<div>Pack rust or crevice corrosion is a type of localized corrosion. When a metal is in contact with a metal, or even non-metal, the metal starts to corrode, and rust starts to pack in between the surfaces. When signicant development of pack rust occurs, it can cause overstressing of bolts and rivets causing them to fail, and it can bend connecting plates and member elements thus reducing their buckling capacity. Thus it is important to mitigate the formation and growth of pack rust in bridges. This study was conducted to determine if pack rust occurs frequently and thereby may pose a problem in the state of Indiana. The study is divided into three primary tasks.The rst part of the study involves understanding the parameters involved in the initiation process of crevice corrosion and post-initiation crevice corrosion process. The second part of the study involves reviewing existing mitigation strategies and repair procedures used by state DOTs. The third part of the study involves identifying steel bridges with pack rust in Indiana. Analyses were performed on the data collected from Indiana bridges that have pack rust. This involved nding the components and members of bridges which are most aected by pack rust and nding parameters which in uence the formation of pack rust. Pack rust in the steel bridges were identied using the INDOT inspection reports available through BIAS system. The study revealed that good maintenance practices helped in reducing pack rust formation. The study identied locations on steel bridges which have a high probability towards pack rust formation. A mitigating strategy possessing qualities which can show promising results is identied.</div>

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Bridges in the US are severely damaged or suffer collapse from fires at significant rates, even when compared to other hazards such as earthquakes. Fire-induced bridge collapses are perpetuated by the general lack of installed fire protection systems. Therefore, new materials and applications are needed to mitigate structural damage that can be caused to civil infrastructure by severe fires. Accordingly, the objective of this study is to further the development of new fire protection applications in transportation structures. Specifically, the investigation centers on the development of new applications in passive fire protection materials, within the context of shielding steel-girder bridges against severe fire effects. A steel-girder bridge has been selected for study, and a high-resolution finite element model has been formed based on the corresponding bridge structural drawings. Temperature-dependent structural material properties and thermal properties have been synthesized and incorporated into the model. Additionally, a representative fire scenario has been formed (in part) based on a recent fire incident that occurred at the selected bridge site. The fire scenario also incorporates the characteristics of a fully loaded gasoline tank truck fire, where a means of incorporating the severe fire into the finite element model (as thermal loading) has been identified and enacted. Coupled thermal-mechanical finite element analyses have been carried out using the (unprotected) steel-girder bridge model. An additional finite element simulation has been carried out, where the steel-girder bridge model has been fitted with a refractory cement material that insulates the underside of the bridge spans. Also, a finite element simulation has been carried out where the steel-girder bridge model has been fitted with intumescent coating material as insulation against fire effects. Both the refractory cement and the intumescent coating materials have been found to possess robust insulation characteristics from the simulation results. Namely, the finite element analysis results indicate that, in the event of a bridge fire, both materials are capable of preventing the buildup of damaging temperatures in underlying structural members. Accordingly, the refractory cement and intumescent coating materials have been identified as successful passive fire protection materials for the fire scenario and bridge case considered.

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Orientador: Nilson Tadeu Mascia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil e Arquitetura / Made available in DSpace on 2018-08-12T06:32:42Z (GMT). No. of bitstreams: 1 Sartorti_ArturLenz_M.pdf: 8739751 bytes, checksum: b8c521a2573d5e6622b0d27a97dc444a (MD5) Previous issue date: 2008 / Resumo: A existência de um grande número de pontes com problemas patológicos importantes motiva a pesquisa sobre este assunto. As pontes de pequeno e médio porte têm relevância significativa para o desenvolvimento econômico e social do país, pois devem assegurar o trânsito de pessoas, veículos e matérias primas e escoamento dos produtos gerados. No entanto, o estado precário em que se encontra grande parte das pontes em vias urbanas e rurais, dificulta o deslocamento, causando desconforto e insegurança aos usuários. Além disso, elevam-se os custos de transporte para os produtores e de manutenção para as prefeituras. Diante desta realidade, busca-se nesse trabalho, avaliar o estado de conservação de pontes de pequeno e médio porte em vias urbanas e rurais na região de Campinas (SP). Desta forma, um correto embasamento teórico do assunto permitirá a adoção da acertada atitude frente a um quadro patológico. Sendo assim, esta pesquisa foca uma ampla revisão bibliográfica abrangendo o estado-da-arte do projeto de pontes e da identificação das patologias nas estruturas metálicas, de concreto armado e/ou protendido e de madeira, e também visa estabelecer conceitos que serão aplicados quando da escolha do método corretivo. Além do embasamento teórico, buscou-se constatar "in loco" a manifestação de patologias em nove pontes na região do município de Campinas (SP), apresentando-se sugestões quanto à profilaxia e correção em cada caso. Para colaborar com as sugestões, foram desenvolvidos dois projetos de pontes tipo anexados à pesquisa, os quais são de estruturas mistas de aço-concreto e de madeira. Finalmente observa-se a partir da presente pesquisa, que existe a necessidade de um mapeamento rigoroso das pontes urbanas e rurais com vistas de elevar a vida útil e garantir maior segurança à sociedade. / Abstract: The existence of a great number of bridges with pathological problems motivates the research on this subject. The small and medium bridges have a main importance to the economic and social development of the country, due to they must guarantee the people, vehicle, and raw material transit and the flow of manufacture products. However, the precarious condition that a great part of the bridges is in the city and in the rural area and has difficult the movement, causing discomfort and insecurity to people. Besides, there is an increase of the cost of transport to the producer and of the maintenance to the town hall. In the presence of this reality, this work intends to evaluate the conservation state of small and medium bridges in the city and in the rural area in the region of Campinas (SP). Thus, a consistent theoretical base about this subject will permit to choose a right attitude on a pathological way and this research focuses on a complete review of bibliography covering the state-of-art of the bridge design and the pathological identify of steel, reinforced or prestressed concrete and wood structures and also will establish concepts that will be applied to the choice of a corrective method. Apart from this theoretical base, it was presented, "in loco", the pathological demonstration of nine bridges in the region of Campinas (SP), and proposed suggestions about the treatment and correction in each case. To collaborate with these suggestions, two pattern projects of bridges, which were of concrete and steel composite structure and of wood, were developed and annexed to this research. Finally, through this research it is noticed that there is a need of a rigorous mapping of the urban and rural bridges to elevate their useful life and to guarantee the right security to the society. / Mestrado / Estruturas / Mestre em Engenharia Civil

