Steel straps are being used for confinement purposes of steel-free bridge deck slab. The objective of this study was to use GFRP prestressed concrete straps as an alternative to steel straps, and assess the effect of the alkaline concrete environment on the long-term performance of GFRP. Each strap was 160 x100 mm2 in cross section, 2000 mm in length and pre-tensioned with two 16 mm diameter GFRP strands. The experimental study included testing three sets of concrete straps, pre-stressed at 35%, 45%, and 55% of ultimate strength of GFRP. The straps were tested in tension after being subjected to temperatures from -25oC to +40 oC in an environmental chamber. Another two sets of straps were cast and tested two and a half years later. The control and conditioned samples achieved comparable results proving that GFRP can withstand prestressing levels higher than 25% and up to 35% of their ultimate strength.

Steel straps are being used for confinement purposes of steel-free bridge deck slab. The objective of this study was to use GFRP prestressed concrete straps as an alternative to steel straps, and assess the effect of the alkaline concrete environment on the long-term performance of GFRP. Each strap was 160 x100 mm2 in cross section, 2000 mm in length and pre-tensioned with two 16 mm diameter GFRP strands. The experimental study included testing three sets of concrete straps, pre-stressed at 35%, 45%, and 55% of ultimate strength of GFRP. The straps were tested in tension after being subjected to temperatures from -25oC to +40 oC in an environmental chamber. Another two sets of straps were cast and tested two and a half years later. The control and conditioned samples achieved comparable results proving that GFRP can withstand prestressing levels higher than 25% and up to 35% of their ultimate strength.

No description available.

O conceito de pontes de madeira em tabuleiro laminado protendido surgiu na década de 70, no Canadá, como forma de reabilitação para tabuleiros laminados pregados. Diversas pesquisas foram desenvolvidas para verificar o desempenho estrutural e a durabilidade do sistema, e estes estudos comprovaram a eficácia do método. Devido ao enorme déficit de pequenas e médias pontes em todo o seu território, o Brasil tem buscado cada vez mais materiais e tecnologias alternativas economicamente competitivas para sua construção. Partindo de pesquisas desenvolvidas em outros países, desde 1993 começaram a ser desenvolvidas pesquisas nacionais para verificar a viabilidade em se utilizar madeiras brasileiras para construção de pontes, e a resposta, mais uma vez, foi positiva. Este trabalho tem como objetivos o estudo teórico e experimental das pontes de eucalipto protendidas transversalmente, através do projeto e construção da primeira ponte protendida de madeira da América do Sul. Por meio de provas de carga, foi avaliado o desempenho da ponte e a influência dos guarda-rodas e defensas na rigidez do tabuleiro. Os resultados mostram que o sistema protendido de eucalipto é uma ótima alternativa para o Brasil. / The concept of pre-stressed laminated timber bridges come from 70s, in Canada, as an alternative for the rehabilitation of damaged nailed laminated timber decks. Many researches were developed to verify the structural performance and the durability of the system, which corroborated the system\'s high efficience. Because of a great deficit in short-span and medium-span bridges in Brazil, the country has searched more and more competitive materials and technologies for their construction. Based on studies developed in other countries, since 1993 Brazil has developed studies to verify the viability of using brazilian woods to build such bridges, and the answer was positive. The present work aims to investigate the project and behavior of transversally pre-stressed timber bridges of eucalyptus, through the project and construction of the first stress-laminated timber bridge in South America. The bridge performance was evaluated as well as the influence of the guard-rail system in the deck stiffness, across proof loading. The results showed that this system is a good alternative for bridge construction in Brazil.

