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  • Diagnostic load testing and assessment of existing bridges: examples of application

     Olaszek, Piotr; Lagoda, Marek; Casas Rius, Joan Ramon
    Structure and infrastructure engineering
    Date of publication: 2014
    Journal article

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    Load testing method is a significant tool in the assessment of bridge safety. One type of load tests is diagnostic load testing, the aim of which is to establish a comparison between real bridge behaviour and analytical calculation. It can be used either as acceptance test of the structures or as an estimation tool for the load carrying capacity of the already existing structures that have been in service for some time. This article presents diagnostic load tests and three examples of their application to various bridge structures and emphasises their diagnostic potential for assessment. In the majority of cases of diagnostic load tests presented in the literature, the experimental results (deflections, strains, etc) are very close or lower than the predicted ones and for this reason, such tests are expected to validate the existing structure. However, in the cases presented here, it is shown how the experimental results differ considerably from the expected ones. Since the theoretical and the experimental results of all three examples did not match, it was highly recommended to keep the matter under close investigation. A deep insight into the bridges showed serviceability and safety concerns and in some cases a repair/strengthening was necessary.

  • Near-fault isolation of cable-stayed bridges using RNC isolator

     Ismail Abdelkareem Moustafa, Mohammed; Casas Rius, Joan Ramon; Rodellar Benede, Jose Julian
    Engineering structures
    Date of publication: 2013-11
    Journal article

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    This paper investigates the near-fault (NF) seismic performance of a recent isolation system, referred to as Roll-N-Cage (RNC) isolator, considering the cable-stayed Bill Emerson Memorial Bridge in Missouri, USA. Under NF ground motion, the seismic isolation devices might perform poorly because of large isolator displacements caused by long-period large velocity and displacement pulses associated with such strong motion. The RNC isolator is designed to achieve a balance in controlling isolator displacement demands and structural accelerations. It provides in a single unit all the necessary functions of rigid support, horizontal flexibility with enhanced stability and energy dissipation characteristics. Moreover, it is distinguished from other isolation devices by two unique features: (1) it has a built-in energy absorbing buffer to limit the isolated deck displacement under severe seismic excitations to a preset value and (2) it has a built-in linear recentering mechanism that prevents residual displacement after earthquakes. The seismic response of the RNC-isolated cable-stayed bridge is investigated using nonlinear time history analysis under three recorded NF earthquakes and three synthetic ground accelerations that capture many of the kinematic characteristics of recorded NF ground motions. The results show that the RNC isolator is a convenient isolation system in protecting cable-stayed bridges against NF earthquakes.

    This paper investigates the near-fault (NF) seismic performance of a recent isolation system, referred to as Roll-N-Cage (RNC) isolator, considering the cable-stayed Bill Emerson Memorial Bridge in Missouri, USA. Under NF ground motion, the seismic isolation devices might perform poorly because of large isolator displacements caused by long-period large velocity and displacement pulses associated with such strong motion. The RNC isolator is designed to achieve a balance in controlling isolator displacement demands and structural accelerations. It provides in a single unit all the necessary functions of rigid support, horizontal flexibility with enhanced stability and energy dissipation characteristics. Moreover, it is distinguished from other isolation devices by two unique features: (1) it has a built-in energy absorbing buffer to limit the isolated deck displacement under severe seismic excitations to a preset value and (2) it has a built-in linear recentering mechanism that prevents residual displacement after earthquakes. The seismic response of the RNC-isolated cable-stayed bridge is investigated using nonlinear time history analysis under three recorded NF earthquakes and three synthetic ground accelerations that capture many of the kinematic characteristics of recorded NF ground motions. The results show that the RNC isolator is a convenient isolation system in protecting cable-stayed bridges against NF earthquakes.

  • New structural joint by rebar looping applied to segmental bridge construction: fatigue strength tests

     Villalba Herrero, Sergio; Casas Rius, Joan Ramon; Aparicio Bengoechea, Angel Carlos; Villalba Herrero, Vicente
    ASCE. Journal of bridge engineering
    Date of publication: 2013-11
    Journal article

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    The objective of this research has been to design, develop, and evaluate experimentally a modified type of construction joint of limited length between concrete slab segments. The design concept is based on an anchorage hook of reduced development length stiffened by transverse reinforcement bars. The purpose of this paper is to investigate the mechanical behavior of the joint in terms of stiffness and strength for an application that requires high durability, which often leads to serviceability problems such as cracking and water leakage at transverse joints. This can regularly appear in bridges. Additionally, bridge decks are structures that are subjected to repeated loading such as traffic loads, making it necessary to evaluate the behavior of joints under fatigue load. Therefore, studies focusing on the strength, stiffness, and serviceability of the joints must be carried out. This paper investigates experimentally the fatigue behavior and strength of loop joints with regard to the loop bar diameter, loop joint width, and applied load ranges. These results were compared with the behavior of RC slabs without joints. A total of eight slabs were fabricated for fatigue loading tests, and the failures of the different specimens (with loop joints and without) were obtained. From the test results, the mechanical behavior of the slabs with loop joints was confirmed to be similar to that of the slabs without joints. The experimental loop joint design was found to perform correctly under fatigue loads.

