The theme of the master’s thesis is detailed design bridge structure. The thesis is devoted to limit states assessment of the structure. The thesis includes a time analysis structure and a detailed solution influence of construction on its proposal.

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Prestressed concrete bridges are susceptible to deterioration over time which might significantly affect their capacity and overall performance. In previous decades, infrastructure owners have found that continuous monitoring of these assets is a valuable tool for their management as it facilitates the decision-making process regarding the intervention strategies required. However, as data acquisition and measurement technologies have advanced tremendously in recent years, the amount of information that can be retrieved daily is not easy to manage and analyse. This study presents an evaluation of the effectiveness between different machine learning methods regarding prediction and interpretation of structural responses as well as the feasibility of mapping an independent variable, aspects such as metric performance, learning curves and residual plots was analysed. A comparison was made on the machine learning algorithms performing regression analysis where each model scored over 98% in the R-square metric. This study utilised data collected from a prestressed concrete bridge located in Autio, northern Sweden, that has been continuously monitored for more than three years.

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The Hampton Roads Bridge-Tunnel is one of the oldest prestressed concrete structures in the United States. The 3.5 mile long twin structure includes the world's first underwater tunnel between two man-made islands. Throughout its 60 years in service, the harsh environment along the Virginia coast has taken its toll on the main load carrying girders. Concrete spalling has exposed prestressing strands within the girders allowing corrosion to spread. Some of the more damaged girders have prestressing strands that have completely severed due to the extensive corrosion. The deterioration has caused select girders to fail the necessary load ratings. The structure acts as an evacuation route for the coast and is a main link for the local Norfolk Naval Base and surrounding industry. Because of these constraints, load posting is not a viable option. Live load testing of five spans was performed to investigate the behavior of the damaged spans. Innovative techniques were used during the load test including a wireless system to measure strains. Two different deflection systems were implemented on the spans, which were located about one mile offshore. The deflection data was later compared head to head. From the load test results, live load distribution factors were developed for both damaged and undamaged girders. The data was also used by the local Department of Transportation to validate computer models in an effort to help pass the load rating. Overall, this research was at the forefront of the residual strength of prestressed concrete girders and the testing of in-service bridges. / Master of Science / According to Federal law, each bridge across the United States must be inspected by a licensed engineer on a biennial cycle – meaning every two years. Roughly every ten years, or when major work is performed such as a bridge widening, a load rating must be performed. During a load rating, licensed structural engineers analyze every structural component of a bridge under various loads. These loads include general traffic loads, heavy design loads, as well as special permit truck loads. For each of these loadings, it is proven whether each structural component has enough strength to withstand the load entering the member. Inspection reports are incorporated into the load rating analysis to account for any deterioration in the members which will lower its strength. Recently, a load rating was performed on the Hampton Roads Bridge-Tunnel. The Bridge-Tunnel is a 3.5 mile long twin structure located in Southeastern Virginia. Throughout its 60 years in service, the harsh coastal environment has caused extensive deterioration to some of its main load carrying girders. The deterioration has caused the Bridge-Tunnel to fail its load ratings meaning load posting may have to be imposed. This means signs, and possibly security guards, would have to be implemented before the approach ramps preventing trucks over a certain weight limit from entering. The structure acts as an evacuation route for the coast and is a main link for the local Norfolk Naval Base and surrounding industry. Because of these constraints, load posting is not a viable option. The Bridge-Tunnel is one of the oldest structures of its type so the effects of the deterioration are not well understood causing conservative assumptions to be used within the load rating. This research describes load testing that was performed on the structure to understand the performance and deterioration effects of the bridge. The results and recommendations from this research were used by the load rating engineers to justify assumptions made and help pass the load rating.

The first objective of this thesis was to determine the material properties of grade 270 and grade 300 prestressing strand of various sizes. Tension tests were performed on each type of strand. The data from these tests was used to determine modulus of elasticity, yield stress, ultimate stress, and ultimate elongation for each strand. The yield stresses and ultimate stresses for many of the strands did not meet the requirements found in ASTM A416. The ultimate elongation results far exceeded the requirements and the measured elastic moduli were near the modulus recommended by AASHTO LRFD. A secondary objective from the tension tests was to evaluate a gripping method which used aluminum tubing to cushion the strands against notching. The grips performed very well. Most of the strand breaks did not occur in the grips and when a strand did break in the grips, the failure occurred after significant post-yield elongation. The second objective was to evaluate the bond properties of grade 270 and grade 300 prestressing strands. The North American Strand Producers (NASP) Bond Test and Large Block Pullout Test (LBPT) were performed on six different strand grade and strand size combinations. Both of the tests are simple pullout tests on untensioned strand. The results for each strand type were compared to one another as well as to measured transfer and development lengths from beams using the strand from the same reel. All of the strands showed sufficient bond in the beams, but one strand type did fail both the NASP Test and the LBPT. Both pullout tests were acceptable methods to evaluate strand surface condition and the benchmarks set for 0.5 in. diameter regular strand were conservative for the strands used in this thesis. Little difference was evident in the bond performance of grade 270 and grade 300 prestressing strand. / Master of Science

