The development of high strength, light weight materials has generated more efficient designs of steel joist-concrete slab floor systems. Though the structural integrity is rarely compromised, these floor systems are more susceptible to human-induced vibrations which may be annoying to the occupants of the structure. The purpose of this investigation was to develop methods of improving the vibration characteristics of joist-supported floor systems. The frequency and first maximum amplitude of vibration can be altered by redesigning the cross-section of the floor system in order to improve its acceptability. However, damping has the greatest effect on the perceptibility of occupant-induced floor vibrations. Therefore, this study focussed on devising methods of increasing damping in joist supported floor systems. Steel joist-metal deck-concrete slab test floors were constructed for the purpose of this investigation. In addition, a two-bay building was constructed so that the developments of this research could be field tested. The experimental results were presented and recommendations were made for future work in this field. / Master of Science

Four aspects influencing the vibration characteristics of steel member supported floors were investigated. The four aspects are: 1) the number of tee-beams effective in resisting a heel-drop impact for steel joist and steel beam-concrete slab floors, 2) the effective moment of inertia of steel joist and joist-girder members, 3) the ability of joist seats to provide composite behavior between the supporting member and overlying slab, and 4) the effects of extending and restraining the bottom chords of joist members. A new equation was developed to predict the number of effective tee-beams. The proposed equation is recommended to replace the two current equations. The proposed equation is a regression equation based on the results of a finite element analysis of 240 floor systems and is considered to be more accurate than the current equations. Next, a study was undertaken to determine the relationship between the span-to depth ratio of a joist or joist-girder member and it's effective moment of inertia. Twenty five joists and joist-girders were modeled and analyzed using the finite element method and their effective stiffnesses calculated. The effective stiffness of each member was plotted against the respective span-to-depth ratio. A linear regression line was then fit to the data to mathematically represent the trend. Finally, a vibration test floor was constructed to investigate the joist seat behavior and extended bottom chords. Finite element models were developed and analyzed and frequency and stiffness tests were performed to evaluate the floor's behavior. Conclusions were then drawn and recommendations made concerning the joist seat behavior and the effects of extending joist bottom chords. / Master of Science

Advancements in design technology and construction materials have allowed composite floor systems to become longer and shallower. As a result, serviceability considerations rather than strength considerations have started to control designs. Partial continuity in composite floor systems has been suggested as a means by which the serviceability aspects could be improved. A new beam-to-girder connection referred to as a composite semi-rigid beam-to-girder connection is investigated as a possible method to provide partial continuity in floor systems. Four of these connections are evaluated experimentally and analytically to determine their behavior and the feasibility of their use in typical composite floor systems. The results indicate that these connections would improve serviceability aspects of the floor system and would improve the general efficiency of the floor design. / Master of Science

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). "July 2009." Includes bibliographical references. Also available via the World Wide Web.

A fully automated computer program is developed for the optimum design of steel space trusses acting compositely with a concrete slab placed on top. The program sizes the truss members to meet the requirements of the load and resistance factor design specification of the American Institute of Steel Construction using the load combinations of ANSI. Earthquake loading is not considered. The optimum size is based on minimum cost, regarding the amount of welding required at the joints and of the member itself. The total cost is based on all steel work in the truss. Once the truss configuration has been defined, and it has been ensured that linear elastic behavior exists, the structure is analyzed for the construction process, to make sure that no overstressing will take place in any structural element at any time during construction and service. The analysis and design principles are presented and an actual design case is solved. (Abstract shortened with permission of author.)

<p>Nowadays there are several contaminated buildings that receive a new field of application. These buildings used to have industrial activities which contaminated the buildings with both organic and inorganic pollutants that can cause serious health problems. Now these buildings get new functions like office work, school buildings or daycare centers. But before these buildings can be used as for instance schools some kind of remediation has to be carried out to remove the contamination. The aim with this report was to make an inventory of available methods for remediation of contaminated buildings and to evaluate the result of some performed remediations. The buildings that were investigated in this report were contaminated with organic pollutants. This report includes a summary of the legislation that concerns contaminated buildings, health problems that solvents and oils can cause and information of available methods for remediation of polluted buildings. A survey was made and property holders of remediated contaminated buildings answered it. According to the survey it emerged that air-regulated floors and new floor constructions were the most commonly used methods for remediation. The choice of method was often a balance between time and economy. After the remediation it’s important to do inspections to make sure that the remediation had removed the contamination. Inspection can be made by measuring the indoor air. Another way to inspect a remediation is to send out surveys to those people who stay in the building. The most important aspect during the remediation is to guarantee peoples health. Results from the survey showed that air-regulated floors are a good remediation method and often used with good results. To make the remediation work easier generic guideline values for different building materials should be developed to be used in the analysis of the degree of the remediation.</p>

