The torsional rigidity of tub-girder makes them ideal for use in curved bridges. The use on skewed support applications by bridge designers is limited as the behavior is complex and requires the use of advanced analysis tools. In consequence, a simplified analysis method to account for the effects of skew on tub-girder twist rotations and internal torques and how these affect the internal component forces was proposed. The combined effects of skew and curvature are studied by examining the results for analysis with different levels of sophistication for 18 representative bridges. The data generated constitutes the first systematic study on a large set of curved and skewed tub-girder bridges using consistent, refined 3D FEA models to model construction forces and deformations. Comparisons of the simplified analysis method to the refined 3D FEA analysis display the limitations of the simplified analysis and present potential sources of error. Furthermore, the results from the 3D FEA helped identify interactions between components and, therefore, an improved simplified procedure was proposed to account for the effects of the resulting increased stresses. In addition, the bridge erection procedures are discussed and specific examples illustrating the calculation of the fit-up forces is presented. These findings provided additional tools for the analysis process and erection engineering to account for the effects of skew. Lastly, further research needs considering the analysis of additional loading conditions and construction procedures are described.

<p>Research in the area of bridge design has been and still isconcentrated on the study of the strength of materials andrelatively few studies have been performed on traffic loads andtheir effects. Traffic loads have usually been assumed to begiven in codes. This is mainly because it is very difficult tomodel traffic loads in an accurate manner because of theirrandomness.</p><p>In this work, statistical evaluations of traffic loadeffects, obtained from real as well as Monte Carlo (MC)simulated vehicle data, are presented. As the dynamiccontribution of the vehicle load was filtered by the systemused for measuring vehicle weight, no attention was paid in thepresent study to the dynamic effects or the impact factor. Thedynamic contribution of the traffic load models from codes wasdeducted wherever they were compared with the result from theevaluation of the real data. First, the accuracy of thecollected data was investigated. This was done to examine theinfluence of what was most probably unreasonable data on thefinal evaluated results. Subsequently, the MC simulationtechnique, using a limited amount of the collected data, wasused to generate fictitious vehicle data that could representresults from field measurements which would otherwise have tobe recorded under a long period. Afterwards, the characteristictotal traffic loads for bridges with large spans weredetermined by probabilistic analysis. This was done using realas well as simulated data and the two were compared. Theseresults were also compared with the corresponding valuescalculated using the traffic load model from the Swedish bridgedesign code.</p><p>Furthermore, using traffic data, different load effects onbridges (girder distribution factor of slab-on-girder bridgesand the mid-span deflection as well as the longitudinal stressat critical locations on box-girder bridges) were investigated.The main task was to obtain a more accurate knowledge oftraffic load distributions on bridges as well as their effectsfor infrastructure design. The results showed that the trafficload models from codes gave considerably higher load effectscompared to the current actual traffic load effects. Theseinvestigations were based on the available data for the actualposition of the vehicles on a single bridge and might not coverall possible traffic scenarios. The results showed only how thereal traffic loads, under”normal”conditions andtheir transverse positions relate to the load model accordingto the codes.</p><p><b>KEYWORDS:</b>bridge, traffic load, load effect, transversedistribution, characteristic value,weigh in motion, MonteCarlo simulation, Rice’s formula, level crossinghistogram, vehicle queue.</p>

