17,810 research outputs found
Guidelines for data collection and monitoring for asset management of New Zealand road bridges
Publisher PD
Aging concrete structures: a review of mechanics and concepts
The safe and cost-efficient management of our built infrastructure is a challenging task considering the expected service life of at least 50 years. In spite of time-dependent changes in material properties, deterioration processes and changing demand by society, the structures need to satisfy many technical requirements related to serviceability, durability, sustainability and bearing capacity. This review paper summarizes the challenges associated with the safe design and maintenance of aging concrete structures and gives an overview of some concepts and approaches that are being developed to address these challenges
Synthetic rating system for railway bridge management
Railway bridges deteriorate with age. Factors such as environmental effects on different materials of a bridge, variation of loads, fatigue, etc will reduce the remaining life of bridges. Bridges are currently rated individually for maintenance and repair actions according to the structural conditions of their elements. Dealing with thousands of bridges and several factors that cause deterioration, makes the rating process extremely complicated. Current simplified but practical rating methods are not based on an accurate structural condition assessment system. On the other hand, the sophisticated but more accurate methods are only used for a single bridge or particular types of bridges. It is therefore necessary to develop a practical and accurate system which will be capable of rating a network of railway bridges. This paper introduces a new method for rating a network of bridges based on their current and future structural conditions. The method identifies typical bridges representing a group of railway bridges. The most crucial agents will be determined and categorized to criticality and vulnerability factors. Classification based on structural configuration, loading, and critical deterioration factors will be conducted. Finally a rating method for a network of railway bridges that takes into account the effects of damaged structural components due to variations in loading and environmental conditions on the integrity of the whole structure will be proposed. The outcome of this research is expected to significantly improve the rating methods for railway bridges by considering the unique characteristics of different factors and incorporating the correlation between them
Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology
INE/AUTC 10.0
Efficient design of post-tensioned concrete box-girder road bridges based on sustainable multi-objective criteria
[EN] Bridges, as an important component of infrastructure, are expected to meet all the requirements for a modern society. Traditionally, the primary aim in bridge design has been to achieve the lowest cost while guaranteeing the structural efficiency. However, concerns regarding building a more sustainable future have change the priorities of society. Ecological and durable structures are increasingly demanded. Under these premises, heuristic optimization methods provide an effective alternative to structural designs based on experience. The emergence of new materials, structural designs and sustainable criteria motivate the need to create a methodology for the automatic and accurate design of a real post-tensioned concrete bridge that considers all these aspects. For the first time, this thesis studies the efficient design of post-tensioned concrete box-girder road bridges from a sustainable point of view. This research integrates environmental, safety and durability criteria into the optimum design of the bridge. The methodology proposed provides multiple trade-off solutions that hardly increase the cost and achieve improved safety and durability. Likewise, this approach quantifies the sustainable criteria in economic terms, and evaluates the effect of these criteria on the best values of the variables.
In this context, a multi-objective optimization is formulated to provide multiple trade-off and high-performing solutions that balance economic, ecologic and societal goals. An optimization design program selects the best geometry, concrete type, reinforcement and post-tensioning steel that meet the objectives selected. A three-span continuous box-girder road bridge located in a coastal region is selected for a case study. This approach provides vital knowledge about this type of bridge in the sustainable context. The life-cycle perspective has been included through a lifetime performance evaluation that models the bridge deterioration process due to chloride-induced corrosion. The economic, environmental and societal impacts of maintenance actions required to extend the service life are examined. Therefore, the proposed goals for an efficient design have been switch from initial stage to life-cycle consideration.
