The purpose of this thesis is to provide insight into how different geometric parameters such as tower height, girder depth, and pier dimensions influence the structural behaviour, cost, and feasibility of an extradosed bridge. A study of 51 extradosed bridges shows the variability in proportions and use of extradosed bridges, and compares their material quantities and structural characteristics to girder and cable-stayed bridges. The strategies and factors that must be considered in the design of an extradosed bridge are discussed. Two cantilever constructed girder bridges, an extradosed bridge with stiff girder, and an extradosed bridge with stiff tower are designed for a three span bridge with central span of 140 m. The structural behaviour, materials utilisation, and costs of each bridge are compared. Providing stiffness either in the girder or in the piers of an extradosed bridge are both found to be effective stategies that lead to competitive designs.

Span-to-depth ratio is an important bridge design parameter that affects structural behaviour, construction costs and aesthetics. A study of 86 constant-depth girders indicates that conventional ratios have not changed significantly since 1958. These conventional ratios are now questionable, because recently developed high-strength concrete has enhanced mechanical properties that allow for slenderer sections. Based on material consumption, cost, and aesthetics comparisons, the thesis determines optimal ratios of an 8-span highway viaduct constructed with high-strength concrete. Three bridge types are investigated: cast-in-place on falsework box-girder and solid slabs, and precast segmental span-by-span box-girder. Results demonstrate that total construction cost is relatively insensitive to span-to-depth ratio over the following ranges of ratios: 10-35, 30-45, and 15-25 for the three bridge types respectively. This finding leads to greater freedom for aesthetic expressions because, compared to conventional values (i.e. 18-23, 22-39, and 16-19), higher ranges of ratios can now be selected without significant cost premiums.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22414号 / 工博第4675号 / 新制||工||1729(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 河野 広隆, 教授 八木 知己 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

A large structural weldment has been designed to serve as the new star tracker bridge for the Dark Energy Experiment upgrade to the Hobby-Eberly Telescope at McDonald Observatory. The modeling approach, analysis techniques and design details will be of interest to designers of large structures where stiffness is the primary design driver. The design includes detailed structural analysis using finite element models to maximize natural frequency response and limit deflections and light obscuration. Considerable fabrication challenges are overcome to allow integration of precision hardware required for positioning the corrector optics to a precision of less than 5 microns along the 4-meter travel range. This thesis provides detailed descriptions of the bridge geometry, analysis results and challenging fabrication issues. / text

abstract: A comprehensive study was performed on non-proprietary ultra-high-performance concrete (UHPC) material and several design methods were suggested based on numerous experimental results. Several sets of compression tests, direct tensile tests, and flexural tests were performed on UHPC to provide a better understanding of the mechanisms involved in the mechanical behavior of the fiber reinforced material. In addition to compressive tests, flexural tests, based on ASTM C1609 and EN 14651, were performed. The effect of the strain rate on the UHPC material was also investigated through the high-speed tensile tests at different strain rates. Alongside the usual measurement tools such as linear variable differential transformers (LVDT) and clip gages, digital image correlation (DIC) method was also used to capture the full-range deformations in the samples and localized crack propagations. Analytical approaches were suggested, based on the experimental results of the current research and other research groups, to provide design solutions for different applications and design approaches for UHPC and hybrid reinforced concrete (HRC) sections. The suggested methods can be used both in the ultimate limit state (ULS) and the serviceability limit state (SLS) design methods. Closed form relationships, based on the non-linear design of reinforced concrete, were used in the calculation of the load-deflection response of UHPC. The procedures were used in obtaining material properties from the flexural data using procedures that are based on back-calculation of material properties from the experimental results. Model simulations were compared with other results available in the literature. Performance of flexural reinforced UHPC concrete beam sections tested under different types of loading was addressed using a combination of fibers and rebars. The same analytical approach was suggested for the fiber reinforced concrete (FRC) sections strengthened (rehabilitated) by fiber reinforced polymers (FRP) and textile reinforced concrete (TRC). The objective is to validate the proper design procedures for flexural members as well as connection elements. The proposed solutions can be used to reduce total reinforcement by means of increasing the ductility of the FRC, HRC, and UHPC members in order to meet the required flexural reinforcement, which in some cases leads to total elimination of rebars. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2018