Approved for public release; distribution in unlimited. / With the introduction of wireless Local Area Networks (WLANs) in many organizations, it became much easier to intercept confidential files and personal health records. The present study focused on radio frequency propagation in a high-rise building, specifically, the attenuation between floors, and the possibility of intercepting signals through the floors. The current work is based on simulations using the Urbana software tool. It is used to predict the contour of the power levels of signals for a given physical model of the environment using high-frequency ray-tracing methods. The simulation results indicated that the signal levels for a 1 W transmitter could only be detected at the -70 dBm level within two floors (above or below). Even within the two floor range the signal distribution was very nonuniform due to the effects of multipath. The results indicated that closing doors reduced the signal levels, but only slightly for wood doors. Signals escaped the building through the window and were able to travel between floors via this path. The ray tracing accounted for only single diffraction, and therefore rays diffracted two or more times were not included. / Captain, Tunisian Air Force

As estruturas de concreto pré-moldado tendem a ser mais moduladas e mais padronizados do que as estruturas de concreto moldadas no local, logo as técnicas de otimização podem produzir mais benefícios econômicos devido à produção em escala. Entre as técnicas de otimização utilizadas em engenharia estrutural, os algoritmos genéticos têm sido reconhecidos como uma forte tendência devido à sua facilidade de implementação e os excelentes resultados obtidos. Este trabalho trata da otimização integrada de pavimentos de edifícios com estruturas de concreto pré-moldado utilizando algoritmos genéticos e minimizando os custos. O principal objetivo é apresentar uma formulação para a otimização do pavimento, baseado em restrições arquitetônicas; restrições estruturais e restrições construtivas. A função-objetivo contemplou não só o consumo de materiais, mas também os aspectos relativos à fabricação, transporte e montagem. Atesta-se a consistência da representação do problema pelo modelo em função dos resultados que foram muito coerentes com a prática dos projetos. Os vários exemplos apresentados mostraram a robustez e a aplicabilidade do modelo e evidenciou-se a possibilidade de sua utilização em um sistema de apoio à tomada de decisão, que sirva como ferramenta de auxílio aos projetistas na concepção estrutural. Foi implementada a rotina dos transgênicos, que melhorou a convergência, e, a dos gêmeos, que aumentou a variabilidade da população. / The precast concrete structures are more modular and standardized than the cast in place concrete structures, therefore optimization techniques can improve economics gain because of series production. Among the optimization techniques in structural engineering design, genetic algorithms have been recognized as a trend. This work aims the floor precast concrete building optimization using GA\'s and minimizing the cost. The main goal of the work is to present a model to optimize the floor taking account of the structural, architectonics and constructive restrictions. The adopted model reached its purpose of the representing the more realist as possible the problem. The cost function considered not only the material consumption but the manufacture, transport and assembled stage. An integrated structural optimization is performed from the structural layout (columns position, directions and spans for beams and hollow cores) through the complete elements detailing (dimensions and reinforcement). The example results evidence the effectiveness of the formulation, they were very consistent with the design practice and they present the system application possibility like a decision support system that helps the engineer in the projects development. It was implemented a transgenic routine to improve the convergence and a twin routine to improve the variability of the population.