O conceito de pontes de madeira em tabuleiro laminado protendido surgiu na década de 70, no Canadá, como forma de reabilitação para tabuleiros laminados pregados. Diversas pesquisas foram desenvolvidas para verificar o desempenho estrutural e a durabilidade do sistema, e estes estudos comprovaram a eficácia do método. Devido ao enorme déficit de pequenas e médias pontes em todo o seu território, o Brasil tem buscado cada vez mais materiais e tecnologias alternativas economicamente competitivas para sua construção. Partindo de pesquisas desenvolvidas em outros países, desde 1993 começaram a ser desenvolvidas pesquisas nacionais para verificar a viabilidade em se utilizar madeiras brasileiras para construção de pontes, e a resposta, mais uma vez, foi positiva. Este trabalho tem como objetivos o estudo teórico e experimental das pontes de eucalipto protendidas transversalmente, através do projeto e construção da primeira ponte protendida de madeira da América do Sul. Por meio de provas de carga, foi avaliado o desempenho da ponte e a influência dos guarda-rodas e defensas na rigidez do tabuleiro. Os resultados mostram que o sistema protendido de eucalipto é uma ótima alternativa para o Brasil. / The concept of pre-stressed laminated timber bridges come from 70s, in Canada, as an alternative for the rehabilitation of damaged nailed laminated timber decks. Many researches were developed to verify the structural performance and the durability of the system, which corroborated the system\'s high efficience. Because of a great deficit in short-span and medium-span bridges in Brazil, the country has searched more and more competitive materials and technologies for their construction. Based on studies developed in other countries, since 1993 Brazil has developed studies to verify the viability of using brazilian woods to build such bridges, and the answer was positive. The present work aims to investigate the project and behavior of transversally pre-stressed timber bridges of eucalyptus, through the project and construction of the first stress-laminated timber bridge in South America. The bridge performance was evaluated as well as the influence of the guard-rail system in the deck stiffness, across proof loading. The results showed that this system is a good alternative for bridge construction in Brazil.

Diploma thesis deals with design pre-stressed road bridge over the local brook and field road. There are designed 3 studies, from which variation trapezial point-supported pre-stressed concrete slabroad bridge with 3 spans is chosen. In the structural analysis of the bridge structure is assessed at the ultimate limit state and serviceability by European standards – Eurocodes. It is developed drawings and visualization of the bridge.

Prefabricated and pre-stressed reinforced concrete beams and girders are integral components of many highway structures, including those built by rapid construction techniques. Concerns exist regarding the development of cracks during curing, form removal, detensioning, transport, installation, and operation. Non-destructive, Acoustic Emission (AE) sensing techniques have the potential for detecting and locating cracking in prefabricated, pre-stressed concrete girders used as Prefabricated Bridge Elements and Systems (PBES) used in rapid construction practices as part of a Quality Assurance/Quality Control (QA/QC) program. AE sensing records transient elastic waves produced by the release of stored elastic energy resulting in plastic deformations (i.e., crack nucleation and growth) with an array of point sensors. The AE instrument system is relatively portable which can allow for it to be an option for both off-site fabrication QA/QC as well as on-site field QA/QC. This thesis presents a multi-stage research initiative on acoustic emission monitoring of prefabricated and pre-stressed reinforced concrete beams used in highway bridge construction during detensioning, craned removal from formwork and transport to bridge sites, along with supporting laboratory tests and numerical analysis. The specific objectives of this research were to: 1. Identify suitable instruments to monitor pre-stressed and/or post-tensioned concrete girders for cracking activity; 2. Design and develop a reusable instrumentation package; 3. Measure performance and condition of concrete girders during fabrication and transport; and 4. Identify test protocols and possible accept/fix/reject criteria for structural elements based on information from monitoring system. Presented are results from laboratory, full-scale girder fabrication, and transport monitoring, along with overall conclusions and recommendations for future research.