<p>Before 1992 the Swedish Road Administration (SRA) carried out all bridge maintenance and minor repair for all bridges in Sweden by themselves. The bridge maintenance crew in a county consisted typically of 3-6 workers and a bridge-engineer.</p><p>SRA and some contractors suggest that it could be a good idea for SRA to procure bridge maintenance in one or two counties for a long-time, e. g., seven to ten years. The bridge maintenance crew could be a model for this.</p><p>The aim of the research project is to present an updated model for procurement of bridge maintenance based on functional requirements. The base for this updated model will be the findings and conclusions that could be drawn from a real project – a case study. The research project shall continuously follow-up the performed maintenance and document how the contractor is planning and performing the work. The research will specially focus on measurable verifying methods for the performed maintenance. The results from the research project will be evaluated and compared with standard maintenance methods and the results will hopefully be used to update current regulations. The hope is also that the contractor will develop new and effective maintenance methods with the larger freedom a functional contract enables. At the end the final goal is to reduce the cost for the society for bridge maintenance in the future.</p><p>The basic idea behind performance contract is that the client makes measurable functional demands with regard to the finished product, instead of presenting technical solutions. As an example the client could demand a certain friction and smoothness for the road surface. These functional demands should be formulated so that they have a direct relevance for the safety and flow of traffic.</p><p>It is important that these functional requirements are divided into a target level and an absolutely lowest possible level (acute level). A contractor should maintain the target level both as an average functional level during the contract period and when the contract is completed. For the acute level there should be stipulated a maximum allowable time before corrective action needs to be taken.</p><p>The methods that have been used in the research project are interviews, meetings, literature studies, reports, follow-up, statistics, participating in seminars, the authors own inspections, annual reports and so on.</p><p>Since the author didn’t find anything published about bridge management on performance contract, to the author’s best knowledge, the literature studies have been concentrated on nearby topics, e. g., highways on performance contract and bridge maintenance in general et cetera.</p><p>The research project has so far consisted mostly of a pilot study. From the beginning the idea behind the project was:</p><p>• To procure bridge maintenance for the small and mid-sized bridges,</p><p>• in one or two counties,</p><p>• for a longer time, e. g., seven to ten years.</p><p>• The value of a maintenance contract could be in the range of about 100 MSEK for the whole time.</p><p>Since this is the first project of its kind in Sweden the owner (SRA) did not dare to let this pilot project be too voluminous. What will be tested and followed by this research project is to use contracting for maintenance based on functional requirements for all 400 bridges in Uppsala County in Sweden and for a period of three years and with an option for three more years. Uppsala County is situated some 20 km to 200 km north of Stockholm.</p><p>To summarise the actual contract:</p><p>• A contractor should perform bridge maintenance for all 400 bridges in Uppsala County.</p><p>• The contract was three years (1 Sept. 2004 – 31 Aug. 2007) with an option for three more years (1 Sept. 2007 – 31 Aug. 2010).</p><p>• The bridges were deemed to be in satisfactory condition if the contractor verified that they met the functional requirements in SRA’s regulations once a year.</p><p>• Repair of 25 bridges during the contract’s first three years.</p><p>• If the option for three more years will be used, then there will be some additional bridge repairs.</p><p>• The contractor was expected to contribute in the research project.</p><p>There were six contractors that requested the tender documents, but only three of them submitted an offer to SRA, see table below.</p><p>Contractor Submitted offer</p><p>Vägverket Produktion 20 387 943 SEK</p><p>DAB-Domiflex AB 23 728 040 SEK</p><p>NCC Construction 28 620 000 SEK (Advance 2 000 000 SEK)</p><p>All of the three contractors deemed to have met the standards of a contractor set by SRA. Vägverket Produktion (VP) was the lowest bidder and therefore it was contracted by SRA for this project.</p><p>Interviews were carried out with all six contractors that had requested tender documents. All of them thought that a multiyear bridge maintenance contract was an interesting idea. Large companies tend to want large contracts and small companies tend to settle for smaller contracts. All of the contractors thought that it was easy to calculate the 25 bridge repairs compared to bridge maintenance on functional demands.</p><p>According to the contract VP should repair 25 bridges during a three year period. VP divided these repairs in three equal parts: nine bridges 2005, eight bridges 2006 and eight bridges 2007.</p><p>The functional requirements for the bridges should be verified once a year according to the contract. Both representatives for SRA and VP carried out bridge inspections during the first year and it was noted that the representatives had a different view on some of the discovered defects on the bridges. The representatives had a different view mainly on the bridges’ structural members’ slope and embankment end, edge beam and surfacing. It is important to specify how to measure and interpret the results from inspections regarding defects in functional requirements. Defects in functional requirements should be divided into acute defects and non-acute defects. Acute defects needs to be more precisely defined but could be surfacing against bridge, settling in slope and embankment end and flushing.</p><p>These defects should be rectified as soon as possible. Non-acute defects could be rectified when there is enough work for the contractor to carry out but not later then October 31st every year. The research project will continue to follow-up and evaluate the first three years of the pilot study.</p><p>The research project will also follow-up and evaluate if the option for extending the contract three more years will be used. According to the contract, if the option will be used, there need to be a meeting between the client and the contractor not later than 31 Aug. 2006 and a settlement need to be reached not later than 30 Sep. 2006.</p><p>It is of interest to study the possibility to use, in future tender documents, the indicator Lack of Capital Value and/or the average permissible level of defects in functional requirements for the bridge stock. Further research should also be focused on how defects on different members of the bridge evolve and the cost associated to rectify them. It is of interest to know how many defects that are evolved during a normal year for the 400 bridges in the study. If one knew the number of defects one can estimate the costs to rectify these. The estimated cost can then be included as information for the potential contractor in future tender documents.</p><p>So far SRA’s representatives are satisfied with the project and with the good relationship that evolved between SRA and the contractor. SRA is also satisfied with the increased focus on the bridge functional requirements.</p><p>If this project will continue to show good results then SRA will consider procure bridge maintenance on similar contracts for more counties.</p>

