and designers have recognized that the high strength-to-weight ratio provided by the cross-section of cold-formed steel members permits lighter structures and longer spans. The longer spans and lighter structures associated with cold-formed steel floor systems can result in vibration serviceability issues if proper design considerations are not made. Providing sufficient damping within the structure is the most effective way to ensure that occupants are comfortable under typical residential and office service loads. The modern, open-concept interior has open floor plans with few partitions and long spans, which result in inherently low structural damping. Cold-formed steel floor systems also have less mass than traditional floor systems, which will increase the amplitude of acceleration response. The vibration problems that may be present in cold-formed steel floor systems, like any other floor system, can be addressed if proper consideration is given by designers. Traditional design approaches for vibration serviceability have proven inadequate, and there are no current methods available to designers for calculating the response of cold-formed steel floor systems. In order to design a floor system to properly address occupant comfort, consideration must be given for the type of dynamic loading, resonance, dynamic response, and stiffness of the floor system. The objective of this thesis is to improve the understanding of the dynamic characteristics of cold-formed steel floor systems, and recommend an adequate model for predicting the dynamic response and modal properties of floor systems, in order to aid the design process. This thesis presents the results of an extensive laboratory and field study on the vibration of cold-formed steel floor systems. Floor systems built with cold-formed steel TreadyReady® joists and subfloor assemblies containing OSB, FORTACRETE®, sound reduction board, cold-formed steel deck, and LEVELROCK® topping were examined. Previous research has presented the observed influence of construction details on the modal properties of the laboratory floor systems tested. This thesis discusses the influence of different details on the transverse stiffness of the floor systems. It was found that effectively restrained strongbacks, and cold-formed steel deck subfloor assemblies provided significant increases in transverse stiffness. Based on the analysis of the field testing data, recommended design damping ratios are provided for floor systems constructed with the materials investigated in this study. Floor response that can be compared to serviceability criteria is presented. The peak RMS acceleration from walking excitation was found to be within the acceptable range for the ISO criterion based on residential occupancy, and the static deflection from a 1 kN point load was found to be within the acceptable range of Onysko’s criterion. An adequate design criterion for vibration requires a limiting value, and a means of estimating floor response for comparison. The AISC, ATC, and Smith, Chui, and Hu Orthotropic Plate design methods were evaluated by comparing predicted frequency against measured frequency for the test floors. The ATC and Smith, Chui, and Hu Orthotropic Plate methods were evaluated by comparing predicted deflection against measured deflection for the test floors. The ATC method is recommended as the best method for calculating floor response based on current publications. A design procedure is recommended for cold-formed steel floor systems, using the ATC design guide. The ATC acceleration criterion for walking excitation must be met for floors with fundamental frequencies of less than 15 Hz, and the ATC static deflection criterion must be met for all floors. Proposed modifications to the ATC method to improve the design of cold-formed steel floors include: adopting the recommended design damping ratios from this thesis; adopting the frequency-weighted ISO limiting acceleration and, obtaining several coefficients and empirical expressions that are relevant to cold-formed steel floors from further testing. Recommendations for improving the floor testing procedures at the University of Waterloo are given.

The use of cold-formed steel as a framework for floor systems in multi-story buildings and single occupancy residences is becoming an increasingly popular alternative to traditional materials and techniques. Builders and designers have recognized that the high strength-to-weight ratio provided by the cross-section of cold-formed steel members permits lighter structures and longer spans. The longer spans and lighter structures associated with cold-formed steel floor systems can result in vibration serviceability issues if proper design considerations are not made. Providing sufficient damping within the structure is the most effective way to ensure that occupants are comfortable under typical residential and office service loads. The modern, open-concept interior has open floor plans with few partitions and long spans, which result in inherently low structural damping. Cold-formed steel floor systems also have less mass than traditional floor systems, which will increase the amplitude of acceleration response. The vibration problems that may be present in cold-formed steel floor systems, like any other floor system, can be addressed if proper consideration is given by designers. Traditional design approaches for vibration serviceability have proven inadequate, and there are no current methods available to designers for calculating the response of cold-formed steel floor systems. In order to design a floor system to properly address occupant comfort, consideration must be given for the type of dynamic loading, resonance, dynamic response, and