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The adverse effects of contaminated outdoor air have been recognized and subject to control for many years. More recently environmental engineers and health professionals have become cognizant of the hazards associated with contaminated indoor air. It is now understood that contaminated indoor air negatively impacts human health, worker productivity, and physical property. Volatile organic compounds (VOCs) are a common class of indoor air pollutants. Building materials such as treated wood, pressed-wood products, wallboard, sealants, adhesives, floor coverings, and paints can be sources of VOC emissions. The knowledge-base necessary to develop effective solutions to indoor air quality problems requires an understanding of the emissions behavior of indoor materials. Environmental chambers are often utilized to characterize indoor material as sources of VOC emissions to indoor air. Chamber studies, although expensive and time consuming, can be utilized to provide estimates of the rates at which a particular material emits VOCs under a specific set of environmental conditions. By fitting curves to emissions data obtained through chamber studies, VOC emissions models have been constructed. These models are frequently empirical and as a consequence, 1) apply only to the specific material and environmental conditions investigated, 2) provide little understanding of the source/sink characteristics of the material, and 3) provide little knowledge of the mass transfer processes governing emissions behavior. As a result, our understanding of the mechanisms that control VOC emissions from indoor materials remains rudimentary. Physically-based models that describe the emissions characteristics of building materials would greatly facilitate the process of improving indoor air quality. Evidence exists suggesting well-established fundamental mass transfer mechanisms govern emissions from indoor materials. Of the various mechanisms governing emissions behaviors, diffusion appears to be one of the most significant. The primary objective of this research was to demonstrate that the VOC emissions source behavior of a diffusion-controlled homogenous building material could be predicted using a mechanistic mathematical model. A commercial grade sheet vinyl flooring (VF) was selected for study because VF is present in many residential and commercial buildings, is relatively homogenous, and has been shown to emit hazardous organic chemicals. If successful, this research would demonstrate that the proposed strategy could be generalized to other VOC sources using appropriately constructed mathematical models. Satisfying the research objective required development of a physically-based model to predict gas-phase VOC concentrations resulting from exposure to a diffusion-controlled material. Key parameters for this model are the solid-phase diffusion coefficient, D; the solid/air partition coefficient, K; and the initial solid-phase VOC concentration, C0. D and K have been previously quantified for only a few indoor materials and methods for determining C0 are rudimentary. Therefore, this research project required development and execution of methods for quantifying D, K, and C0. D and K were quantified using a recording microbalance. C0 was evaluated using a new technique of cryogenic milling followed by fluidized bed desorption. The model was validated by exposing a VF sample in an environmental chamber and directly measuring gas-phase VOC concentrations resulting from mass transfer from the solid material. Further model validation was achieved by directly measuring the VOC concentration profiles after exposure in environmental chambers. Because the key model parameters were quantified independently of chamber studies, the model validation process provided a rigorous test of the validity of the mass transfer model in particular and of the source characterization strategy in general. The results of this research contribute to our understanding of the fundamental mechanisms that govern emissions of VOCs from vinyl flooring and provide a sound theoretical foundation for characterization of a wide range of other sources of indoor VOCs. This understanding could facilitate product reformulation strategies aimed at preventing or reducing indoor air contamination. Mass transfer models could also be utilized to develop standards for the environmental performance of indoor materials. The proposed approach will prove useful in conjunction with broader studies on sick building syndrome to identify sources that may have a critical impact on the health and comfort of building occupants. / Ph. D.

For decades engineers have been concerned with finding ways to reduce the dead load of a buildings structural system. This thesis investigates the potential of reducing the dead load of a structure by creating new lighter-weight floor systems using various configurations of mixed materials. Floor systems have a/ways been one of the heaviest components of a buildings structural system, and therefore comprise a significant portion of the structures dead load. As a result, by developing a substantially lighter-weight floor system it should be possible to reduce the entire weight of a buildings structural system, from the framing members down to the foundations. This paper presents some alternatives that might be considered in designing these lightweight floors. / Master of Science