Abstract Many electrical devices already surround us in our everyday life. Some devices monitor car performance and traffic while others exist in handheld devices used by the general public. Electrical devices also control manufacturing processes and protect workers from exposure to hazardous working environment. All these devices require electricity to operate. This exponential growth of low power electronic devices in industry, healthcare, military, transportation and in portable personal devices has led to an urgent need for system integrated energy sources. Many energy harvesting technologies have been developed to serve as a power source in close proximity to the electrical device itself. Solar and magnetic energy harvesters are the most common solutions when conditions are suitable. A more recent technique, called piezoelectric energy harvesting, has raised significant interest among scientists and in industry. Through piezoelectric (ceramic) material mechanical energy can be harvested and converted to electrical energy. This method requires accurate analysis of the kinetic energy experienced by the piezoelectric material so that the mechanics can be suitably designed. At the same time the mechanical design has to protect the piezoelectric material from intense forces that might cause cracks, while still transmitting the kinetic energy efficiently. These requirements usually mean a specific energy harvest design for each ambient energy source at hand. This thesis is focused on energy harvesting from low frequency compressions using piezoelectric ceramic materials. The objective was to manufacture, measure and implement structures that could sustain the forces experienced under the heel of a foot and maximize the harvested energy amount and efficiency. Two different construction designs were developed and optimised with an iterative process. The kinetic energy impulse under the heel part of the foot was studied by measuring the electrical output of the harvester during walking and then analysed with modelling software. The results were used to create a walking profile for a computer controlled piston to study the input energy phase, speed and force influence on the amount of the harvested energy and the efficiency of the harvesting process. Finally, the functionality of the concept was tested in a real environment with an energy harvester inserted inside a running shoe. The developed harvester showed the highest energy density reported in this frequency region. / Tiivistelmä Monet elektroniset laitteet ympäröivät meitä jokapäiväisessä elämässä. Ne tarkkailevat auton toimintaa tai liikennettä ja toiset toimivat aina mukana kulkevissa kannettavissa laitteissa. Töissä ne valvovat valmistusprosesseja tai varoittavat työntekijöitä vaarallisista työolosuhteista. Kaikki nämä laitteet tarvitsevat sähköä toimiakseen. Pienitehoisten elektronisten laitteiden eksponentiaalinen kasvu teollisuudessa, terveyssektorilla, puolustusteollisuudessa, kulkuneuvoissa sekä kannettavassa kulutuselektroniikassa on johtanut suureen tarpeeseen kehittää järjestelmiin integroituja energialähteitä. Monia energiankeräystekniikoita on kehitetty toimimaan elektronisten laitteiden läheisyydessä. Aurinkopaneelit ja magneettiset energiankeräysmenetelmät ovat yleisimpiä ratkaisuja, jos olosuhteet antavat siihen mahdollisuuden. Pietsosähköinen energiankeräys on uudempi tekniikka, joka on herättänyt kasvavaa huomiota tutkimusyhteisössä sekä teollisuudessa. Pietsosähköisen materiaalin avulla mekaaninen energia voidaan muuntaa suoraan sähköiseksi energiaksi. Tässä tekniikassa kineettinen energia tulee analysoida tarkasti mekaniikka suunnittelua varten, jotta se saadaan kohdistettua tehokkaasti pietsosähköiseen materiaaliin. Lisäksi mekaniikan tulee suojata materiaalia voimilta, jotka voivat johtaa murtumiin. Näistä vaatimuksista johtuen jokainen ulkoinen energialähde vaatii yleensä yksilöllisen energiankeräysrakenteen. Tämä väitöstyö keskittyy pietsosähköisten keraamien hyödyntämiseen energiankeräyksessä matalataajuisista mekaanisista voimista. Tarkoituksena oli suunnitella, valmistaa, mitata ja asentaa rakenteita, jotka kestävät kantapäähän kohdistuvia voimia kävelyn ja juoksun aikana sekä maksimoida talteen saatava energia ja hyötysuhde. Kaksi erilaista rakennetta suunniteltiin, valmistettiin ja optimoitiin energiankeräystä varten. Kantapäähän kohdistuva kineettinen energia analysoitiin mallinnusohjelmistolla ja mittaamalla sähköinen vaste energiakeräys rakenteesta. Tuloksien avulla suunniteltiin kävelyprofiilia imitoiva mekaaninen männän liike, jonka avulla tutkittiin kohdistettavan voiman nopeuden, vaiheen ja suuruuden vaikutusta energiankeräyksen hyötysuhteeseen ja saatavaan tehoon. Viimeisenä energiankeräysrakenteen toimivuutta testattiin oikeassa ympäristössä asentamalla se juoksukenkään. Kehitetyllä pietsosähköisellä energiakeräimellä saavutettiin korkeimmat raportoidut energiatiheydet käytetyllä taajuusalueella.

This thesis deas with dynamic analysis of pneumatic actuator which is used as regulation mechanis of turbochargers with Variable Nozzle Turbine (VNT) technology. The first part of work is focused on experimental modeling which goal is obtaining Frequency Response Function on specify frequency range by Frequency Response Function Analysis – FRFA. Dominant vibrations of pneumatic actuator active parts is expected on this specify frequency range. Results of experimental modeling will be used for gaining input parameters for numerical computation as well. The second part deal with Pre-Stressed Modal Analysis and subsequently Harmonic analysis. Obtained results with numerical and experimental analysis will be compared. This part of diploma thesis is solved in programmatic environment ANSYS Workbench.