stiffness of the floor system. The objective of this thesis is to improve the understanding of the dynamic characteristics of cold-formed steel floor systems, and recommend an adequate model for predicting the dynamic response and modal properties of floor systems, in order to aid the design process. This thesis presents the results of an extensive laboratory and field study on the vibration of cold-formed steel floor systems. Floor systems built with cold-formed steel TreadyReady® joists and subfloor assemblies containing OSB, FORTACRETE®, sound reduction board, cold-formed steel deck, and LEVELROCK® topping were examined. Previous research has presented the observed influence of construction details on the modal properties of the laboratory floor systems tested. This thesis discusses the influence of different details on the transverse stiffness of the floor systems. It was found that effectively restrained strongbacks, and cold-formed steel deck subfloor assemblies provided significant increases in transverse stiffness. Based on the analysis of the field testing data, recommended design damping ratios are provided for floor systems constructed with the materials investigated in this study. Floor response that can be compared to serviceability criteria is presented. The peak RMS acceleration from walking excitation was found to be within the acceptable range for the ISO criterion based on residential occupancy, and the static deflection from a 1 kN point load was found to be within the acceptable range of Onysko’s criterion. An adequate design criterion for vibration requires a limiting value, and a means of estimating floor response for comparison. The AISC, ATC, and Smith, Chui, and Hu Orthotropic Plate design methods were evaluated by comparing predicted frequency against measured frequency for the test floors. The ATC and Smith, Chui, and Hu Orthotropic Plate methods were evaluated by comparing predicted deflection against measured deflection for the test floors. The ATC method is recommended as the best method for calculating floor response based on current publications. A design procedure is recommended for cold-formed steel floor systems, using the ATC design guide. The ATC acceleration criterion for walking excitation must be met for floors with fundamental frequencies of less than 15 Hz, and the ATC static deflection criterion must be met for all floors. Proposed modifications to the ATC method to improve the design of cold-formed steel floors include: adopting the recommended design damping ratios from this thesis; adopting the frequency-weighted ISO limiting acceleration and, obtaining several coefficients and empirical expressions that are relevant to cold-formed steel floors from further testing. Recommendations for improving the floor testing procedures at the University of Waterloo are given.

In the light of today’s effort to achieve sustainable future of the planet, timber as building material makes a comeback on the construction market. Since the requirements on the buildings and the internal comfort increase, there is a need for finding new solutions and products; one of them is cross-laminated timber (CLT), which has the potential to be used for high-rise buildings due to its mechanical properties. The aim of this work was to study the vibration performance of CLT floors as it is often the governing factor in design of CLT structures unlike for other common building materials. The orthotropic mechanical properties of CLT were determined by the shear analogy method and verified with a finite element (FE) model of a simply supported beam compared to hand calculations of shear forces, bending moments and deflections. The properties based on Timoshenko’s approach were evaluated as less precise regarding the deflection. The non-composite structural behaviour of a steel-CLT hybrid floor structure was predicted for FE dynamic analysis based on a comparison between modelling exercise and hand calculations. Two different methods, the Concrete Society (SC) and Steel Construction Institution (SCI) methods, both seemed to be applicable for determination of the response factor first since the mechanical properties are not used as input in the calculations. These two methods differ in certain aspects, and based on FE analysis of simply supported slab even the resulting response factor for the CLT differs significantly. Moreover, the hand calculation results were similar to those of the FE analysis for the CS method, but in less agreement for the SCI method. Nevertheless, it is not recommended to reject the latter method based on this study and further studies should be performed on real structures with response factor known from on-site measurements. A part of the first floor of Canary Wharf College was modelled and analysed, and previous measurements of the frequency and response factors enabled a validation of some assumptions. The SCI approach showed to be inadequate for this type of structure and therefore only the CS method was applied further. Analysis of the floor structures supported by walls demonstrated similar results from both the measurements and the dynamic analysis. However, if the floor slab was supported by beams, the response factor was significantly overestimated although on the conservative side. This difference suggests that the modelling of such conditions are not satisfactory. The CS method appears to assess correctly the magnitude of the response factor for CLT floors supported by walls but overestimates it in case of beam supports. The first finding shall be confirmed through analysis of other structures and a more extensive research should focus on the latter one to determine more exact behaviour of the model under different conditions.

