Suchergebnisse

Optimising the strategy for repairing, upgrading and replacing bridges in the European Union, and elsewhere, is becoming increasingly important due to ageing of the bridge stock, continuously increasing load requirements and budgetary limitations. Thus, there is a clear need to identify or develop, and implement, refined methods for assessing existing bridges in order to determine the most cost-effective options and actions to extend their lives, increase their capacities or replace them.Thus, the objective of the research project partly reported in this licentiate thesis is to verify and calibrate methods for refined assessment of existing bridges, using information acquired in an extensive program of experimental studies. In addition to describing parts of the project, the thesis is intended to provide a basis for suggestions and a discussion of the author's future research in the area. It includes presentations of two experimental studies designed to evaluate, and calibrate, assessment methods:1. A laboratory-based experimental study of 12 two-span continuous reinforced concrete beams conducted in Dublin, Ireland, in 2012. The tests particularly focused on the beams' nonlinear overall behaviour and related redistribution of internal forces.2. A full-scale test of a 55 year-old post-tensioned girder bridge in Kiruna, Sweden, in 2014, focusing on: (a) failure loading of the main girders, (b) failure loading of the slab, (c) the condition of post-tension cables, and (d) two strengthening systems using carbon fibre reinforced polymers (CFRP).The continuous reinforced concrete beams behaved in a nonlinear manner from an early stage in the loading. This is not usually considered in either the design or assessment of existing bridges, but should be for the verification to be accurate at the serviceability and ultimate limit states (SLS and ULS, respectively). The results also indicated that there was more redistribution of internal forces at the ULS than stated in standards. Thus, use of refined methods to assess bridges or other reinforced concrete structures can be beneficial for avoiding unnecessary repairs, strengthening or replacement measures. In addition, the tests demonstrated the importance of taking into account the interaction between flexural moments and shear forces. This is not considered in shear force resistance models included in, for example, the European standard.To date, too few reinforced concrete bridges have been tested to failure to parameterise assessment models robustly with low uncertainty levels. Thus, a programme aimed for verification and calibration of models for assessing existing bridges was designed. The comprehensive programme is described in the thesis, which also provides suggestions and a discussion for future research based on the tests and associated monitoring.During the full-scale tests of the Kiruna Bridge, data were acquired that are relevant to investigations in several fields related to bridge assessment. For instance the obtained data provide foundations for future research concerning: (a) the robustness, ductility and bridge behaviour, (b) the shear force and punching resistance of bridge girders and slabs, (c) assessment of post-tensioned steel cables' condition, (d) strengthening methods using CFRP, (e) updating finite element models, and (f) reliability-based analysis. ; Godkänd; 2014; 20141031 (nikbag); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Niklas Bagge Ämne: Konstruktionsteknik/Structural Engineering Uppsats: Assessment of Concrete Bridges Models and Tests for Refined Capacity Estimates Examinator: Professor Björn Täljsten, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Tekn Dr Anders Carolin, Trafikverket, Luleå Tid: Torsdag den 18 december 2014 kl 10:00 Plats: D770, Luleå tekniska universitet

AbstractThe conventional wisdom about political science international education assumes that students choose between short "island" study abroad programs that are accessible but have only superficial impact, and longer immersion programs, achieving a greater effect. This article argues that well-designed study abroad programs can combine the best of both models to achieve significant impact even in a short program. It proposes a "bridge model" for reconceptualizing study abroad not as a discrete event with more or less impact on student learning, but as a key intervention that furthers a student's overall development within an internationalized curriculum. The article examines the case of a peacebuilding study abroad program in Ecuador. It measures alumni perceptions of impact, objective outcomes, and alumni network development. The key finding is that solid program design and structured cross-cultural interaction produces the type of long-term effect and networks traditionally associated with immersion programs.

ABSTRACTThis paper presents a model to predict French gross domestic product (GDP) quarterly growth rate. The model is designed to be used on a monthly basis by integrating monthly economic information through bridge models, for both supply and demand sides, allowing thus economic interpretations. For each GDP component, bridge equations are specified by using a general‐to‐specific approach implemented in an automated way by Hoover and Perez and improved by Krolzig and Hendry. This approach allows to select explanatory variables among a large data set of hard and soft data. A rolling forecast study is carried out to assess the forecasting performance in the prediction of aggregated GDP, by taking publication lags into account in order to run pseudo real‐time forecasts. It turns out that the model outperforms benchmark models. The results show that changing the set of equations over the quarter is superior to keeping the same equations over time. In addition, GDP growth seems to be more precisely predicted from a supply‐side approach rather than a demand‐side approach.

While the West is struggling to find a way out of recession, emerging markets present myriad opportunities for growth. This paper offers a new perspective on how global economic triangulation facilitates trade between regions. Triangulation occurs where barriers exist to trade and investment between two countries and a third party (e.g., a country) acts as a facilitator or bridge. The "bridge model," as we call it, shifts the focus away from national policy as a facilitator of international trade and emphasizes the role of companies. Corporate bridge-building is essentially a form of economic triangulation, and we use the terms "bridge" and "triangulation" interchangeably. Various examples are cited to show how Spanish multinational companies have served as a bridge connecting Asia and Latin America, and in so doing have expanded their own business. Thanks to their links with both regions they create business relationships that might otherwise be impeded by cultural or language barriers, facilitating the flow of products, knowledge and financial resources. In this way firms in otherwise stagnating economies have an opportunity to grow by facilitating trade and investment between emerging markets via the bridge model.

This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this record ; Bridge Weigh-in-Motion (B-WIM) systems use the bridge response under a traversing vehicle to estimate its axle weights. The information obtained from B-WIM systems has been used for a wide range of applications such as pre-selection for weight enforcement, traffic management/planning and for bridge and pavement design. However, it is less often used for bridge condition assessment purposes which is the main focus of this study. This paper presents a bridge damage detection concept using information provided by B-WIM systems. However, conventional B-WIM systems use strain measurements which are not sensitive to local damage. In this paper the authors present a B-WIM formulation that uses rotation measurements obtained at the bridge supports. There is a linear relationship between support rotation and axle weight and, unlike strain, rotation is sensitive to damage anywhere in the bridge. Initially, the sensitivity of rotation to damage is investigated using a hypothetical simply supported bridge model. Having seen that rotation is damage-sensitive, the influence of bridge damage on weight predictions is analysed. It is shown that if damage occurs, a rotation-based B-WIM system will continuously overestimate the weight of traversing vehicles. Finally, the statistical repeatability of ambient traffic is studied using real traffic data obtained from a Weigh-in-Motion site in the U.S. under the Federal Highway Administration's Long-Term Pavement Performance programme and a damage indicator is proposed as the change in the mean weights of ambient traffic data. To test the robustness of the proposed damage detection methodology numerical analysis are carried out on a simply supported bridge model and results are presented within the scope of this study. ; European Union's Horizon 2020