Civil infrastructure throughout the world serves as main arteries for commerce and transportation, commonly forming the backbone of many societies. Bridges have been and remain a crucial part of the success of these civil networks. However, the crucial elements have been built over centuries and have been subject to generations of use. Many current bridges have outlived their intended service life or have been retrofitted to carry additional loads over their original design. A large number of these historic bridges are still in everyday use and their condition needs to be monitored for public safety. Transportation infrastructure authorities have implemented various inspection and management programs throughout the world, mainly visual inspections. However, careful visual inspections can provide valuable information but it has limitations in that it provides no actual stress-strain information to determine structural soundness. Structural Health Monitoring (SHM) has been a growing area of research as officials need to asses and triage the aging infrastructure with methods that provide measurable response information to determine the health of the structure. A rapid improvement in technology has allowed researchers to start using new sensors and algorithms to understand the structural parameters of tested structures due to known and unknown loading scenarios. One of the most promising methods involves the use of wireless sensor nodes to measure structural responses to loads in real time. The structural responses can be processed to help understand the modal parameters, determine the health of the structure, and potentially identify damage. For example, modal parameters of structures are typically used when designing the lateral system of a structure. A better understanding of these parameters can lead to better and more efficient designs. Usually engineers rely on a finite element analysis to identify these parameters. By observing the actual parameters displayed during field testing, the theoretical FE models can be validated for accuracy. This paper will present the field testing of a historic wrought iron truss bridge, in a case study, to establish a repeatable procedure to be used as reference for the testing of other similar structures.

<p dir="ltr">Girder ends of steel bridges can be corrosion damaged due to deicing salts, water, and other contaminants leaking from deck expansion joints. When the corrosion becomes significant, it can decrease the sectional properties of end steel girders and eventually reduce structural resistance against bearing and shear. Conventional methods that are typically used to repair corrosion-damaged girders require a substantial amount of time and resources to complete and often cause public inconvenience due to traffic lane closure. Therefore, there is a need for practical, rapid, and robust repair methods that can be implemented by maintenance personnel of a local Department of Transportation (DOT).</p><p dir="ltr">In this study, five innovative repair methods for corroded steel girders were evaluated through a selection process called the House of Quality Matrix, a commonly used tool in the consumer product industry. After completing the evaluation and additional numerical simulations, the "Sandwich Panel" repair method was selected for further investigation. The main concept of the proposed "Sandwich Panel" repair method is the encasement of the corroded region with a filler material reinforced by threaded rods. Two thin steel plates installed on both girder sides serve as stay-in-place formwork, expediting the installation process. This repair method eliminates labor-intensive steps of jacking, welding, and formwork disassembly, making it more cost-effective and less time-consuming.</p><p dir="ltr">The structural performance of the method was evaluated experimentally by conducting seven large-scale tests. Various test parameters were considered in the tests, including i) threaded rod layout, ii) filler material, and iii) support condition. The test specimens were corrosion-damaged steel girders from decommissioned highway bridges in Indiana. The experimental results indicate that the method is effective enough to recover the girder's original design strength. The experimental evaluation was followed by a numerical parametric study using finite element models benchmarked using the experimental results. Detailed design guidelines and recommendations were developed based on the experimental and numerical results.</p>