Floors have traditionally been designed only for strength and deflection serviceability. As technological advances have been made in medical, scientific and micro-electronics manufacturing, many types of equipment have become sensitive to vibration of the supporting floor. Thus, vibration serviceability has become a routinely evaluated limit state for floors supporting sensitive equipment. Equipment vibration tolerance limits are sometimes expressed as waveform peak acceleration, and are more often expressed as narrowband spectral acceleration, or one-third octave spectral velocity. Current floor vibration prediction methods, such as those found in the American Institute of Steel Construction Design Guide 11, Floor Vibrations Due to Human Activity, the British Steel Construction Institute P354, Design of Floors for Vibration: a New Approach and the British Concrete Centre CCIP-016 A Design Guide for Footfall Induced Vibration of Structures, have limitations. It has been observed that non-structural components such as light-weight partitions could significantly change floor dynamic properties. Current prediction methods do not provide a fundamental frequency manual prediction method nor finite element modeling guidance for floors with non-structural components. Current prediction methods only predict waveform peak acceleration and do not provide predictions for frequency domain response including narrowband spectral acceleration or one-third octave spectral velocity. Also, current methods are not calibrated to provide a specific level of conservatism. This research project provides (1) a fundamental frequency manual prediction method for floors with lightweight partitions; (2) an improved finite element modeling procedure for floors with light-weight partitions; (3) a procedure to predict the vibration response in narrow-band spectrum and one-third octave band spectrum which can be directly compared with vibration tolerance limits; and (4) a simplified experimental procedure to estimate the floor natural frequencies. An experimental program including four steel-framed building floors and a concrete was completed. Modal tests were performed on two of the steel-framed buildings and the concrete building using an electrodynamic shaker. Experimental modal analysis techniques were used to estimate the modal properties: natural frequencies, mode shapes, and damping ratios. Responses to walking excitation were measured several times in each tested bay for individuals walking at different walking speeds. During each test, the walker crossed the middle of the bay using a metronome to help maintain the intended cadence. The proposed method was used to predict the modal properties and responses to walking. The measurements are used to assess the precision of the proposed methods and to calibrate the prediction methods to provide a specific probability that the actual response will exceed the predicted response. Comparison of measurements and predictions shows the proposed methods are sufficiently accurate for design usage.

Steel-deck composite floor systems are being increasingly used in high-rise building construction, especially in Australia, as they are economical and easy to construct. These composite floor systems use high strength materials to achieve longer spans and are thus slender. As a result, they are vulnerable to vibration induced under service loads. These floors are normally designed using static methods which will not reveal the true behaviour and miss the dynamic amplifications resulting in inappropriate designs, which ultimately cause vibration and discomfort to occupants. At present there is no adequate design guidance to address the vibration in these composite floors, due to a lack of research information, resulting in wasteful post event retrofits. To address this gap in knowledge, a comprehensive research project is presented in this thesis, which investigated the dynamic performance of composite floors under various human induced loads. A popular type of composite floor system was selected for this investigation and subjected to load models representing different human activities. These load models have variable parameters such as load intensity, activity type (contact ratio), activity frequency and damping and are applied as pattern loads to capture the maximum responses in terms of deflections and accelerations. Computer models calibrated against experimental results are used in the analysis to generate the required information. The dynamic responses of deflections and accelerations are compared with the serviceability deflection limits and human comfort levels (of accelerations) to assess these floor types. This thesis also treats the use of visco-elastic (VE) dampers to mitigate excessive vibrations in steel-deck composite floors. VE damper properties have been presented and their performances in reducing the excessive vibrations have been assessed this thesis. The results identified possible occupancies under different loading conditions that can be used in planning, design and evaluation. The findings can also be used to plan retrofitting measures in problematic floor systems.

