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.

The construction of horizontally curved bridges with skewed supports requires careful consideration. These types of bridges exhibit three-dimensional response characteristics that are not commonly seen in straight bridges with normal supports. As a result, engineers may face difficulties during the construction, when the components of the bridge do not fit together or the final geometry of the structure does not correspond to that intended by the designer. These complications can lead to problems that compromise the serviceability aspects of the bridge and in some cases, its structural integrity. The three dimensional response that curved and skewed bridges exhibit is directly influenced by the bracing system used to configure the structure. In I-girder bridges, cross-frames are provided to integrate the structure, transforming the individual girders into a structural system that can support larger loads than when the girders work separately. In general, they facilitate the construction of the structure. However, they can also induce undesired collateral effects that can be a detriment to the performance of the system. These effects must be considered in the design of a curved and skewed bridge because, in some cases, they can modify substantially its response. This research is focused on understanding how the bracing system affects the performance of curved and skewed I-girder bridges, as well as, the ability of the approximate analysis methods to capture the structural behavior. In this research, techniques that can be implemented in the creation of 2D-grid models are developed to overcome the limitations of this analysis method. In addition, efficient cross-frame arrangements that mitigate the collateral effects of skew are developed. These mitigation schemes reduce the undesired cross-frame forces and flange lateral bending stresses associated with the transverse stiffness of the structure, while ensuring that the bracing system still performs its intended functions.

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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.

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

Curved and skewed I-girder bridges exhibit torsional displacements of the individual girders and of the overall bridge cross-section under dead loads. As a result, the girder webs can be plumb in only one configuration. If the structure is built such that the webs are plumb in the ideal no-load position, they generally cannot be plumb under the action of the structure's steel or total dead load; hence, twisting of the girders is unavoidable under dead loads. The deflected geometry resulting from these torsional displacements can impact the fit-up of the members, the erection requirements (crane positions and capacities, the number of temporary supports, tie down requirements, etc.), the bearing cost and type, and the overall strength of the structure. Furthermore, significant layover may be visually objectionable, particularly at piers and abutments. If the torsional deflections are large enough, then the cross-frames are typically detailed to compensate for them, either partially or fully. As specified in Article C6.7.2 of the AASHTO LRFD Specifications, different types of cross-frame detailing methods are used to achieve theoretically plumb webs under the no-load, steel dead load, or total dead load conditions. Each of the cross-frame detailing methods has ramifications on the behavior and constructability of a bridge. Currently, there is much confusion and divergence of opinion in the bridge industry regarding the stage at which steel I girder webs should be ideally plumb and the consequences of out-of-plumbness at other stages. Furthermore, concerns are often raised about potential fit-up problems during steel erection as well as the control of the final deck geometry (e.g., cross-slopes and joint alignment). These influences and ramifications of cross-frame detailing need to be investigated and explained so that resulting field problems leading to needless construction delays and legal claims can be avoided. This dissertation addresses the influence of cross-frame detailing on curved and/or skewed steel I girder bridges during steel erection and concrete deck placement by conducting comprehensive analytical studies. Procedures to determine the lack-of-fit forces due to dead load fit (DLF) detailing are developed to assess the impact of different types of cross-frame detailing. The studies include benchmarking of refined analytical models against selected full scale experimental tests and field measurements. These analytical models are then utilized to study a variety of practical combinations and permutations of bridge parameters pertaining to horizontal curvature and skew effects. This research develops and clarifies procedures and provides new knowledge with respect to the impact of cross-frame detailing methods on: 1) constructed bridge geometries, 2) cross-frame forces, 3) girder stresses, 4) system strengths, 5) potential uplift at bearings, and 6) fit-up during erection. These developments provide the basis for the development of refined guidelines for: 1) practices to alleviate fit-up difficulties during erection, 2) selection of cross-frame detailing methods as a function of I-girder bridge geometry characteristics, and 3) procedures to calculate the locked-in forces due to DLF cross-frame detailing.

This study investigates the complex issues surrounding the preservation of historic, single-lane, metal truss bridges. Essentially functionally obsolete, these structures are targeted for replacement due to current government transportation policies, funding requirements, and safety concerns. After these issues are discussed, a series of case studies from Hunterdon County, New Jersey, will highlight multiple bridge rehabilitation projects in which designs and plans were modified to suit the unique situations and conditions of each of these structures, without compromising historic integrity and improving safety. These bridges have important cultural value, and although in some cases the original structure may be lost or wholly reconstructed, the historic character of the bridge and area is retained. This thesis illuminates the difficulties that need to be overcome in attempting to successfully preserve historic, single-lane bridges and their rural context (while maintaining transportation functionality), and illustrates the important role of community involvement in the preservation process. / Department of Architecture