A number of older bridges built before the 1970’s were constructed with floor systems consisting of a non-composite concrete slab over steel girders. Many of these bridges do not satisfy current load requirements and may require replacement or strengthening. A potentially economical means of strengthening these floor systems is to connect the existing concrete slab and steel girders to permit the development of composite action. This dissertation describes a research program investigating methods to develop composite action in existing non-composite floor systems by the use of postinstalled shear connectors. Three types of post-installed shear connection methods were investigated. These methods are referred to as the double-nut bolt, the high tension friction grip bolt, and the adhesive anchor. These post-installed shear connectors were tested under static and fatigue loading, and design equations for ultimate strength and fatigue strength were developed. These post-installed shear connectors showed significantly higher fatigue strength than conventional welded shear studs widely used for new construction. The superior fatigue strength of these post-installed shear connectors enables strengthening of existing bridge girders using partial composite design, thereby requiring significantly fewer shear connectors than possible with conventional welded shear studs. Five full-scale non-composite beams were constructed and four of these were retrofitted with post-installed shear connectors and tested under static load. The retrofitted composite beams were designed as partially composite with a 30-percent shear connection ratio. A non-composite beam was also tested as a baseline specimen. Test results of the full-scale composite beams showed that the strength and stiffness of existing non-composite bridge girders can be increased significantly. Further, excellent ductility of the strengthened partially composite girders was achieved by placing the postinstalled shear connectors near zero moment regions to reduce slip at the steel-concrete interface. Parametric studies using the finite element program ABAQUS were also conducted to investigate the effects of beam depth, span length, and shear connection ratio on the system behavior of strengthened partially composite beams. The studies showed that current simplified design approaches commonly used for partially composite beams in buildings provide good predictions of the strength and stiffness of partially composite bridge girders constructed using post-installed shear connectors. / text

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / Pontes de aÃo normalmente estÃo sujeitas a carregamentos cÃclicos de amplitude variÃvel, com tipo e freqÃÃncia de trÃfego ao acaso. Dessa forma, a nucleaÃÃo e a propagaÃÃo de trincas nos elementos estruturais de uma ponte podem ser resultantes das flutuaÃÃes de carregamentos. ApÃs determinar a localizaÃÃo e o tamanho de uma falha existente, tem-se de imediato a preocupaÃÃo com a previsÃo de sua propagaÃÃo a fim de se ter um tempo conveniente para o reparo. Desta maneira, os conceitos de mecÃnica da fratura e fadiga sÃo fundamentais para o correto entendimento do problema. Neste trabalho à feito o desenvolvimento de um modelo computacional para a anÃlise do crescimento de trincas utilizando-se os modelos do Valor MÃdio QuadrÃtico e Ciclo-a-Ciclo. Nas simulaÃÃes realizadas, observa-se a influÃncia dos carregamentos de amplitudes variÃveis sobre a previsÃo de vida da estrutura. Foram consideradas como variÃveis de entrada do programa, diferentes tamanhos iniciais de trincas e diferentes histÃrias de carregamentos. Dessa forma, pÃde-se avaliar a dispersÃo dos resultados de previsÃo de vida da estrutura, com a variaÃÃo dos diferentes parÃmetros de entrada. / Steel bridges are usually subject to variable amplitude cyclic loading, with type and frequency of traffic at random. Thus, the nucleation and propagation of cracks in structural elements of a bridge may be due to fluctuations in shipments. After determining the location and size of a fault existing, has the immediate concern to the prediction of its propagation in order to have a convenient time for repair. Thus, the concepts of fracture mechanics and fatigue are essential for a proper understanding of the problem. This work is done by developing a computational model for the analysis of crack growth models using the mean square value and Cycle-by-cycle. In the simulations, we observe the influence of variable amplitude loading on the expected life of the structure. Were considered as input variables of the program, different initial crack sizes and different loading histories. Thus, we could evaluate the dispersion of expected life of the structure with the variation of different input parameters.

An increase in the demand for the freight shipping in the United States has been predicted for the near future and Longer Combination Vehicles (LCVs), which can carry more loads in each trip, seem like a good solution for the problem. Currently, utilizing LCVs is not permitted in most states of the US and little research has been conducted on the effects of these heavy vehicles on the roads and bridges. In this research, efforts are made to study these effects by comparing the dynamic and fatigue effects of LCVs with more common trucks. Ten Steel and prestressed concrete bridges with span lengths ranging from 30’ to 140’ are designed and modeled using the grid system in MATLAB. Additionally, three more real bridges including two single span simply supported steel bridges and a three span continuous steel bridge are modeled using the same MATLAB code. The equations of motion of three LCVs as well as eight other trucks are derived and these vehicles are subjected to different road surface conditions and bumps on the roads and the designed and real bridges. By forming the bridge equations of motion using the mass, stiffness and damping matrices and considering the interaction between the truck and the bridge, the differential equations are solved using the ODE solver in MATLAB and the results of the forces in tires as well as the deflections and moments in the bridge members are obtained. The results of this study show that for most of the bridges, LCVs result in the smallest values of Dynamic Amplification Factor (DAF) whereas the Single Unit Trucks cause the highest values of DAF when traveling on the bridges. Also in most cases, the values of DAF are observed to be smaller than the 33% threshold suggested by the design code. Additionally, fatigue analysis of the bridges in this study confirms that by replacing the current truck traffic with higher capacity LCVs, in most cases, the remaining fatigue life of the bridge is only slightly decreased which means that taking advantage of these larger vehicles can be a viable option for decision makers.