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / Atualmente, as novas tendências arquitetônicas e as exigências de mercado, vêm conduzindo a engenharia estrutural na busca por soluções cada vez mais arrojadas, as quais exigem grande experiência e conhecimento dos projetistas estruturais aliados a utilização de novos materiais e tecnologias. Esta filosofia de concepção estrutural está inserida em uma das mais importantes tendências de projeto dos últimos anos, ou seja: a busca por sistemas estruturais de rápida execução, dotados de peças de menor peso próprio e que possam vencer grandes vãos com um mínimo de elementos verticais, permitindo assim uma maior flexibilidade na adequação de ambientes. Por outro lado, esta filosofia de projeto tem conduzido a elementos estruturais cada vez mais esbeltos e com freqüências naturais cada vez mais baixas e, por conseguinte, mais próximas das faixas de freqüência das excitações dinâmicas associadas às atividades humanas, tais como: andar, correr, pular, etc. Devido as razões expostas no parágrafo anterior, os sistemas estruturais de engenharia tornaram-se bastante vulneráveis aos efeitos de vibrações induzidas por pequenos impactos como é o caso do caminhar de pessoas sobre pisos, resultando em desconforto para as pessoas. Deve-se destacar, ainda, que tais considerações de projeto têm atendido aos estados limites últimos. Todavia, os estados limites de utilização desses sistemas estruturais precisam ser analisados, sem sombra de dúvida, de maneira mais criteriosa. Deste modo, no sentido de contribuir para fornecer subsídios aos engenheiros estruturais, no que tange a análise dinâmica de estruturas submetidas a excitações induzidas pelos seres humanos, são desenvolvidos diversos modelos de carregamento representativos do caminhar das pessoas. A variação espacial e temporal da carga dinâmica é considerada ao longo da análise e, bem como, o efeito transiente do impacto do calcanhar humano nos pisos é levado em conta. Assim sendo, são considerados nesta dissertação diversos modelos estruturais associados a pisos mistos (aço-concreto). Técnicas usuais de discretização, com base no emprego do Método dos Elementos Finitos (MEF), via utilização do programa computacional Ansys, são consideradas neste estudo. Uma análise extensa acerca da resposta dinâmica dos pisos é feita, mediante o emprego dos modelos de carregamento desenvolvidos, principalmente, em termos dos valores das acelerações. Na seqüência, os resultados encontrados são comparados com aqueles fornecidos pela literatura técnica disponível sobre o assunto sob o ponto de vista associado ao conforto humano. Investiga-se, também, a influencia da variação de parâmetros estruturais sobre a resposta dinâmica dos modelos, tais como: comprimento vão, taxa de amortecimento, espessura das lajes e, ainda, rigidez das ligações viga coluna. Os resultados obtidos ao longo do estudo indicam, claramente, que os projetistas estruturais devem ser alertados para distorções importantes que ocorrem quando as normas de projeto são utilizadas sem o devido cuidado. Um outro importante diz respeito ao fato de que em diversos pisos analisados observa-se que os critérios de conforto humano não são satisfeitos, demonstrando a importância da consideração dos efeitos dinâmicos provenientes dos seres humanos na análise desse tipo de problema. / Nowadays, the new architectural tendency and the market requirements, are leading structural engineering in the search for bolder solutions, which demands great experience and knowledge of the structural designers associated to the use of new materials and technologies. This philosophy of structural conception is inserted in one of the most important trends of project of the last years that means: the search for structural systems of fast execution, endowed with parts of lower weight and that can be successfully large with a minimum of vertical elements, thus allowing a higher flexibility in the ambients adequacy. On the other hand, this project philosophy has lead to structural elements more and more slender and with natural frequencies much and much lower and, therefore, closer to the frequency of the dynamic excitation associated to the human beings activities, such as: walking, running, jumping, etc. Due to the reasons described in the previous paragraph, the structural engineering systems became sufficiently vulnerable to the effects of vibrations induced by small impacts as it is the case of walking of people on floors, resulting in discomfort to the people. It must be highlighted, also, that such project considerations have fulfilled the required limit states. However, the limit states of use for these structural systems need to be analysed, with no doubt, in a more sensible way. In this way, willing to contribute to supply subsidies to the structural engineers, in the dynamic analysis of structures subject to excitation induced by human beings, several loads models are developed to represent the act of walking. The space and time variation of the dynamic load is considered through the analysis and the transient effect of the impact of the human heel on the floor is taken into consideration, as well. In this way, It is considered in this dissertation, several structural models associated to composite floors (steel-concrete). In this study, it was considered the usual techniques of discretization, based on the Finite Element Method (FEM) using the computer program Ansys. An extensive analysis concerning the dynamic response of the floors is made, by means of the application of the developed load models, mainly, in terms of the values of the accelerations. The results obtained are compared to those supplied by the techinical literature available about the subject with the point of view associated to the human comfort. It is also investigated, the influence of the structural parameter variation on the dynamic response of the models, such as: span length, damping ratio, thickness of the slab and, also, rigidity of the beam columns. The results obtained along the study clearly indicate that the structural designers must be alerted to important distortions that may occur when the project rules are used without the necessary caution. Another important remark is regarded to the fact that in several analysed floors it is observed that the criteria of human comfort are not satisfied which demonstrate the importance of the consideration of the dynamic effect caused by human beings in the analysis of this type of problem.

