Accelerated Bridge Construction (ABC) techniques have resulted in innovative options that save time and money during the construction of bridges. One such group of techniques that has generated considerable interest is the usage of individual precast concrete members. Utilizing precast concrete decks allows for offsite curing, thus eliminating long delays due to formwork and concrete curing time. These precast concrete decks have inherent joints between the individual panels. These joints are locations for potential leakage, which can lead to corrosion or inadequate long-term performance. Post-tensioning the precast deck panels helps to eliminate leakage; however, conventional longitudinal post-tensioning systems require complete deck replacement in the event of a single faulty deck panel. A proposed post-tensioned, curved-strand connection allows for a single panel to be replaced. The capacity of the proposed curved-strand connection was investigated in order to compare its behavior to other systems that are currently in use. Tests were performed in composite negative bending, beam shear, and positive bending. The curved strand connection was found to behave similarly to the standard post-tensioning system in positive bending and shear. The curved-strand connection was found to be comparable to a standard post-tensioning system. The ultimate capacity of the curved-strand connection in negative bending was found to be 97% of the standard post-tensioning. Pre-stress losses were measured and predicted for the service life of the connection and were found to be 6% at the 75- year service life of a bridge.

Closure joints are used in precast bridge construction to join two pieces of precast concrete. The pieces of concrete are joined by a lap splice which consists of longitudinal steel sticking out of each precast element and overlapped over the minimum required development length. State departments of transportation find it desirable to make the width of closure joints short. To achieve this, bridge engineers have been using hooked bars in the closure joints in lieu of straight bars, with the assumption that this would allow for shorter splice lengths. Though engineers in practice are doing this, design guidance does not exist. One research project by Coleman (2024) tested 58 beam-splice specimens to investigate the impacts of a variety of parameters on bond and anchorage and develop design guidance for hooked bar lap splices. This project did not investigate three parameters: the number of lap splices, the placement of transverse reinforcement, and the addition of steel fibers in the closure joint. For this thesis, 15 beam-splice specimens were tested in 4 point-bending to investigate the impact of these parameters on bond and validate the descriptive equation developed by Coleman (2024) to determine the bar stress of a hooked bar lap splice. The findings of this study suggest that the number of splices and the placement of transverse reinforcement has minimal impact on the bar stress developed, and the equation by Coleman (2024) adequately predicts the bar stress when these parameters were varied. The addition of steel fibers to the closure joint had a substantial impact on increasing the splice strength. In the beams where steel fibers were added in a 1% fiber volume fraction, the descriptive equation by Coleman (2024) underpredicted the bar stress for both unconfined and confined beams with the addition of fibers. Thus, this thesis proposes a factor to multiply the descriptive equation by determining the bar stress when steel fibers are added. With these findings, using steel fibers in closure joints for precast concrete can be used to reduce splice length in non-contact hooked bar lap splices. / Master of Science / Precast concrete is concrete that is cast off-site in a controlled environment and transported to the site to then be put together at the site of a project. In bridge construction, this is very beneficial to projects since it means that there is more quality control of the specimens and can allow for faster construction times since the components can have time to cure to strength off-site. To put together pieces of precast concrete to create continuous beams and other components, a closure joint is used. These closure joints consist of two precast pieces of concrete which have longitudinal steel sticking out of each precast element. The pieces of concrete are then joined by overlapping the longitudinal steel in a lap splice. Where a lap splice is used to develop the minimum development, length is required to provide the adequate bar strength such that load will be transferred from one beam to another to create a continuous beam. State departments of transportation find it desirable to make the width of closure joints short. Since closure joint width is typically controlled by the minimum development length required to connect the pieces of concrete, the main way to reduce the width is to reduce the minimum development length. To achieve this, bridge engineers have been using hooked bars in the closure joints in lieu of straight bars, with the assumption that this would allow for shorter splice lengths. Though engineers in practice are doing this, design guidance does not exist. One research project by Coleman (2024) tested 58 beam-splice specimens to investigate the impacts of a variety of parameters on bond and anchorage and develop design guidance for hooked bar lap splices. This project did not investigate three parameters: the number of lap splices, the placement of transverse reinforcement, and the addition of steel fibers in the closure joint. For this thesis, 15 beam-splice specimens were tested in 4 point-bending to investigate the impact of these parameters on bond and validate the descriptive equation developed by Coleman (2024) to determine the bar stress of a hooked bar lap splice. The findings of this study suggest that the number of splices and the placement of transverse reinforcement has minimal impact on the bar stress developed, and the equation by Coleman (2024) adequately predicts the bar stress when these parameters were varied. The addition of steel fibers to the closure joint had a substantial impact on increasing the splice strength. In the beams where steel fibers were added in a 1% fiber volume fraction, the descriptive equation by Coleman (2024) underpredicted the bar stress for both unconfined and confined beams with the addition of fibers. Thus, this thesis proposes a factor to multiply the descriptive equation by determining the bar stress when steel fibers are added. With these findings, using steel fibers in closure joints for precast concrete can be used to reduce splice length in non-contact hooked bar lap splices.

