Material and structure, being indivisible, provide the basis for this thesis exploration. The material of choice was concrete, inspired by the use of cast objects made in the studio. Through the act of form making and casting tectonic material integration developed. Intrinsic structural qualities of the material were affirmed with repeated drawing, form making and casting, while exploring the phenomenon of the transferred surface. An open urban site in Washington, DC was chosen before a building type was determined. Neighborhood and site analysis identified the potential need for a Firehouse. This building type allowed the opportunity to explore the use of concrete for vehicles as well as people. Can concrete, maligned for being cold and harsh, hold a building and its uses in comfort and beauty? / Master of Architecture / I struggled to find a direction for my Master of Architecture Thesis, like most, but knew materiality and tectonics would be the focus. After being enthralled with the annual WAAC Concrete competition, and the rampant use of ROCKITE in the Old Town studio I settled on formed concrete as a driver. An urban site was a given, an empty lot at 14th Street and V Street NW that seemed a managable size was perfect. Neigborhood and site analysis revealed the potential need for a Firehouse, in the pull-through style popularized by suburban stations.(1) This building type allowed many opportunities to explore concrete structural tectonics, for the human user and the automobile. Ideas of how concrete holds different materials, and how those relationships create a comfortable and useful space were examined in drawing and model.

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[pt] O futuro aponta para um crescente emprego do concreto de alto desempenho e da incorporação de fibras no concreto. O concreto de alto desempenho por suas maiores resistência e durabilidade e as fibras por conseguirem dar ductilidade e tenacidade aquele produto extremamente frágil. Recentemente foi publicada no Brasil a proposta de revisão da NBR6118, chamada de nova NB1. Nela novas relações constitutivas para o concreto estão indicadas, assim como foram modificados processos de dimensionamento. Neste trabalho foi feita a experimentação de três séries de vigas de concreto de alto desempenho nas quais foram incorporadas três tipos de fibras: aço, polipropileno e sisal. Nas peças da primeira série, a ruptura foi atingida por cisalhamento. Já as vigas das segunda e terceira séries foram concebidas de sorte a se atingir o estado limite último por flexão. Apresentam-se algumas considerações sobre o desempenho das vigas e a performance das fibras. Utiliza-se a formulação da nova NB1 para prever o comportamento das peças estruturais. Faz-se uma análise a respeito do esforço cortante resistente de cálculo e do momento fletor resistente de cálculo utilizando-se também expressões das normas Norueguesa, Canadense e Neo Zelandeza. Os resultados mostram que as fibras interferem pouco nos esforços resistentes nos estados limites últimos. As fibras de aço apresentaram ligeira e benéfica influência no esforço cortante resistente de cálculo. Também indicam que a formulação da nova NB1 pode em muitos casos ser adequada mesmo para concretos de resistência característica superiores a 50MPa, com e sem fibras. Em outros casos, como no dimensionamento ao esforço cortante, pode ser contra a segurança. As fibras de sisal promovem um esmagamento mais brando do concreto, apresentando um potencial que merece ser melhor investigado e explorado. / [en] The future is directed to an increasing use of high performance concrete reinforced with fibers. The former due to its improved durability and strength, and the latter due to its ability to give ductility and tenacity to such a fragile product. Recently reviewed draft of the NBR 6118, called new NB1, was published. New constitutive laws for concrete and design procedures were incorporates. In this work, three series of steel reinforced high performance concrete beams with three types of fibers steel,polypropylene and sisal) were tested. The first series of beams attained shear rupture. In the second and third series, the beams were reinforced so as to attain the ultimate limit state by flexure. The behavior of the beams subjected to two point loads is discussed. The formulation presented by new NB1 to foresee the behavior of the structural elements is used. An analysis concerning shear and flexural moment design is also made using the procedures from Norway, Canada and New Zeland codes. Results show that fibers have low influence on resistant shear and moment in the ultimate limit states. The steel fibers presented a slightly and beneficial influence on the resistant shear force. The results also show the new NB1 code may in several cases be adequate to concrete with strength reaching more than 50MPa, with or without fibers. In other cases, as in shear design, it can be against safety. The sisal fibers promote a soft crushing of the concrete, presenting a potential which deserves further investigation.

The purpose of this paper is to present the development and use of a computer program to perform an automated structural design of two dimensional static concrete structural systems. The structural systems considered herein are composed of reinforced concrete beams and columns connected by rigid joints. Structural systems composed of large numbers of joints and members may be analyzed by using the developed program. The paper presents the development of the structural analysis using the displacement method and matrix techniques and the development of the concrete axial-moment interaction criteria. This criteria is based on the ultimate strength design using the 1971 ACI Building Code requirements. A detailed sample problem of a four story concrete building structure is presented. The sample problem gives the details of computer program input and output. The presented computer program is written FORTRAN language.