  • Quantifying redundancy and robustness of structures

     Cavaco, E. S.; Casas Rius, Joan Ramon; Neves, L. A. C.
    Workshop on Safety, Failures and Robustness of Large Structures
    Presentation's date: 2013-02-15
    Presentation of work at congresses

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  • Structural behavior and design criteria for bridge strengthening by tied arch. Comparison with network arch bridges

     Valenzuela, Matías A.; Casas Rius, Joan Ramon
    International Conference on Arch Bridges
    Presentation's date: 2013-10-04
    Presentation of work at congresses

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    This study focuses on a new strengthening method of continuous bridges with several spans that present extensive damage in their foundation/piers due to scour and erosion. The method consists on the construction of a new upper steel arch with a network hanger's arrangement over the original deck with the aim to hang the existing deck to the new arch. The deck is acting as a tie in the new structural configuration. This allows to remove the damaged foundations/piers, deriving on an arch bridges with an span-length similar to the total length of the strengthened bridge and avoiding future problems related to scouring. The paper discusses about the resisting mechanisms that control the structural optimization process and therefore defines the design criteria. The main target of this process is different for each case, namely: the optimization of the arch in traditional network bridges; the limitation of maximum and minimum stresses in the deck in the case of strengthened bridges. Finally, it allows the comparison of each case, setting the differences between them and providing a new line of research on the topic of the tied arch method.

    This study focuses on a new strengthening method of continuous bridges with several spans that present extensive damage in their foundation/piers due to scour and erosion. The method consists on the construction of a new upper steel arch with a network hanger's arrangement over the original deck with the aim to hang the existing deck to the new arch. The deck is acting as a tie in the new structural configuration. This allows to remove the damaged foundations/piers, deriving on an arch bridges with an span-length similar to the total length of the strengthened bridge and avoiding future problems related to scouring. The paper discusses about the resisting mechanisms that control the structural optimization process and therefore defines the design criteria. The main target of this process is different for each case, namely: the optimization of the arch in traditional network bridges; the limitation of maximum and minimum stresses in the deck in the case of strengthened bridges. Finally, it allows the comparison of each case, setting the differences between them and providing a new line of research on the topic of the tied arch method.

  • Robustness of corroded reinforced concrete structures: a structural performance approach

     Cavaco, E. S.; Casas Rius, Joan Ramon; Neves, L. A. C.; Huespe, Alfredo Edmundo
    Structure and infrastructure engineering
    Date of publication: 2013
    Journal article

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  • Load rating of highway bridges by proof-loading

     Casas Rius, Joan Ramon; Gómez, Juan D.
    KSCE journal of civil engineering
    Date of publication: 2013-04
    Journal article

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  • Redundancy and robustness in the design and evaluation of bridges: European and North American perspectives

     Anitori, Giorgio; Casas Rius, Joan Ramon; Ghosn, Michel
    ASCE. Journal of bridge engineering
    Date of publication: 2013-12
    Journal article

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    In this paper, current and proposed methodologies for assessing the robustness and redundancy of bridge structures are discussed and an overview of the latest advances in research is presented along with proposals for implementation in bridge design and evaluation codes. In particular, European and North American standard codes and guidelines, including the Eurocode, AASHTO, and the Canadian Standards Association (CSA), as well as some national European codes and related guidelines, are compared. Research projects, including those of the European Cooperation of Science and Technology (COST) and the U.S. National Cooperative Highway Research Program (NCHRP), represent key links between research activities and the need for implementing concepts of structural redundancy and robustness into the codes. The activities undertaken by COST and NCHRP constitute attempts to synthetize, simplify, and implement theoretical concepts that have been discussed over many years. This review shows that the U.S. approach concentrates on developing tools and criteria for the numerical evaluation of the capability of a bridge structure to continue to carry load after the failure of a member, whereas the European approach, still in a more theoretical phase, lacks specific guidelines for bridges and uses available building recommendations. This paper also presents a critical assessment of the state of the art and argues that criteria implementable in future generations of bridge codes should be based on quantifiable measures of risk, which is a subject still in its very early stages of development.