An experimental program was conducted at the Ferguson Structural Engineering Laboratory of The University of Texas at Austin, under the auspices of Texas Department of Transportation (TxDOT) Research Project 5831, to investigate the tensile stresses that develop in the end regions of pretensioned concrete U-beams at transfer of prestress. Understanding the effect of these “bursting” and “spalling” stresses is essential in order to design standard details that might lead to reliably-serviceable end regions. Two full-scale beam specimens, designed to be worst-case scenarios for bursting and spalling, were fabricated. Each beam had one square and one highly skewed end. Extensive instrumentation, including strain gages on transverse and lateral reinforcing bars, was employed in the end regions of these U-beams. Experimentally determined bursting and spalling stresses in these bars were compared to results of past projects (from the literature) investigating I-beams and inverted T-beams. Preliminary recommendations are made for changes in the standard reinforcing details for U-beam end regions. Such recommended details will be tested in the upcoming phase of Research Project 5831. / text

Šiame darbe nagrinėjama standžių sujungimo mazgų įrengimo įtaka iš anksto įtemptų surenkamų gelžbetoninių sijų laikomajai galiai ir įlinkiams. Laikomosios galios analizės metu nagrinėjama sijų ribinės apkrovos ir tempiamos zonos armatūros kiekio priklausomybė nuo standžiai jungčiai įrengti naudojamos jungiamosios armatūros skerspjūvio ploto ir betono klasės. Sijų įlinkių analizės metu nagrinėjama, kiek galima sumažinti sijų įlinkius, skerspjūvio aukštį ar padidinti tarpatramio ilgį įrengus standžias jungtis. Taip pat atliekama standaus mazgo apspaudimo įtakos sijų įlinkiams analizė. Remiantis moksliniais straipsniais ir mokomosiomis knygomis nagrinėjami įvairūs standaus mazgo įrengimo konstrukciniai sprendiniai bei kontinualių sijų įrąžų ir įlinkių skaičiavimo metodai. Standžios jungties įtempių ir deformacijų būvis tiriamas baigtinių elementų metodu naudojant kompiuterinę statybinių konstrukcijų skaičiavimo programą LUSAS Analyst. Atlikus iš anksto įtemptų surenkamųjų gelžbetoninių sijų, sujungtų tarpusavyje standžiu mazgu, darbo analizę pateikiamos baigiamojo magistro darbo išvados ir pasiūlymai. Darbą sudaro 8 dalys: įvadas, standžių mazgų įrengimo ypatumai ir konstrukcinai sprendiniai, kontinualių sijų įrąžų ir įlinkių skaičiavimo metodai, standžių mazgų įrengimo įtakos sijų laikomajai galiai analizė, standžių mazgų įrengimo įtakos sijų įlinkiams analizė, standaus mazgo analizė baigtinių elementų metodu, išvados ir pasiūlymai, literatūros sąrašas. Darbo apimtis –... [toliau žr. visą tekstą] / The paper investigates precast prestressed beams and increase of their carrying capacity and decrease of deflections by providing rigid connections between adjascent spans. The analysis of carrying capacity includes relations between load capacity (herewith the sectional area of tensile reinforcement) and material properties of rigid connection, such as sectional area of continuity reinforcement and concrete grade. The analaysis of deflections investigates the reduction of beam height and increase of span length by providing moment continuity between adjascent spans. The effects of prestressing rigid connection is also discussed. Various moment continuity provision methods are reviewed. The stress-strain state of rigid connection is analysed by using finite element method. The conclutions and suggestions are made at the end of the thesis. The master thesis includes these parts: introduction, analysis of moment continuity provision methods, review of moment redistribution and deflection calculation methods, analysis of increased load carrying capacity after provision of moment continuity, analysis of decreased deflections after provision of moment continuity, rigid connection analysis using finite element method, conclusions and suggestions, references. Master thesis consists of – 77 p. text without appendixes, 24 pictures, 16 tables, 15 bibliographical entries.