What will our future cities, public buildings or homes look like and how will they be constructed? Given the climate challenges of today it is clear that we cannot continue to waste material in the same pace as we have done historically, and one way to reduce the impact on the environment is to keep the materials in use for as long as possible. We all know that concrete has a high impact on the environment and it is actually the second most used substance in the world after water, and the most widely used building material by far. Obviously it is best to never demolish buildings but in cases where demolition or major alterations is necessary, reuse of the building material is key for a sustainable industry. This will have an impact on how buildings are demolished, designed and built. For this diploma project explores what would happen if we instead of crushing obsolete concrete structures could cut them into smaller pieces and build something new out of it.

The application of a mineral admixture, or a corrosion inhibitor, or a combination of both are methods used for the corrosion protection for reinforced concrete bridges. The results of a study on evaluation of corrosion inhibitors from three different manufacturers and of concretes with fly ash, slag cement, and silica fume and a concrete with silica fume and a corrosion inhibitor are presented. The specimens were built to simulate four exposure conditions typical for concrete bridges located in the coastal region or inland where deicing salts are used. The exposure conditions were horizontal, vertical, tidal, and immersed zones. The specimens were kept inside the laboratory and were exposed to weekly ponding cycles of 6% (w/w) sodium chloride solution. In addition, cover depth measurements from 21 bridge decks and chloride data from 3 bridge decks were used, together with laboratory data, in modeling the service lives of the investigated corrosion protection methods. The methods used to assess the condition of the specimens included chloride concentration measurements, corrosion potentials, and corrosion rates (3LP). Additionally, visual observations were performed for identification of rust stains and cracking on concrete surfaces. Modeling the time as a function of probability of the end of functional service life (EFSL) is presented. It has been shown that the distributions of surface chloride concentration, C0, and diffusion coefficient, Dc, are key elements in the model. Model predictions show that the concretes with mineral admixtures provide much better level of protection against moisture and chlorides than the ordinary portland cement concrete alone. Application of a corrosion inhibitor causes an elevation of the chloride threshold resulting in an additional increase in time to EFSL. More field studies are needed to better estimate distributions of surface chloride concentration and diffusion coefficient of Virginia bridge decks, and to confirm predicted times to EFSL for low permeable (LP) concretes. / Ph. D.

Corrosion on bridges is a common issue since it can be caused by multiple agents such as marine environments or deicing chemicals. The damages caused by these agents, if left unmitigated, may lead to failure of the superstructures. If corrosion is present in the end regions of the beams, failure of the girders will likely be in shear, which is a sudden failure mode and not the preferred limit state. Therefore, it is beneficial to study repair practices and their advantages, as repairs are often more cost-effective than building entirely new structures. Repairing prestressed girders for shear is not common practice, but with the number of superstructures considered structurally deficient in the United States, additional consideration should be given to repair methods. In this study, two beams were extracted from two decommissioned bridges and were repaired using Carbon Fiber Reinforced Polymer (CFRP) to investigate how well proposed repairs functioned. One of the beams is an American Association of State Highway and Transportation Officials (AASHTO) Type II beam, while the second one is an adjacent box beam. Before repairs were done, the beams had their ends further damaged with accelerated corrosion induced via electrolysis to ensure that the beams would have enough deterioration in their shear span to simulate the worst-case scenario found in the field. Afterwards, the girders had their damage and residual strength estimated, and repairs were designed using guidelines from the American Concrete Institute (ACI) and AASHTO for CFRP repairs. Since the adjacent box beam could only be repaired in flexure, it failed in shear with a load similar to previous studies done in beams from the same bridge, which indicates that repairs for box beams need further investigation. The repairs on the AASHTO Type II beam worked well for shear, and both ends failed in flexure, which is an improved failure mode since failing in flexure is more ductile and predictable than shear failures. One end of the AASHTO Type II beam failed by concrete crushing and CFRP rupturing, and the other end failed by strand rupturing, which shows that the accelerated corrosion worked as was predicted. / Master of Science / Corrosion on bridges is a major problem across the United States, especially in marine environments and in cold areas where deicing chemicals are needed to ensure the safety of the drivers. These external agents typically accelerate the deterioration of bridges and lead to expensive repairs and sometimes total replacement of structures. In order to study repair methods for bridges that have been exposed to corrosive agents, bridge girders were extracted from two decommissioned bridges in Virginia. The level of damage in these girders was assessed and it was determined that more corrosion had to be induced into the girder to ensure repairs were needed. After that process, the strength of the girders was estimated using guidelines from the American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO), and the girders were repaired for shear using sheets of Carbon Fiber Reinforced Polymers (CFRP). These repairs were done by using two different wrapping schemes, one that enveloped the sides of the girder, and one that was only at the bottom of the girder. The girders then had their ends tested under three-point bending to evaluate the effectiveness of the repairs. The girder that had the sides repaired as well performed better since the failure mode of it changed from shear to flexure. The girder that only had its bottom repaired did not do as well since its failure mode was still shear.