The interstate highway system is vitally dependent upon current and future bridges. These bridges must be designed economically to continue the serviceability with limited maintenance. For precast bridge construction a portion of the design must consider the bridge connections. Some current connections have proved insufficient in serviceability as there is uncontrolled cracking. In other connections there are uncertainties in the calculations (or lack of calculations) which require design guidelines. This thesis presents design recommendations for precast decking u-bar reinforcement in tension which results from negative moment over a pier. Testing results from the University of Tennessee were analyzed to determine the design recommendations. The calculated capacity of the specimens was determined first by strut and tie modeling by AASHTO and ACI, but was shown to be insufficient. Proposed changes to the current calculation of the strut width as specified in AASHTO and ACI STM methods were discussed in order to match the test results. However, strut and tie modeling demonstrated that the design for the lacer bar was inadequate. Since the strut and tie modeling method resulted in an inaccurate lacer bar size, another method was developed. A triangular shape develops from the flow of forces in the connection joint zone; as a result, a free body diagram (FBD) was developed from the concrete triangular shape. This diagram showed how the forces flow in the in-situ joint as well as how they are resisted. A formula was developed from the FBD to determine the capacity of the joint which accurately reflected the capacities from tests. A FBD was also made of the lacer bar utilizing the forces and geometry calculated from the capacity calculations. A computer analysis program was used to determine the forces in the lacer bar. The lacer bar could then be designed since the required forces to resist (moment and shear) were known. A comparison of the strut and tie model to the triangular method led to the conclusion that both can determine the longitudinal reinforcement spacing, joint overlap length, and concrete strength, but only the triangular method can determine a more sufficient lacer bar size.