The current assembly procedure to install a trunnion and hub into a bascule bridge girder involves cooling the trunnion in liquid nitrogen and shrink fitting it into the hub. The resulting trunnion-hub assembly is then allowed to warm to room temperature. Next, the trunnion-hub assembly is cooled in the liquid nitrogen and shrunk fit into the girder. The cooling of the trunnion does not cause any problems, however, when the trunnion-hub assembly is cooled in the liquid nitrogen, the hub experiences a large thermal shock. These thermal shocks induce large stresses into the hub, which has been known to cause it to crack. This study investigates an innovative assembly procedure to install the trunnion-hub assembly into a bascule bridge girder. To avoid cooling the trunnion-hub assembly, the girder was heated instead. Laboratory testing and finite element analysis were used to determine if the girder could reasonably be heated to install the trunnion-hub assembly. An experiment was conducted to analyze the heating process that will be used. A rectangular steel plate ( 60"x60x"0.75") was used to model the girder in the lab. Inductance-heating coils were used to heat the steel plate to 350°F. The heating process was recorded using a data acquisition system with thermocouples and strain gages. ANSYS was the finite element analysis (FEA) program that was used to model the heating process of the plate. The FEA results from ANSYS were compared with the experimental results. This confirmed the parameters of the finite element analysis were correct. Those parameters were then used to model a full-scale girder. The feasibility of heating the girder was determined from the finite element analysis results. It was determined that heating the girder with 2250 BTU over min for 90 minutes, was sufficient energy for the assembly procedure to work. The girder was heated to a maximum temperature of 350°F and a 0.015" clearance was created for the assembly of the trunnion-hub. The finite element analysis of the girder showed that the placement of the heating coils on the girder was critical. Therefore this innovative assembly procedure can easily be accomplished, however, each girder must first be analyzed to determine the optimal heating configuration.

In this thesis, new design concepts for arch bridges using ultra high-performance fibre-reinforced concrete are developed for spans of 50 to 400 m. These concepts are light-weight and efficient, and thus have the potential to significantly reduce the cost of construction. Lightness is achieved by the thinning of structural components and the efficient use of precompression in the arch, rather than by the decrease of bending stiffness. Using the advanced properties of the material, the design concepts were shown to reduce the consumption of concrete in arch bridges by more than 50% relative to arches built using conventional concrete technology. In addition to span length, other design parameters including span-to-rise ratio and deck-stiffening were considered, resulting in a total of seventy-two design concepts. Other important contributions made in this thesis include: (1) the development of a simple analytical model that describes the transition of shallow arches between pure arch behaviour and pure beam behaviour, (2) a comprehensive comparative study of 58 existing concrete arch bridges that characterizes the current state-of-the-art and serves as a valuable reference design tool, and (3) the development and experimental validation of general and simplified methods for calculating the capacity of slender ultra high-performance fibre-reinforced concrete members under compression and bending. The research presented in this thesis provides a means for designers to take full advantage of the high compressive and tensile strengths of the concrete and hence to exploit the economic potential offered by the material.