Faced with the large computational time of multi-objective optimization and finite-element analysis, artificial neural networks (ANNs) are integrated in the proposed methodology. ANNs are trained to predict the structural response based on the design variables, without the need to analyze the bridge response. The multi-objective optimization problem results in a set of trade-off solutions characterized by the presence of conflicting objectives. The final selection of preferred solutions is simplified by a decision-making technique. A rational technique converts a verbal pairwise comparison between criteria with a degree of uncertainty into numerical values that guarantee the consistency of judgments. This thesis gives a guide for the sustainable design of concrete structures. The use of the proposed approach leads to designs with lower life-cycle cost and emissions compared to general design approaches. Both bridge safety and durability can be improved with a little cost increment by choosing the correct design variables. In addition, this methodology is applicable to any type of structure and material.[ES] Los puentes, como parte importante de una infraestructura, se espera que reĂşnan todos los requisitos de una sociedad moderna. Tradicionalmente, el objetivo principal en el diseĂąo de puentes ha sido lograr el menor coste mientras se garantiza la eficiencia estructural. Sin embargo, la preocupaciĂłn por construir un futuro mĂĄs sostenible ha provocado un cambio en las prioridades de la sociedad. Estructuras mĂĄs ecolĂłgicas y duraderas son cada vez mĂĄs demandadas. Bajo estas premisas, los mĂŠtodos de optimizaciĂłn heurĂstica proporcionan una alternativa eficaz a los diseĂąos estructurales basados en la experiencia. La apariciĂłn de nuevos materiales, diseĂąos estructurales y criterios sostenibles motivan la necesidad de crear una metodologĂa para el diseĂąo automĂĄtico y preciso de un puente real de hormigĂłn postesado que considere todos estos aspectos. Por primera vez, esta tesis estudia el diseĂąo eficiente de puentes de hormigĂłn postesado con secciĂłn en cajĂłn desde un punto de vista sostenible. Esta investigaciĂłn integra criterios ambientales, de seguridad estructural y durabilidad en el diseĂąo Ăłptimo del puente. La metodologĂa propuesta proporciona mĂşltiples soluciones que apenas encarecen el coste y mejoran la seguridad y durabilidad. Al mismo tiempo, se cuantifica el enfoque sostenible en tĂŠrminos econĂłmicos, y se evalĂşa el efecto que tienen dichos criterios en el valor Ăłptimo de las variables.
En este contexto, se formula una optimizaciĂłn multiobjetivo que proporciona soluciones eficientes y de compromiso entre los criterios econĂłmicos, ecolĂłgicos y sociales. Un programa de optimizaciĂłn del diseĂąo selecciona la mejor combinaciĂłn de geometrĂa, tipo de hormigĂłn, armadura y postesado que cumpla con los objetivos seleccionados. Se ha escogido como caso de estudio un puente continuo en cajĂłn de tres vanos situado en la costa. Este mĂŠtodo proporciona un mayor conocimiento sobre esta tipologĂa de puentes desde un punto de vista sostenible. Se ha estudiado el ciclo de vida a travĂŠs de la evaluaciĂłn del deterioro estructural del puente debido al ataque por cloruros. Se examina el impacto econĂłmico, ambiental y social que produce el mantenimiento necesario para extender la vida Ăştil del puente. Por lo tanto, los objetivos propuestos para un diseĂąo eficiente han sido trasladados desde la etapa inicial hasta la consideraciĂłn del ciclo de vida.