This thesis presents the results of an extensive study of several types of lateral bracing for solid-sawn and parallel-chord truss floor systems. Three solid-sawn floor bracing systems were evaluated: X-bridging, full-depth solid blocking, and finally, post-tensioned solid-blocking. Five different truss bracing systems were investigated: bottom-chord bracing, steel X-bracing, strong-back bracing, and the bracing combinations of X-plus bottom-chord bracing, and strong-back plus bottom chord bracing were evaluated. A total of seven, 4.9m x 4.9m floor specimens were constructed. Four 38 x 286 mm (2 x 12 inch nominal), solid-sawn wood joist floors were constructed for evaluation of the solid-sawn bracing systems. Three 305 mm (12 inch) deep, bottom-chord bearing, metal plate connected, parallel-chord truss floors were constructed to evaluate the truss floor bracing systems. Both floor systems utilized joist/truss spacings of 610 mm (24 inches) on center, and were covered with 18.3 mm (23/32 inch) thick, tongue-in-groove, plywood sheathing. The bracing systems were evaluated at different live load levels and boundary conditions. The bracing systems were subjected to both static and dynamic loadings. The effect of the bracing systems were determined based on four parameters: one static, and three dynamic. The percent change in concentrated load carried by the loaded joist was used as the static test parameter. The effect, if any, of the bracing systems on the modal resonant frequencies, separation of frequencies, and damping characteristics of the floor systems, were used as dynamic parameters. Future research and design recommendations were given in the conclusion chapter. / Master of Science

No description available.

A aplicação de um piso de madeira maciça sobre um contrapiso de concreto dá origem a um sistema que une dois materiais com diferentes características higroscópicas, e no qual a movimentação da umidade é ainda um fenômeno pouco conhecido. Visando um melhor entendimento desse fenômeno, a presente pesquisa buscou avaliar diferentes equipamentos para medir o teor de umidade do concreto, desenvolver uma metodologia para quantificar a água evaporável presente no substrato mineral e, a partir desses resultados, sugerir o teor de umidade do substrato mais adequado à aplicação de um revestimento de madeira. Corpos de prova de concreto, preparados com traço 3:1:1 e relação água cimento em torno de 0,5, foram submetidos a secagem ao ar, sendo que a variação do teor de umidade do concreto ao longo do tempo foi acompanhada pela perda de massa e com a utilização de medidores elétricos de umidade do tipo resistência e de contato.. Com o auxílio da análise de regressão foi possível estabelecer equações de correção para as leituras de umidade dos aparelhos. Para a quantificação da água evaporável no concreto, foi desenvolvido um corpo de prova utilizando-se cilindros de MDF com 6,0 cm de comprimento e 4,8 cm de diâmetro, inseridos em tubo de PVC e com uma das extremidades vedada com filme plástico e silicone. O cilindro de MDF mostrou-se um indicador eficiente da presença de água evaporável no concreto, uma vez que as taxas de adsorção pelo MDF puderam ser diretamente correlacionadas às taxas de evaporação pelo concreto. O efeito do adesivo no sistema concreto-madeira foi avaliado através da variação do gradiente de umidade em madeira de Jatobá (Hymenaea sp). Tacos de Jatobá, com dimensões de 100 mm x 80 mm x 18 mm e nos quais foram colocados sensores a 4 mm e a 17 mm de profundidade, foram colados em corpos de prova de concreto utilizando-se adesivo a base de PVA com 60% de sólidos. Os resultados mostraram que a água contida no adesivo não foi totalmente adsorvida pelo taco e o gradiente de umidade no sentido da espessura apresentou relação com o teor de umidade à profundidade de 17 mm, confirmando a hipótese de que existe um fluxo de umidade na interface concreto-madeira. / The application of solid wood flooring over a concrete subfloor originates a system joining two materials with different hygroscopic characteristics, and in which the moisture movement still is a little known phenomena. Looking for the better understanding of moisture relationship in this system, the present research evaluated different equipments to measure concrete moisture content, to develop a methodology to quantify the vaporizable water present in the mineral substrate and, according to these results, to suggest the substrate moisture content more adequate to application of a wooden covering. Sample test of concrete, prepared with trace 3:1:1 and relation water/cement around 0.5, were submitted to air drying and the variation of the concrete moisture content during the process was registered by the mass loss and with the use of electric moisture meters of resistance and contact types. Through regression analysis it was possible to establish equations to correct moisture meters readings. To quantify the vaporizable water present in concrete, a sample test was developed using cylinders of MDF with 6.0 cm of length and 4.8 cm of diameter, inserted in a PVC tube and with one of the extremities closed with plastic film and silicone. The MDF cylinder was an efficient indicator to quantify vaporizable water in the concrete, considering that the moisture adsorption rate of MDF samples could be directly correlated to the concrete evaporation rate. The effect of adhesive in concrete-wood system was evaluated through the variation of moisture content gradient in Jatobá lumber (Hymenaea sp). Flooring samples of Jatobá, with dimensions of 100 mm x 80 mm x 18 mm and moisture sensors inserted at depths of 4 mm and 17 mm, were glued to concrete sample test using a PVA based adhesive with 60% of solids. Results showed that the water contained in the adhesive was not totally adsorbed by the flooring sample and the moisture gradient across sample thickness is correlated to moisture content at depth of 17 mm, what confirm the moisture flow between concrete and wood.