The global understanding that natural resources and non renewable energy sources are not inexhaustible has been growing lately together with the increase of conscientiousness on the consequences that our demanding way of life has on the environment. Global warming, ozone layer depletion, the greenhouse effect or the acid rain, are some of these consequences, which may reach catastrophic levels if nothing is done to emend the actual situation. Lately, society is beginning to see sustainability not only as a needed requirement but as a distinctive value which has to be pursued by the different areas of society involved and responsible for a sustainable development such as public administration and companies, engineers and researchers. As a fundamental part of society, infrastructures have utmost importance in sustainable development. Even more when it comes to rail transport infrastructure, given the important role of rail transport in the development of a sustainable society. That is why engineers should make an effort to use all the tools available to choose the best structural design, which not only meets structural requirements, but has also a good performance for the environment. To do so, engineers must focus on using renewable sources or energy and materials, increasing the life of the existing infrastructures, making them more durable. When it comes to railway bridges, it is preferable to reuse and adapt existing structures than tear them down to build new ones. In this line, environmental assessment methodologies provide an incredibly valuable tool for help decision-makers and engineers to identify and select the best alternative design regarding environmental issues. Therefore, it is important to count on a common basis and established criteria together with a systematic methodology in order to obtain reliable results to compare alternatives and make the right decisions. However, nowadays, there exists very little guidance to perform this kind of analysis, and an extensive variety of databases and methodologies non standardized, which leads to uncertainties when it comes to evaluate and compare the obtained results. This thesis means to be a good guide for engineers, when performing a Life Cycle Assessment of a railway bridge, and to become a useful tool to compare several alternatives to identify the best option relating the environmental burdens involved. With this purpose, in order to know the state of the art of LCA methodology, it has been studied a wide range of existing literature and previous studies performed to analyze bridges and building materials. Finally, it has been developed an own methodology based on all the research done before, and implemented in an Excel application program based on Visual Basic macros, which means to be easy to use with a simple user interface, and to provide reliable results. The application is useful for assessing, repair or improving existing bridges, where the amounts of materials and energy are known, but can also be helpful in the design phase to compare different alternatives. It also allows using different weighting methodologies according to several reference sources depending on the case of study. The application is tested by carrying out a Life Cycle Assessment of a Spanish railway bridge located in the city center of Vitoria-Gasteiz, evaluating the different structures that conform the bridge system thorough all the stages of its life cycle identifying the most contributive parameters to the environmental impacts. The study was carried out over a 100 year time horizon. In the case of performing the LCA of this particular bridge, the contribution of the whole bridge is taken into consideration. When comparing two different bridges, the application has the option to compare them in the same basis, dividing by length and width of the bridge, which is a helpful tool if both bridges are not the same size. All stages of the life cycle were considered: the material stage, construction, the use and maintenance stage, and the end of life. The material stage includes the raw material extraction, production and distribution. The construction stage accounts the diesel, electricity and water consumption during construction activities. The use and maintenance stage covers the reparation and replacing operations. And the end of life covers several scenarios. In this case of study, in order not to interrupt the rail traffic, the bridge was constructed parallel to its final location, and then moved into the right place with hydraulic jacks. This leads to an important auxiliary structure with its own foundations, which has a significant contribution to the overall environmental impact. The scenario chosen for the end of life was based on similar actuation in other constructions in the proximities of the bridge, as the bridge is already in use. These assumptions were to recycle 70 % of the concrete and 90 % of the steel; all the wood used for formwork was disposed as landfill. The results obtained, weighted according to the US Environmental Protection Agency, shows that the main contributor to the environmental impacts is the material phase, with the 64 % of the total weighted results with concrete and steel production as principal factors, followed by timber production. These processes account great amounts of CO 2emissions, which makes essential to focus on reducing the impact of the material processes by optimizing the processes but mainly by reusing materials from other constructions as much as it may be possible. The maintenance activities have some importance due to the frequency of the track replacement, assumed to be once every 25 years. While construction does not imply great burdens for the environment, the end of life causes the 33 % of the overall bridge impact. This is due to the timber formwork disposal as landfill and to a lesser extent because of the recycling of the steel. The timber disposal increases widely the eutrophication effect, and will be easy to be reused in further constructions. Regarding the different parts of the bridge structure, the auxiliary structure has an important contribution with the 61 % of the overall weighted impact. As it is a concrete bridge, both the substructure and superstructure has similar contribution. The substructure has a slightly higher impact with the 21 % and the superstructure the 15 %. Rail structure and transport have very little contribution.