The use of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) in the construction industry started in the 1990s and has since then been used for bridges all over the world. The mechanical properties and the dense matrix result in lower material usage and superior durability compared to conventional concrete, but the implementation of UHPFRC in the Swedish industry has been delayed. The most evident explanation, based on interview with industry representatives, as to why UHPFRC is not commonly used in Sweden are due to the lack of standards and knowledge. UHPFRC also has a high cement content and the cement industry contributes with high carbon dioxide (CO2) emissions to the total CO2 emissions in the world. This MSc Thesis looks into if a UHPFRC bridge is a feasible alternative to a conventional reinforced concrete structure bridge from design and material usage perspectives, regarding reduction of CO2 emissions. The project’s overall goal is to increase the knowledge in Sweden about the material, regarding the production, mechanical properties and behaviour of UHPFRC, and the design, regarding the difference in design between UHPFRC and conventional concrete bridges. To examine the material, a UHPFRC mixture with short straight steel fibres was developed. Specimens were tested to see how the different fibre contents affect the mechanical properties and which fibre content that is most favourable. Three different fibre contents were tested: 1.5%, 2.0% and 2.5% of the total volume of the mixture. The tested and evaluated mechanical properties were workability, flexural strength, tensile strength, fracture energy, compressive strength and modulus of elasticity. This study does not contain tests of durability of UHPFRC, however trough the literature review it was investigated to what extent the fibres affect the durability. It was concluded that an increase in fibre content results in improved mechanical properties, except for workability and in some cases when using a fibre content of 2.5%. The increase in the mechanical properties is due to the increased cracking resistance and the bond strength between the fibres and the matrix. The decrease in the mechanical properties, e.g. characteristic tensile strength and compressive strength of cylinders, for 2.5% in fibre content can be due to uneven fibre distribution and higher amount of air in the specimens which result in less strength. It was concluded that 2.0% in fibre content is most favourable. It was possible to conclude that the degradation of the fibres takes a long time, however not to what extent the fibres will affect the durability. To evaluate if UHPFRC is a viable economical and environmental alternative to regular concrete bridges, three cases of bridge design are considered. Two cases with UHPFRC (different thickness) and one case with conventional concrete. Up to 2017 only technical guidelines and recommendations for design with UHPFRC existed, but in 2017 the first approved standards in the world were published. The French national standards cover material (NF P18-470, 2016) and design (NF P18-710, 2016) and were used for the design process. The material usage regarding the amount of reinforced UHPFRC/concrete and steel reinforcement as well as the amount of CO2 emissions from the production of cement and steel (fibre and steel reinforcement) used for the bridges in the mid-span and at the support were investigated. The design process was also evaluated. It was concluded that the UHPFRC bridge with an optimized thickness was 47% lighter than the conventional concrete bridge, but the amount of CO2 emissions was still higher (e.g. 23% from the support). To be able to determine if a UHPFRC bridge is a feasible alternative to a conventional concrete bridge, with regards to the reduction of CO2 emissions, the CO2 emissions have to be observed in a wider perspective than only from the production of cement and steel, e.g. fewer transports and longer lifetime. / Användningen av ultrahögpresterande fiberbetong (UHPFRC) i anläggningsindustrin började på 1990-talet och har sedan dess använts till broar i hela världen. De mekaniska egenskaperna och den täta UHPFRC matrisen resulterar i lägre materialanvändning och bättre beständighet i jämförelse med konventionell betong, men användningen av UHPFRC har inte slagit igenom i den svenska industrin. De största förklaringarna till varför UHPFRC sällan används i Sverige är för att det inte har funnits kunskap och standarder. UHPFRC har också en hög cementhalt och cementindustrin bidrar med höga koldioxid (CO2) utsläpp till de totala CO2 utsläppen i världen. Den här masteruppsatsen skrevs för att undersöka om en UHPFRC bro är ett möjligt alternativ till en konventionell betongbro ur dimensionering- och materialanvändningssynpunkt med avseende på reduktion av CO2 utsläpp. Projektets övergripande mål är att öka kunskapen om materialet, med avseende på tillverkningen, de mekaniska egenskaperna och beteendet av UHPFRC, och dimensionering, med avseende på skillnaden i dimensionering mellan UHPFRC broar och konventionella betongbroar. I materialdelen utvecklades ett UHPFRC recept med korta raka stålfibrer. Provkroppar testades för att se hur olika fiberinnehåll påverkade de mekaniska egenskaperna och vilket fiberinnehåll som var mest gynnsamt. Tre olika fiberinnehåll testades: 1.5%, 2.0% och 2.5% av total volym av blandningen. De mekaniska egenskaperna som testades och utvärderades var bearbetbarheten, böjhållfasthet, draghållfasthet, fraktur energi, tryckhållfasthet och elasticitetsmodul. Beständigheten av UHPFRC testades aldrig men i vilken omfattning fibrerna påverkar beständigheten undersöktes i den litteraturstudie som skrevs inför testerna och tillverkningen av UHPFRC. Det konstaterades att en ökning i fiberinnehåll resulterade i en ökning av de mekaniska egenskaperna, förutom för bearbetbarheten och i vissa fall när ett fiberinnehåll av 2.5% användes. Ökningen av de mekaniska egenskaperna berodde på det ökande sprickmotståndet och bindningsstyrka mellan fibrerna och matrisen. Minskningen av de mekaniska egenskaperna, till exempel den karakteristiska drag- och tryckhållfastheten, när ett fiberinnehåll på 2.5% i cylindrar användes kan bero på ojämn fiberfördelning och större mängd luft i provkropparna vilket resulterar i lägre hållfasthet. Det konstaterades att ett fiberinnehåll på 2.0% var det mest gynnsamma. Det kunde inte konstateras i vilken omfattning fibrerna påverkar beständigheten men det kunde konstateras att nedbrytningen av fibrerna tar lång tid. I dimensioneringsdelen utformades tre slakarmerade balkbroöverbyggnader, i två fall var överbyggnaden med UHPFRC (olika tjocklekar) och i ett fall var den med konventionell betong. Fram till 2017 fanns det bara tekniska riktlinjer och rekommendationer för UHPFRC men 2017 publicerades de första godkända standarderna i världen. De franska nationella standarderna täcker material (NF P18-470, 2016) och dimensionering (NF P18-710, 2016) och användes vid dimensioneringen. Materialanvändningen med avseende på mängd armerad UHPFRC/betong och slakarmering och mängd CO2 utsläpp från produktionen av cement och stål (fibrer och slakarmering) som användes till broarna i mittenspannet och vid stöden undersöktes. Även dimensioneringsprocessen utvärderades. Det konstaterades att UHPFRC bron med optimerad tjocklek var 47% lättare än betongbron men mängden CO2 utsläpp var fortfarande högre (till exempel 23% högre från stödet). Det konstaterades att om det ska vara möjligt att fastställa att en UHPFRC bro är ett möjligt alternativ till en konventionell betongbro, med avseende på reduktion av CO2 utsläpp, måste CO2 utsläppen ses från ett bredare perspektiv än från bara produktion av cement och stål, till exempel mindre transporter och längre livslängd.