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / Atualmente, as novas tendências arquitetônicas e as exigências de mercado, vêm conduzindo a engenharia estrutural na busca por soluções cada vez mais arrojadas, as quais exigem grande experiência e conhecimento dos projetistas estruturais aliados a utilização de novos materiais e tecnologias. Esta filosofia de concepção estrutural está inserida em uma das mais importantes tendências de projeto dos últimos anos, ou seja: a busca por sistemas estruturais de rápida execução, dotados de peças de menor peso próprio e que possam vencer grandes vãos com um mínimo de elementos verticais, permitindo assim uma maior flexibilidade na adequação de ambientes. Por outro lado, esta filosofia de projeto tem conduzido a elementos estruturais cada vez mais esbeltos e com freqüências naturais cada vez mais baixas e, por conseguinte, mais próximas das faixas de freqüência das excitações dinâmicas associadas às atividades humanas, tais como: andar, correr, pular, etc. Devido as razões expostas no parágrafo anterior, os sistemas estruturais de engenharia tornaram-se bastante vulneráveis aos efeitos de vibrações induzidas por pequenos impactos como é o caso do caminhar de pessoas sobre pisos, resultando em desconforto para as pessoas. Deve-se destacar, ainda, que tais considerações de projeto têm atendido aos estados limites últimos. Todavia, os estados limites de utilização desses sistemas estruturais precisam ser analisados, sem sombra de dúvida, de maneira mais criteriosa. Deste modo, no sentido de contribuir para fornecer subsídios aos engenheiros estruturais, no que tange a análise dinâmica de estruturas submetidas a excitações induzidas pelos seres humanos, são desenvolvidos diversos modelos de carregamento representativos do caminhar das pessoas. A variação espacial e temporal da carga dinâmica é considerada ao longo da análise e, bem como, o efeito transiente do impacto do calcanhar humano nos pisos é levado em conta. Assim sendo, são considerados nesta dissertação diversos modelos estruturais associados a pisos mistos (aço-concreto). Técnicas usuais de discretização, com base no emprego do Método dos Elementos Finitos (MEF), via utilização do programa computacional Ansys, são consideradas neste estudo. Uma análise extensa acerca da resposta dinâmica dos pisos é feita, mediante o emprego dos modelos de carregamento desenvolvidos, principalmente, em termos dos valores das acelerações. Na seqüência, os resultados encontrados são comparados com aqueles fornecidos pela literatura técnica disponível sobre o assunto sob o ponto de vista associado ao conforto humano. Investiga-se, também, a influencia da variação de parâmetros estruturais sobre a resposta dinâmica dos modelos, tais como: comprimento vão, taxa de amortecimento, espessura das lajes e, ainda, rigidez das ligações viga coluna. Os resultados obtidos ao longo do estudo indicam, claramente, que os projetistas estruturais devem ser alertados para distorções importantes que ocorrem quando as normas de projeto são utilizadas sem o devido cuidado. Um outro importante diz respeito ao fato de que em diversos pisos analisados observa-se que os critérios de conforto humano não são satisfeitos, demonstrando a importância da consideração dos efeitos dinâmicos provenientes dos seres humanos na análise desse tipo de problema. / Nowadays, the new architectural tendency and the market requirements, are leading structural engineering in the search for bolder solutions, which demands great experience and knowledge of the structural designers associated to the use of new materials and technologies. This philosophy of structural conception is inserted in one of the most important trends of project of the last years that means: the search for structural systems of fast execution, endowed with parts of lower weight and that can be successfully large with a minimum of vertical elements, thus allowing a higher flexibility in the ambients adequacy. On the other hand, this project philosophy has lead to structural elements more and more slender and with natural frequencies much and much lower and, therefore, closer to the frequency of the dynamic excitation associated to the human beings activities, such as: walking, running, jumping, etc. Due to the reasons described in the previous paragraph, the structural engineering systems became sufficiently vulnerable to the effects of vibrations induced by small impacts as it is the case of walking of people on floors, resulting in discomfort to the people. It must be highlighted, also, that such project considerations have fulfilled the required limit states. However, the limit states of use for these structural systems need to be analysed, with no doubt, in a more sensible way. In this way, willing to contribute to supply subsidies to the structural engineers, in the dynamic analysis of structures subject to excitation induced by human beings, several loads models are developed to represent the act of walking. The space and time variation of the dynamic load is considered through the analysis and the transient effect of the impact of the human heel on the floor is taken into consideration, as well. In this way, It is considered in this dissertation, several structural models associated to composite floors (steel-concrete). In this study, it was considered the usual techniques of discretization, based on the Finite Element Method (FEM) using the computer program Ansys. An extensive analysis concerning the dynamic response of the floors is made, by means of the application of the developed load models, mainly, in terms of the values of the accelerations. The results obtained are compared to those supplied by the techinical literature available about the subject with the point of view associated to the human comfort. It is also investigated, the influence of the structural parameter variation on the dynamic response of the models, such as: span length, damping ratio, thickness of the slab and, also, rigidity of the beam columns. The results obtained along the study clearly indicate that the structural designers must be alerted to important distortions that may occur when the project rules are used without the necessary caution. Another important remark is regarded to the fact that in several analysed floors it is observed that the criteria of human comfort are not satisfied which demonstrate the importance of the consideration of the dynamic effect caused by human beings in the analysis of this type of problem.