Fall-related injuries in adults over the age of 65 pose an important public health issue especially with an increasing number of older adults living in retirement homes and nursing homes. Safety floors have been developed as an intervention to reduce the risk of these injuries. However, their effects on balance control reactions had never been tested during certain activities of daily living in retirement home dwellers. This research investigated how balance reactions are affected by the mechanical properties of safety flooring in older adults. The safety flooring showed minimal impact on the balance reactions while retaining force attenuation properties. There were two studies as part of this thesis. The purpose of the first study was to determine whether the Nintendo Wii Balance Board (WBB) can be used as an appropriate substitution for a force plate when measuring balance reactions during common tests used to assess balance in older adults. Specifically, I characterized the technical specifications of the WBB and compared them to those of the force plate, showing that the two devices yielded similar responses during balance measures of quiet stance. The second study investigated the effect of two traditional floors and three safety flooring systems on balance control mechanisms (based on changes in underfoot centre of pressure) during sit-to-stand and quiet stance tasks in retirement home-dwellers. The results of this study provided evidence supporting the potential for safety floors to reduce fall-related injury risk without impairing balance and mobility of users. Additional research may want to assess WBB performance during dynamic tasks involving shear forces. The results from this study supports prospective clinical investigations of pilot installations of safety flooring in retirement and nursing home settings to evaluate their real life effects on fall related injuries.

This dissertation involved a theoretical and experimental investigation of the adhesive forces between spherical particles of four different diameters and two selected flooring materials under different air velocities. Previous theoretical work and experiments described in the literature tended to be conducted with idealized surfaces, and therefore have limited applicability to indoor environments. Controlled experiments were designed, constructed and executed to measure the air velocity required to overcome adhesion forces. The diameters of the particles investigated were 0.5, 3.0, 5.0 and 9.9 [mu]m, and the flooring materials were linoleum and wooden flooring. The critical velocity, the flow at which 50% of the particles detached, is presented as a function of particle diameter for each surface. The measured values were then compared to empirical and theoretical models as well as to a scaling analysis that considers component forces that act on a particle-surface system. The results suggest that critical velocity decreases with increasing particle diameter and that existing models have limited applicability to resuspension from flooring materials. / text

Fall-related injuries in adults over the age of 65 pose an important public health issue especially with an increasing number of older adults living in retirement homes and nursing homes. Safety floors have been developed as an intervention to reduce the risk of these injuries. However, their effects on balance control reactions had never been tested during certain activities of daily living in retirement home dwellers. This research investigated how balance reactions are affected by the mechanical properties of safety flooring in older adults. The safety flooring showed minimal impact on the balance reactions while retaining force attenuation properties. There were two studies as part of this thesis. The purpose of the first study was to determine whether the Nintendo Wii Balance Board (WBB) can be used as an appropriate substitution for a force plate when measuring balance reactions during common tests used to assess balance in older adults. Specifically, I characterized the technical specifications of the WBB and compared them to those of the force plate, showing that the two devices yielded similar responses during balance measures of quiet stance. The second study investigated the effect of two traditional floors and three safety flooring systems on balance control mechanisms (based on changes in underfoot centre of pressure) during sit-to-stand and quiet stance tasks in retirement home-dwellers. The results of this study provided evidence supporting the potential for safety floors to reduce fall-related injury risk without impairing balance and mobility of users. Additional research may want to assess WBB performance during dynamic tasks involving shear forces. The results from this study supports prospective clinical investigations of pilot installations of safety flooring in retirement and nursing home settings to evaluate their real life effects on fall related injuries.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.