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The influence of the recommended LRFD Guidelines for the seismic design of highway bridges in Virginia was investigated by analyzing two existing bridges. The first bridge has prestressed concrete girders and is located in the Richmond area. The second bridge has steel girders and is located in the Bristol area. The analysis procedure for both bridges is similar. First the material and section properties were calculated. Then the bridge was modeled in RISA 3D. Live and dead load were imposed on the bridge to calculate the cracked section properties of the bridge. The period of vibration of the bridge was also calculated. After the soil class of the bridge was determined, the design response spectrum curve of the bridge was drawn. The spectral acceleration obtained from the design spectrum curve was used to calculate the equivalent earthquake loads, which were applied to the superstructure of the bridge to obtain the earthquake load effects. Live and dead loads were also applied to get the live and dead load effects. The combined effects of the dead, live and earthquake loads were compared to the interaction diagram of the columns and moment strength of the columns. The details of the bridge design were also checked with the corresponding seismic design requirement.A parametric study was performed to explore the effects of different column heights and superstructure heights in different parts of Virginia. The column longitudinal reinforcing was increased to satisfy the bridge axial loads and moments that are not within the column interaction diagram. / Master of Science

There are many issues and challenges to deal with when designing a curved I-girder bridge. These challenges primarily deal with the many performance stages that curved I-girder bridges have such as the erection, construction, and in-service stages. When design engineers assess the stability of a bridge system, they typically evaluate the system in its final configuration with all cross frames attached and the hardened concrete deck placed. The evaluation of girder stability during erection and early stages of construction stages is difficult because of the limited presence of bracing in the system. Due to a lack of readily available analytical tools, many contractors do not conduct detailed analytical evaluations of the bridge behavior during early stages of the construction when stability is often critical. Instead, many contractors use rules of thumb and experience to ensure stability during erection. Erection and construction practices typically vary among contractors and consistent erection methods are a rarity. Although some rules of thumb may be quite conservative, others are much less so. Therefore, coming up with design guidelines based on parametric studies rather than rules of thumb are desirable to help allow the contractor and the designer to work together to prevent issues that may occur due to the lack of communication between the two professions. Lastly, many challenges arise due to the complex geometry of curved I-girders. To prevent excessive rotation in erected girders, three points of vertical support are often provided. Two of these points usually consist of permanent supports in the form of bridge piers or abutments. The third point of support may consist of a temporary support in the form of a shore tower or holding crane. Cases where a holding crane may be satisfactory over a shore tower are also not well understood. To improve the understanding of lifting practices and temporary support requirements, parametric studies were conducted using the finite element program ANSYS. Field data consisting of displacement, stress, and girder rotations gathered from two tests were used to validate both the linear and geometric non-linear three-dimensional FEA models. Upon validation, the finite element model was used to conduct linear and geometric non-linear analyses to determine critical factors in curved I-girder bridges during construction. Specifically, serviceability limit states were studied for the lifting of curved girders. For partially constructed states, parametric studies were conducted to determine optimal locations to place temporary supports as well as to investigate stability differences between using a shore tower and a holding crane. Recommendations are presented to provide guidance for the lifting of curved I-girders as well as to maximize stability of partially constructed bridges. / text

Concrete highway bridges are important elements of our country's transportation infrastructure; however, only few studies that address their seismic behavior using data collected from instrumented structures are available in the literature. This gap of knowledge impairs full exploitation of structural health monitoring techniques for seismic damage assessment, and improvement of design recommendations. This research is particularly concerned with curved concrete box-girder highway bridges, whose seismic behavior is still widely unexplored due to lack of field monitoring data. By taking advantage of vibration records collected during six earthquake events at the West Street on Ramp, a curved concrete box-girder highway bridge located in Anaheim, California, this research aims at advancing knowledge about the seismic behavior of these bridges. Modal identification of the bridge during the earthquakes is conducted, and sensitivity analysis is carried out to reconcile the observed dynamic characteristics of the bridge with the behavior of its structural elements. Data collected from an instrumented large-scale bridge specimen during shaking table tests are also analyzed to gain insight about the response of the bridge bents during the earthquakes, and propose a strategy to model their seismic behavior. Information from modal identification and the shaking table tests analyses are instrumental in developing a nonlinear finite element model of the bridge, calibrated employing a multistage finite element model updating strategy. In order to evaluate the significance of using the structural-health-monitoring-informed structural model obtained, seismic performance assessment through incremental dynamic analysis is conducted, and results are compared with the predicted performance estimated with a conventional finite element model of the bridge. By advancing knowledge about the seismic behavior of concrete highway bridges, this research may ultimately contribute to improve structural health monitoring practices and design guidelines for this type of structures.