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 166-174).

Thesis (Masters) -- Simmons College, 2009. / Includes bibliographical references (l. 64-66)

The concept of bridge blogs and their function to foster awareness and public discourse across the world was examined by content analysis and network analysis of 426 blog posts and 1026 links in 11 bridge blogs about China from 2009 to 2010. This study proposes a theoretical framework to examine how bridge blogs’ network characteristics are related to their communicative practices. Three variables were examined with respect to the network characteristics of bridge blogs. First, this study identifies different types of bridge blogs according to the distinctive sites with which they choose to link. Second, bridge blogs’ role as bridges is directly tested by the extent to which they connect between online information sources that are otherwise separated from one another. Third, this study examines bridge blogs’ level of centrality, which is based on the number links they receive from others in the network. For communicative practices, this study measures the type of links bridge blogs use as sources in their posts and the communicative frames used to structure the blog posts. Bridge blogs exhibit internal diversity in terms of what distinctive sites they linked to, level of betweenness and centrality. The finding supports the theoretical framework proposed in the study that bridge blogs’ three network characteristics are associated with their practices of communication as reflected in their use of links and content structure. Bridge blogs that play a crucial interconnecting role and are central points of reference in the network are more likely to bring Chinese content (as oppose to Western media coverage) and citizen voice (as oppose to professional media content) to English speaking readers. In addition, the translation of Chinese content, which contributes more to the flow of information and views from China to the outside world, is valued more by bridge blogs (than others?) that are important interconnecting actors in the network and positioned as central points of attention in the network. Further, a textual analysis further enriches the understanding of how the communicative frames are practiced by the bridge blogs, as illustrated in their references to four high profile news stories about China. / text

Corrosion of embedded reinforcement is the leading form of deterioration affecting the integrity of reinforced and prestressed concrete bridge members around the world. If undetected, corrosion can limit the service life of the bridge and lead to expensive repairs. The research team at the University of Texas at Austin has developed a new class of passive wireless corrosion sensors. The noncontact (NC) sensor platform provides an economical and nondestructive means for detecting corrosion initiation within concrete. The sensor is powered through the inductive coupling to an external mobile reader that can be handheld or mounted on a vehicle. It is envisioned that the four-dollar sensor will be embedded in concrete during construction and interrogated sporadically over the service life of the structure. The sensor output can be used to detect corrosion initiation within concrete and is expected to enhance the quality information collected during qualitative routine bridge inspections. The NC sensor prototype consists of a resonant circuit that is inductively coupled to a sacrificial transducer. Corrosion of the sacrificial element alters the measured sensor response and is used to detect corrosion within concrete. Electrochemical evaluations were conducted to ensure that the sacrificial element exhibited identical response as the reinforcement steel. In addition, the results of extensive experimental parametric studies were used in conjunction with circuit and electromagnetic finite element models to optimize the NC sensor design. Long-term exposure tests were used to evaluate the reliability of the passive noncontact sensors. Sensors were embedded in reinforced concrete specimens and successfully detected the onset of corrosion in the adjacent reinforcement. Unlike the traditional corrosion evaluation methods, such as half-cell potentials, the sensors output was insensitive to environmental variations. / text