In this thesis, new design concepts for arch bridges using ultra high-performance fibre-reinforced concrete are developed for spans of 50 to 400 m. These concepts are light-weight and efficient, and thus have the potential to significantly reduce the cost of construction. Lightness is achieved by the thinning of structural components and the efficient use of precompression in the arch, rather than by the decrease of bending stiffness. Using the advanced properties of the material, the design concepts were shown to reduce the consumption of concrete in arch bridges by more than 50% relative to arches built using conventional concrete technology. In addition to span length, other design parameters including span-to-rise ratio and deck-stiffening were considered, resulting in a total of seventy-two design concepts. Other important contributions made in this thesis include: (1) the development of a simple analytical model that describes the transition of shallow arches between pure arch behaviour and pure beam behaviour, (2) a comprehensive comparative study of 58 existing concrete arch bridges that characterizes the current state-of-the-art and serves as a valuable reference design tool, and (3) the development and experimental validation of general and simplified methods for calculating the capacity of slender ultra high-performance fibre-reinforced concrete members under compression and bending. The research presented in this thesis provides a means for designers to take full advantage of the high compressive and tensile strengths of the concrete and hence to exploit the economic potential offered by the material.

Several of the bridges along the Bothnia railway line do not fulfill the requirements regarding vertical accelerations that are stated in current design codes. The acceleration of the bridges needs to be reduced, in order to make the Bothnia line suitable for high speed railway traffic. The aim with this thesis is to investigate if it is possible to reduce the vertical acceleration of insufficient bridges to an acceptable level by using post-installed dampers. The expectation was that this method could have major economic advantages compared to other rehabilitation methods. Five different bridges with post-installed dampers were simulated in verified MATLAB codes. The simulations were performed for two cases for each bridge: one where the eccentricities between the attachment of the damper and the centre of gravity of the bridge cross section was taken into consideration, and one where the influence from the eccentricities was excluded. The results showed that it is fully possible to reduce the acceleration to an acceptable level with the use of external damper configurations. It was also shown that the eccentricities of the bridges had a high impact in this kind of simulations. Furthermore, some supplementary investigations regarding the location and position of the damper, were done as well. Finally, a brief analysis and discussion regarding the practical implementation of the post-installed was performed. One challenge is to anchor the damper and take care of the resulting forces in a favourable and safe way. / Flertalet broar längs med Botniabanan uppfyller inte de krav som ställs på de vertikala accelerationsnivåerna i gällande dimensioneringsnormer. Dessa accelerationer måste reduceras för att göra Botniabanan tillgänglig för trafik med höghastighetståg. I denna uppsats undersöks det huruvida det är möjligt att sänka accelerationen i bristfälliga broar med hjälp av eftermonterade externa dämpare. Förväntningen var att denna metod skulle ha stora ekonomiska fördelar gentemot andra upprustningsmetoder. Fem broar med eftermonterade dämpare har simulerats i verifierade MATLAB-koder. Simuleringarna utfördes på två olika sätt för varje bro: i en kod togs eccentriciteten mellan dämparinfästningen och tyngdpunktslinjen för bron i beaktande, och i den andra koden försummades all inverkan av eccentriciteten. Resultatet från simuleringarna visade att det är fullt möjligt att reducera accelerationerna till en acceptabel nivå med hjälp av externa dämpningskonfigurationer. Eccentriciteten visade sig även ha stor inverkan på resultatet i denna typ av simulering. Dessutom utfördes några kompletterande undersökningar gällande längd, position och vinkel på dämparen. Slutligen analyserades och diskuterades den praktiska implementeringen av de eftermonterade dämparna. En utmaning är att förankra dämparna och föra ner de resulterande krafterna på ett fördelaktigt och säkert sätt.