Abstract : Fragility curves are a very useful tool for seismic risk assessment of bridges. A fragility curve describes the probability of a structure being damaged beyond a specific damage state for different levels of ground shaking. Since more than half of all bridges in the province of Quebec (Canada) are in service for more than 30 years and that these bridges were designed at that time without seismic provisions, generating fragility curves for these structures is more than necessary. These curves can be used to estimate damage and economic loss due to an earthquake and prioritize repairs or seismic rehabilitations of bridges. Previous studies have shown that seismic damage experienced by bridges is not only a function of the epicentral distance and the severity of an earthquake but also of the structural characteristics of the bridge and the soil type on which it is built. Current methods for generating fragility curves for bridges do not account for soil conditions. In this work, analytical fragility curves are generated for multi-span continuous concrete girder bridges, which account for 21% of all bridges in Quebec, for the different soil profile types specified in the Canadian highway bridge design code (CAN/CSA-S6-06). These curves take into account the different types of abutment and foundation specific to these bridges. The fragility curves are obtained from time-history nonlinear analyses using 120 synthetic accelerograms generated for eastern Canadian regions, and from a Monte Carlo simulation to combine the fragility curves of the different structural components of a bridge||Résumé : Les courbes de fragilité sont un outil très utile pour l’évaluation du risque sismique des ponts. Une courbe de fragilité représente la probabilité qu'une structure soit endommagée au-delà d'un état d'endommagement donné pour différents niveaux de tremblement de terre. Étant donné que plus de la moitié des ponts dans la province de Québec (Canada) ont plus de 30 années de service et que ces ponts n'ont pas été conçus à l'époque à l'aide de normes sismiques, la génération de courbes de fragilité pour ces structures est plus que nécessaire. Ces courbes peuvent servir à estimer les dommages et les pertes économiques causés par un tremblement de terre et à prioriser les réparations ou les réhabilitations sismiques des ponts. Des études antérieures ont montré que l'endommagement subi par les ponts suite à un tremblement de terre n'est pas seulement fonction de la distance de l'épicentre et de la sévérité du tremblement de terre, mais aussi des caractéristiques structurales du pont et du type de sol sur lequel il est construit. Les méthodes actuelles pour générer les courbes de fragilité des ponts ne tiennent pas compte des conditions du sol. Dans ce travail de recherche, des courbes de fragilité analytiques sont générées pour les ponts à portées multiples à poutres continues en béton armé, soit pour 21% des ponts au Québec, pour les différents types de sol spécifiés dans le Code canadien sur le calcul des ponts routiers (CAN/CSA-S6-06). Ces courbes prennent en compte les différents types de culée et de fondation spécifiques à ces ponts. Les courbes de fragilité sont obtenues à partir d'analyses temporelles non linéaires réalisées à l'aide de 120 accélérogrammes synthétiques généres pour l’est du Canada, et d'une simulation de Monte Carlo pour combiner les courbes de fragilité des différentes composantes du pont.

This thesis examines the development of a superstructure for a slab-on-girder wood-concrete composite highway bridge. Wood-concrete composite bridges have existed since the 1930's. Historically, they have been limited to spans of less than 10 m. Renewed research interest over the past two decades has shown great potential for longer span capabilities. Through composite action and suitable detailing, improvements in strength, stiffness, and durability can be achieved versus conventional wood bridges. The bridge makes use of a slender ultra-high performance fibre-reinforced concrete (UHPFRC) deck made partially-composite in longitudinal bending with glued-laminated wood girders. Longitudinal external unbonded post-tensioning is utilized to increase span capabilities. Prefabrication using double-T modules minimizes the need for cast-in-place concrete on-site. Durability is realized through the highly impermeable deck slab that protects the girders from moisture. Results show that the system can span up to 30 m while achieving span-to-depth ratios equivalent or better than competing slab-on-girder bridges.

This thesis examines the development of a superstructure for a slab-on-girder wood-concrete composite highway bridge. Wood-concrete composite bridges have existed since the 1930's. Historically, they have been limited to spans of less than 10 m. Renewed research interest over the past two decades has shown great potential for longer span capabilities. Through composite action and suitable detailing, improvements in strength, stiffness, and durability can be achieved versus conventional wood bridges. The bridge makes use of a slender ultra-high performance fibre-reinforced concrete (UHPFRC) deck made partially-composite in longitudinal bending with glued-laminated wood girders. Longitudinal external unbonded post-tensioning is utilized to increase span capabilities. Prefabrication using double-T modules minimizes the need for cast-in-place concrete on-site. Durability is realized through the highly impermeable deck slab that protects the girders from moisture. Results show that the system can span up to 30 m while achieving span-to-depth ratios equivalent or better than competing slab-on-girder bridges.