No contexto da modernização da construção civil, a aplicação de elementos estruturais de concreto pré-moldado nas construções oferece comprovados benefícios à estratégia de execução das obras, dentre os quais se destacam o atendimento a vãos relativamente grandes, rapidez de montagem, leveza e excelente qualidade dos elementos que compõem a estrutura. Tratando-se especialmente do comportamento dinâmico das estruturas de concreto, os elementos pré-moldados, por apresentarem diversas situações transitórias de solicitação, devem ser avaliados quanto aos efeitos dinâmicos decorrentes da sua produção, transporte, montagem, execução das ligações, finalização da obra e uso. Considerando, nesse contexto, que a protensão é um recurso frequentemente utilizado nos elementos, evidencia-se a necessidade de estudos sobre a sua influência nos parâmetros dinâmicos. Em particular, elementos pré-fabricados protendidos, tais como painéis tipo duplo-T e lajes alveolares, têm sido muito utilizados em pisos de edifícios, todavia e não raras vezes sem uma prévia análise dinâmica quanto à vibração e ao atendimento aos limites de vibração em serviço. O presente trabalho apresenta uma síntese dos procedimentos de cálculo e verificação indicados por normas técnicas do Brasil e do Exterior para a avaliação do conforto humano quanto a vibrações excessivas, assim como os métodos analíticos empregados na determinação da frequência natural de um elemento estrutural, seja ele protendido ou não. Efetuou-se um estudo comparativo dos resultados analíticos com os de uma simulação numérica de painéis duplo-T e lajes alveolares, feita com programa computacional ANSYS, baseado no Método dos Elementos Finitos, sendo eles discutidos quanto ao Estado Limite de Vibrações Excessivas (ELS-VE). Este trabalho apresenta também um estudo experimental sobre um modelo físico de viga de concreto protendido com cabos externos, com o objetivo de demonstrar a aplicação de técnicas de caracterização dos parâmetros dinâmicos e discutir eventuais soluções para o controle ou atenuação de vibrações excessivas. Essa viga foi também analisada numericamente com o programa computacional ANSYS e feita a comparação dos resultados experimentais e numéricos. Conclui-se que, do ponto de vista do ELS-VE, os painéis duplo-T e lajes alveolares particularmente analisados são passíveis de restrições a partir de certos vãos e que, sob determinadas condições ora discutidas, o emprego de tirantes externos, protendidos ou não, podem ser aplicados no controle de vibrações, seja por aumento da rigidez do sistema viga-tirante, seja pelo controle da fissuração do concreto. / In the context of construction modernization, the application of precast concrete elements offers a good and reliable alternative in the construction strategy, among them large spans, fast assembly, lightweightness and excellent structural members quality. Dealing about dynamic behavior of concrete structures, precast elements are subjected to several loading conditions, from their manufacturing, transport, assembly, connection and finally to service. Prestressing technique is often applied in precast elements, so the influence of prestressing forces on dynamic parameters must be considered. Precast prestressed concrete elements, such as double-T panels and hollow core slabs are commonly used in building floors, but not always a previous dynamic evaluation is accomplished, so vibration problems are likely to occur. This work presents a synthesis of design procedures as recommended by the brazilian and foreign codes regarding to human comfort under vibration conditions. Analytical methods allow the determination of natural frequency of structural elements, being them prestressed or not. Also typical double-T panels and hollow core slabs were analyzed by Finite Element Method (ANSYS software) and analytical and numerical results were compared. A discussion of the results about the Service Vibration Limit State is made. This work also presents an experimental study on a reinforced concrete beam provided with external prestressing tendons. The goal of this study was to demonstrate dynamic tests to characterize dynamic parameters and to discuss vibration control. The tested beam was also simulated on ANSYS to compare theoretical and experimental results. Some conclusions has been drawn, such as typical double-T panels and hollow core slabs may suffer restrictions above certain span dimensions. Also the application of external tendons, with or without prestressing forces may be applied to reduce vibration levels, either by increasing stiffness of the structure or controlling cracking of the concrete beam.

Nos últimos anos, inovações e desenvolvimentos importantes ocorreram na engenharia estrutural. Apesar disso, a maioria dos avanços não considera a natureza aleatória das variáveis. Partindo-se dessas idéias, apresenta-se uma contribuição na análise da segurança e confiabilidade em pavimentos de edifícios, introduzindo-se conceitos probabilísticos e estatísticos aplicados dentro de um modelo de comportamento não-linear para o concreto armado (Ghali & Favre). A resistência à compressão do concreto e os deslocamentos nas vigas e nos pavimentos são considerados como variáveis aleatórias, seguindo uma distribuição de probabilidade conhecida. O objetivo é relacionar valores da resistência característica à compressão do concreto (fck) e do módulo de elasticidade do material com determinados níveis de confiabilidade, expressos pelo índice &#946 e pela probabilidade de falha da função de estado limite escolhida. Objetiva-se analisar o comportamento das variáveis básicas e a interação entre elas, procurando avaliar, quantitativamente, a margem de segurança obtida com a aplicação de critérios de projeto da NB-1 e do EUROCODE. Pretende-se ainda fazer algumas considerações sobre a necessidade de se estudar a formulação de um coeficiente de minoração da resistência do concreto &#947c como função das variáveis básicas dos modelos empregados e de suas distribuições de probabilidade. / In the last years, important developments and innovations took place in the structural engineering context. In spite of that, most of that progress does not consider the random nature of the involved variables. Based on these aspects, a contribution to the safety and reliability analyses for building floors is presented. It is also introduced probabilistic and statistic concepts, applied to a well-known non-linear models for the reinforced concrete elements (Ghali & Favre). The concrete compression strength, as well as beam and floor displacements are assumed random variables, following a known probability distribution. The aim of the work is to relate the concrete characteristic strength in compression (fck) and the Young\'s modulus with certain levels of reliability, expressed by the &#946 index and by the failure probability of the limit state function. The behaviour of the basic variables and their interactions are analysed in order to evaluate the safety reached by applying NB-1 (Brazilian code for reinforced concrete structures) and EUROCODE design recommendations. Moreover, some comments are made on the future studies required to achieve a single reduction coefficient &#947c for the concrete strength, which may be given in terms of the basic variables of material models and their probability distributions.