Para solucionar el problema del elevado tiempo de cĂĄlculo debido a la optimizaciĂłn multiobjetivo y el anĂĄlisis por elementos finitos, se han integrado redes neuronales en la metodologĂa propuesta. Las redes neuronales son entrenadas para predecir la respuesta estructural a partir de las variables de diseĂąo, sin la necesidad de analizar el puente. El problema de optimizaciĂłn multiobjetivo se traduce en un conjunto de soluciones de compromiso que representan objetivos contrapuestos. La selecciĂłn final de las soluciones preferidas se simplifica mediante una tĂŠcnica de toma de decisiones. Una tĂŠcnica estructurada convierte los juicios basados en comparaciones por pares de elementos con un grado de incertidumbre en valores numĂŠricos que garantizan la consistencia de dichos juicios. Esta tesis proporciona una guĂa que extiende y mejora las recomendaciones sobre el diseĂąo de estructuras de hormigĂłn dentro del contexto de desarrollo sostenible. El uso de la metodologĂa propuesta lleva a diseĂąos con menor coste y emisiones del ciclo de vida, comparado con diseĂąos que siguen metodologĂas generales. Los resultados demuestran que mediante una correcta elecciĂłn del valor de las variables se puede mejorar la seguridad y durabilidad del puente con un pequeĂąo incremento del coste. AdemĂĄs, esta metodologĂa es aplicable a cualquier tipo de estructura y material.[CA] Els ponts, com a part important d'una infraestructura, s'espera que reunisquen tots els requisits d'una societat moderna. Tradicionalment, l'objectiu principal en el disseny de ponts ha sigut aconseguir el menor cost mentres es garantix l'eficiència estructural. No obstant això, la preocupaciĂł per construir un futur mĂŠs sostenible ha provocat un canvi en les prioritats de la societat. Estructures mĂŠs ecològiques i durables sĂłn cada vegada mĂŠs demandades. Davall estes premisses, els mètodes d'optimitzaciĂł heurĂstica proporcionen una alternativa eficaç als dissenys estructurals basats en l'experiència. L'apariciĂł de nous materials, dissenys estructurals i criteris sostenibles motiven la necessitat de crear una metodologia per al disseny automĂ tic i precĂs d'un pont real de formigĂł posttesat que considere tots estos aspectos. Per primera vegada, esta tesi estudia el disseny eficient de ponts de formigĂł posttesat amb secciĂł en calaix des d'un punt de vista sostenible. Esta investigaciĂł integra criteris ambientals, de seguretat estructural i durabilitat en el disseny òptim del pont. La metodologia proposada proporciona mĂşltiples solucions que a penes encarixen el cost i milloren la seguretat i durabilitat. Al mateix temps, es quantifica l'enfocament sostenible en termes econòmics, i s'avalua l'efecte que tenen els dits criteris en el valor òptim de les variables.
En este context, es formula una optimitzaciĂł multiobjetivo que proporciona solucions eficients i de compromĂs entre els criteris econòmics, ecològics i socials. Un programa d'optimitzaciĂł del disseny selecciona la millor geometria, tipus de formigĂł, armadura i posttesat que complisquen amb els objectius seleccionats. S'ha triat com a cas d'estudi un pont continu en calaix de tres vans situat en la costa. Este mètode proporciona un major coneixement sobre esta tipologia de ponts des d'un punt de vista sostenible. S'ha estudiat el cicle de vida a travĂŠs de l'avaluaciĂł del deteriorament estructural del pont a causa de l'atac per clorurs. S'examina l'impacte econòmic, ambiental i social que produĂŻx el manteniment necessari per a estendre la vida Ăştil del pont. Per tant, els objectius proposats per a un disseny eficient han sigut traslladats des de l'etapa inicial fins a la consideraciĂł del cicle de vida.
Per a solucionar el problema de l'elevat temps de cĂ lcul degut a l'optimitzaciĂł multiobjetivo i l'anĂ lisi per elements finits, s'han integrat xarxes neuronals en la metodologia proposada. Les xarxes neuronals sĂłn entrenades per a predir la resposta estructural a partir de les variables de disseny, sense la necessitat d'analitzar el pont. El problema d'optimitzaciĂł multiobjetivo es traduĂŻx en un conjunt de solucions de compromĂs que representen objectius contraposats. La selecciĂł final de les solucions preferides se simplifica per mitjĂ d'una tècnica de presa de decisions. Una tècnica estructurada convertix els juĂs basats en comparacions per parells d'elements amb un grau d'incertesa en valors numèrics que garantixen la consistència dels dits juĂs. Esta tesi proporciona una guia que estĂŠn i millora les recomanacions sobre el disseny d'estructures de formigĂł dins del context de desenrotllament sostenible. L'Ăşs de la metodologia proposada porta a dissenys amb menor cost i emissions del cicle de vida, comparat amb dissenys que seguixen metodologies generals. Els resultats demostren que per mitjĂ d'una correcta elecciĂł del valor de les variables es pot millorar la seguretat i durabilitat del pont amb un xicotet increment del cost. A mĂŠs, esta metodologia ĂŠs aplicable a qualsevol tipus d'estructura i material.GarcĂa Segura, T. (2016). Efficient design of post-tensioned concrete box-girder road bridges based on sustainable multi-objective criteria [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/73147TESI
On systematic approaches for interpreted information transfer of inspection data from bridge models to structural analysis