SammanfattningSvensk järnväg har aldrig varit mer belastad och trafikerad än idag, och värre kommer det att bli. Det har inte pågått några större investeringar i svensk järnväg sen 1990-talet, effekterna av den strategin börjar bli alltmer uppenbar. Sveriges järnvägssystem i jämförelse med många europeiska länder och även utanför Europa är teknologiskt och innovativt undermålig. Höghastighetståg som överstiger 250 km/h är ännu bara ett koncept i Sverige medan i länder som Frankrike, Tyskland, Kina och Japan är detta sen flera år tillbaka en verklighet. Det finns framträdande fördelar med etableringen av höghastighetsjärnväg som överstiger hastigheter på 250km/h. Utbyggnaden av höghastighetsjärnväg medför ett avsteg från konventionella järnvägsmetoder så som banvallar, i stället används prefabricerade broelement som möjliggör fast gjutning av spåret och utan användningen av ballast. Denna metod banar väg för högre tåghastigheter, mindre underhållsåtgärder, längre livslängd, passager under bron av befintlig transportinfrastruktur och besparing av natur och djurliv. Ovannämnda länder har kunnat omdirigera trafikbelastning på övriga transportsystem så som vägar och inrikes flygresor. En mindre belastning på exempelvis vägnätverket, leder till bättre trafikförhållanden, mindre slitage på vägbana och därmed sänkta kostnader för underhåll. Ur ett miljö- och hållbarhetsperspektiv minskar även utsläppet av farliga gaser och partiklar så som koldioxid, samt dämpar konsumtionen av fossila bränslen till fossildrivna fordon. Syftet med examensarbetet är att lyfta fördelarna med utbyggnaden av höghastighetsjärnväg i Sverige. Där fokus ligger i att göra detta genom att frångå den konventionella metoden av banvallar och i stället implementera brobanor med dess många framträdande fördelar. Arbetet genomsyras av utländska perspektiv gällande utbyggnad och underhåll, där höghastighetsjärnväg förlagd på bro används i större omfattning. Detta medför att arbetet kan erbjuda relevanta perspektiv från länder som exempelvis Kina som är världsledande inom området. Förhoppningen är att arbetet ska kunna användas som underlag för framtida järnvägsprojekt i Sverige. Resultatet för rapporten innehåller tre delar, kostnad, underhållsåtgärder samt miljö- och hållbarhetsperspektiv. Arbetet har redogjort för en grov kostnadsindikation på vad det kan kosta att bygga 1 km broförlagt ballastfritt dubbelspår, slutkostnaden hamnade på 929 miljoner kr med en standardavvikelse på ± 30 %. Underhåll av höghastighetsjärnväg på brobanor påvisas av många länder vara minimal. Det som möjliggör detta är innovativ detekteringsteknologi som regelbundet återger skick och funktionsduglighet av såväl banan som bron. Brobanor konstrueras för långa livslängder, det slitage som uppstår är generellt kopplat till rälsslipning och så kallade kritiska punkter vid sammanfogning av prefabricerade broelementen där det finns större risk för sprickbildning med mera. / Swedish railways have never been more congested than today, and it will get worse. There has been no major investment in Swedish railways since the 1990s, and the effects of that strategy are becoming increasingly apparent. Sweden's railway system, compared to many European countries and even countries outside Europe, is technologically and innovatively inferior. High-speed trains exceeding 250 km/h are still only a concept in Sweden, whereas in countries such as France, Germany, China, and Japan this has been a reality for several years. There are prominent advantages to the establishment of high-speed rail exceeding speeds of 250km/h. The development of high-speed rail involves a departure from conventional railway methods such as embankments, instead using prefabricated bridge elements that allow for the fixed casting of the track and without the use of ballast. This method paves the way for higher train speeds, less maintenance, longer service life, passage under the bridge of existing transport infrastructure, and conservation of nature and wildlife. The above-mentioned countries have been able to redirect traffic loads from other transport systems such as roads and domestic air travel. Less strain on the road network, leads to better traffic conditions, less wear and tear on the road surface and thus reduced maintenance costs. From an environmental and sustainability perspective, it also reduces emissions of hazardous gases and particulates such as carbon dioxide and curbs the consumption of fossil fuels by fossil fuel powered vehicles.The aim of the thesis is to highlight the benefits of the expansion of high-speed rail in Sweden. The focus is to do this by abandoning the conventional approach of embankments and instead implementing bridge lanes with its many prominent advantages. The work is permeated by foreign perspectives regarding development and maintenance, where high-speed rail on bridges is more widely used. This means that the work can offer relevant perspectives from countries such as China, which is world leading in this field. It is hoped that the work can be used as a basis for future railway projects in Sweden. The result of the report contains three parts, cost, maintenance measures and environmental and sustainability perspectives. The work has given a rough cost indication of what it might cost to build 1 km of bridge-laid ballastless double track, the final cost ended up at 929 million SEK with a standard deviation of ± 30%. Maintenance of high-speed rail on bridge tracks is shown by many countries to be minimal. This is made possible by innovative detection technology that regularly reproduces the condition and operability of both the track and the bridge. Bridge decks are designed for long lifetimes, the wear and tear that occurs is generally related to rail grinding and so-called critical points in the joining of prefabricated bridge elements where there is a higher risk of cracking etc.

The main aim of the present study is to evaluate the safety level of Turkish type precast prestressed concrete bridge girders designed according to American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) based on reliability theory. Span lengths varying from 25 m to 40 m are considered. Two types of design truck loading models are taken into account: H30S24-current design live load of Turkey and HL93-design live load model of AASHTO LRFD. The statistical parameters of both load and resistance components are estimated from local data and published data in the literature. The bias factors and coefficient of variation of live load are estimated by extrapolation of cumulative distribution functions of maximum span moments of truck survey data (Axle Weight Studies) that is gathered from the Division of Transportation and Cost Studies of the General Directorate of Highways of Turkey. The uncertainties associated with C40 class concrete and prestressing strands are evaluated by the test data of local manufacturers. The girders are designed according to the requirements of both Service III and Strength I limit states. The required number of strands is calculated and compared. Increasing research in the field of bridge evaluation based on structural reliability justifies the consideration of reliability index as the primary measure of safety of bridges. The reliability indexes are calculated by different methods for both Strength I and Service III limit states. The reliability level of typical girders of Turkey is compared with those of others countries. Different load and resistance factors are intended to achieve the selected target reliability levels. For the studied cases, a set of load factors corresponding to different levels of reliability index is suggested for the two models of truck design loads. Analysis with Turkish type truck models results in higher reliability index compared to the USA type truck model for the investigated span lengths

This thesis deals with building survey of bridge register number 43-011 located near Česká. The part of thesis is literary reaserch dealing with system of management and cotrol of road bridges, precast bridge contructions made with DS-C type girgers and about general diagnostical methods. The practical section contains of in situ diagnostical survey and bridge inspection, laboratory evaluation and comparision, load bearing capacity calculation and suggestion of potencional technical precautions.