Prestressed concrete construction relies on the application of compressive stresses to concrete elements. The prestressing force is typically applied through the tensioning of strands that react against the concrete and induce compression in the concrete. Loss of prestress is the decrease of this pre-applied stress. The conservative estimation of the prestress losses is imperative to prevent undesired cracking of the prestressed element under service loads. A large fraction of the prestress losses is a consequence of concrete deformations. This fraction of the losses can be identified as strain-related losses, and these occur due to instantaneous elastic shortening, and time-dependent creep and shrinkage. Creep and shrinkage of concrete depend on many factors that are extremely variable within concrete structures. The time-dependent behavior of concrete is not well-understood, but recent findings in the topics of concrete creep and shrinkage provide a better understanding of the underlying mechanisms affecting the nature of these two phenomena. However, current design practices and prestress loss estimation methods do not reflect the state-of-the-art knowledge regarding creep and shrinkage. The main objective of this dissertation was the study and estimation of strain-related prestress losses in simply supported pretensioned bridge girders. Simply supported pretensioned girders are widely designed, produced and frequently used in bridge construction. Due to this common use, pretensioned concrete bridge girders has become fairly standardized elements, which results in a reduced variability in the behavior of pretensioned bridge girders, as compare to that of less standardized concrete structures. Hence, a simplified method was calibrated to estimate prestress losses within pretensioned girders to an adequate level of accuracy. To achieve an acceptable accuracy experimental data from the monitoring of pretensioned simply supported girders was used for the calibration of the method. The accuracy of this simplified method is comparable to that achievable using more elaborate methods developed for generic concrete structures. / text

Identifying damage of a bridge from a vehicle moving over it is an attractive idea especially for those bridges without structural health monitoring systems as it is faster than putting sensors on the bridges. Many parts of highways and railways have been constructed on bridges and it is important to ensure that they are in good conditions. Therefore a large amount of bridges need to be monitored and for the sake of economy the monitoring should be efficient. If an instrumented vehicle can identify the occurrence and locations of damage by running over the bridges, it would save a lot of labor and time. As acceleration is easier to acquire, it is used as the main signal for damage detection. Research in this area is relatively little, not to mention the need to take into account road surface roughness and experimental verification. Frequencies can be conveniently extracted from the vehicle response. The damage can hence be identified based on the relationship between the change of frequencies and the fractional change of strain energy. A vehicle-bridge interaction system is used to simulate the process of a vehicle running over a bridge and obtain the vehicle response for investigation. The proposed method can identify damage of simply supported and multi-span continuous bridges taking into account road surface roughness and measurement noise. They are also validated in the laboratory where a simply supported bridge is modeled using an aluminum beam and the vehicle is modeled with aluminum vehicles. This method can limit the damage location to two potential locations. The multi-level multi-pass strategy makes use of the identification from the above method, applies genetic algorithm and lets the vehicle run over the bridge at various speeds. The unique damage location can then be identified. A numerical study for simply supported bridges and multi-span continuous bridges has verified its effectiveness. Continuous wavelet transform (CWT) can identify local changes in a signal as damage is assumed to cause local change to the vehicle response, which makes it suitable for damage detection from vehicle response. However, the road surface roughness and measurement noise often mask the information about damage. Smoothing technique and damage indicators are proposed to help with the identification. By validating the method with a numerical vehicle-bridge interaction system and model tests in the laboratory, the damage can be correctly identified. Additional masses and sinusoidal excitation force can help with the identification too. Repeated application of CWT involves applying the CWT to the coefficients of continuous wavelet again and again, which can also improve the results. If CWT is treated as a mathematical microscope, repeated application of CWT is like amplifying the signal several times. The effectiveness of the method has been verified numerically and experimentally. In summary, a convenient and efficient technique to test the conditions of bridges by putting sensors on a moving vehicle is proposed and the method is verified by numerical and experimental studies. It can provide an alternative or a useful complement to conventional structural health monitoring systems. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

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