In conjunction with the improved methods of monitoring damage and degradation processes, the interest in reliability assessment of reinforced concrete bridges is increasing in recent years. Automated imagebased inspections of the structural surface provide valuable data to extract quantitative information about deteriorations, such as crack patterns. However, the knowledge gain results from processing this information in a structural context, i.e. relating the damage artifacts to building components. This way, transformation to structural analysis is enabled. This approach sets two further requirements: availability of structural bridge information and a standardized storage for interoperability with subsequent analysis tools. Since the involved large datasets are only efficiently processed in an automated manner, the implementation of the complete workflow from damage and building data to structural analysis is targeted in this work. First, domain concepts are derived from the back-end tasks: structural analysis, damage modeling, and life-cycle assessment. The common interoperability format, the Industry Foundation Class (IFC), and processes in these domains are further assessed. The need for usercontrolled interpretation steps is identified and the developed prototype thus allows interaction at subsequent model stages. The latter has the advantage that interpretation steps can be individually separated into either a structural analysis or a damage information model or a combination of both. This approach to damage information processing from the perspective of structural analysis is then validated in different case studies
Safety Grade Evaluation of Aqueduct Structure Based on Fuzzy Cloud Theory Analysis
In view of the limitation of natural conversion between qualitative concept and quantitative value, the fuzzy analysis method cannot be employed to improve the multi-stage fuzzy evaluation method. Improvement of multilevel fuzzy evaluation method based on cloud theory was found, which could comprehensively consider the uncertainty of random combinations and the fuzziness of interaction between influencing factors, and the shortcomings of conventional fuzzy evaluation methods as well eliminated. The structure of 5#U-aqueduct in Jingdian Irrigation District (Gansu, China) was chosen as the research object. Based on the multi-level fuzzy evaluation index system of structural safety, experts were invited to score the importance of factors according to the cloud theory scale criterion to establish a judgment matrix. Therefore, the evaluation set, weight and membership cloud model of evaluation system was constituted by means of bridge safety assessment criterion and cloud generator principle. Furthermore, comprehensive evaluation results of aqueduct service states were obtained by multistage fuzzy composite mapping method, and the actual position of structural safety grade was obtained by comparing the evaluation result with the comment layer cloud drop diagram. The results showed that using cloud model parameters (Ex, En and He) to describe the relative importance of factors can better reflect the randomness and fuzziness of each other than the traditional single number, which was helpful to get the evaluation results accurately and objectively; The comprehensive evaluation results of the aqueduct structure obtained by calculation were WV(75.149, 9.95, 4.16).The simulated cloud droplet diagram was located between II and III classes, and tends to the III standard, which indicated that the overall security of the structure was sufferable. However, attention should be paid to the maintenance and repair of the detailed components. The consequences agreed with the evaluation results of the experts, which indicates that the improved evaluation method has good practicability as well as can be popularized and applied
Durability enhancement of half-joints in RC bridges through external prestressed tendons: The Musmeci Bridge's case study
This paper numerically investigates the effect of post-tension interventions to strengthen the deteriorated half-joints of the Musmeci Bridge in Potenza (Italy), with the primary objective of increasing the ultimate load-bearing capacity and monitoring the secondary effects in terms of preventing or limiting cracking patterns. Bearing this in mind, the study aims to investigate the role of the reinforcement detailing, of the post-tension stress and of the corroding time in the presence of chlorides, outlining the intervention ability to improve the structure's durability. To this end, nonlinear finite element models are provided with chloride ions diffusion analysis to investigate corrosion initiation and progress in reinforced concrete elements and account for deterioration due to two scenarios (45 and 95 years). Results show the significant impact of reinforcement layout as the presence of inclined bars increases the ultimate load by about 86 %. The ultimate load improvement is in the range 50â55 % when the intervention is carried out after 45 years while it is equal to about 30â35 % if a period of 95 years is last since the construction. This latter highlights the significant influence of the intervention timeliness on structural durability
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