  • Nuevo proceso constructivo de viaductos con cimbra autolanzable y nueva secuencia evolutiva

     Díaz De terán lópez, Jose Ramon
    Defense's date: 2013-09-12
    Universitat Politècnica de Catalunya
    Theses

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  • 2012 Outstanding Paper Award, Scientific Paper category

     Wisniewski, Dawid; Casas Rius, Joan Ramon; Ghosn, Michel
    Award or recognition

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  • Safety requirements and probabilistic models of resistance in the assessment of existing railway bridges

     Casas Rius, Joan Ramon; Wisniewski, Dawid
    Structure and infrastructure engineering
    Date of publication: 2013-06
    Journal article

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  • Application of optical fiber distributed sensing to health monitoring of concrete structures

     Villalba Herrero, Sergio; Casas Rius, Joan Ramon
    Mechanical systems and signal processing
    Date of publication: 2013-08
    Journal article

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    The use of Optical Backscatter Reflectometer (OBR) sensors is a promising measurement technology for Structural Health Monitoring (SHM) as it offers the possibility of continuous monitoring of strain and temperature along the fiber. Several applications to materials used in the aeronautical construction have demonstrated the feasibility of such technique. These materials (composites, steel, aluminum) apart from having a smooth surface where the bonding of the sensor is easily carried out, they also have a continuous strain field when subject to external loading and therefore the bonding of the OBR on the material surface is not in danger for high levels of loading as the OBR can easily follow the strain in the material. The application of such type of sensor to concrete structures may present some difficulties due to (1) the roughness of the concrete surface and the heterogeneity due to the presence of aggregates of several sizes, (2) the fact that reinforced concrete cracks at very low level of load, appearance of a discontinuity in the surface and the strain field that may provoke a break or debonding of the optical fiber. However the feasibility of using OBR in the SHM of civil engineering constructions made of concrete is also of great interest, mainly because in this type of structures it is impossible to know where the crack may appear and therefore severe cracking (dangerous for the structure operation) can appear without warning of the monitoring if sensors are not placed in the particular location where the crack appears. In order to explore the potentiality of detecting cracks as they appear without failure or debonding, as well as the compatibility of the OBR bonding to the concrete surfaces, this paper shows the test carried out in the loading up to failure of a concrete slab.

  • Fatigue-safety assessment of reinforced concrete (RC) bridges: application to the Brazilian highway network

     Rodrigues, J. Fernando; Casas Rius, Joan Ramon; ALFONSO DE OLIVEIRA ALMEIDA, PEDRO
    Structure and infrastructure engineering
    Date of publication: 2013-03
    Journal article

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  • Codes for safety assessment of existing bridges: current state and further development

     Wisniewski, Dawid; Casas Rius, Joan Ramon; Ghosn, Michel
    Structural engineering international
    Date of publication: 2012-11
    Journal article

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    During the past decade, new codes for the assessment of existing bridges have been developed in Canada, the USA, as well as the UK, Denmark, and Switzerland. The practical application of these codes proved to be successful as they allowed for keeping in operation many bridges that no longer met the design criteria but were otherwise able to safely carry the applied loads. Because of the success of the national codes, the possibility of developing a new Eurocode for Bridge Safety Assessment is under consideration. Building on the experience from the various national codes and recent research, a bridge assessment Eurocode should specifically include the following key elements: (a) the possibility of directly using probability-based methods, (b) the inclusion of structural system redundancy and robustness criteria, (c) the use of site-specific live loads and dynamic amplification factors, (d) the incorporation of field measurements and diagnostic test data, and (e) the consideration of proof load testing. The objective of this paper is to review how the above-listed key elements are addressed in existing assessment codes and recommend possible improvements to current evaluation methods to be considered in the development of the new assessment Eurocode for bridges.

  • Robustness assessment of a corroded RC bridge deck

     Cavaco, E. S.; Neves, L. A. C.; Casas Rius, Joan Ramon
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2012-07-09
    Presentation of work at congresses

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  • Redundancy of highway bridge decks

     Anitori, Giorgio; Casas Rius, Joan Ramon; Ghosn, Michel
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2012-07-09
    Presentation of work at congresses

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  • An attempt to the determination of the partial safety factor for SFRC members subjected to bending forces

     Camos Andreu, Carles; Casas Rius, Joan Ramon; Molins Borrell, Climent
    RILEM International Symposium on Fibre Reinforced Concrete
    Presentation's date: 2012-09-20
    Presentation of work at congresses

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    In the last few years, research on techniques that permit the reduction or even the complete elimination of structural bar reinforcements has been intensified. The addition of steel fibres to the concrete matrix is proven to be an effective way of covering the deficiencies in this material when subjected to tensile stress. However, there still exists uncertainty surrounding some of the basis of design of structural members in ultimate condition. A clear example is the partial safety factor applied to the tensile strength. In this paper, a reliability-based analysis is carried out through the study of a particular application, such as the tunnel lining concrete segments built in an experimental section of the L9 Metro tunnel in Barcelona, solely reinforced with steel fibres. Specimens were extracted from three different segments and tested in tension by using the Barcelona test. Such a representative sample of tensile strength results made possible an assessment of the degree of the existing safety in this particular case by applying the reliability method FORM. The reliability analysis suggested a partial factor equal to 1.77. This would represent a first step to obtain the general material safety factor, which may involve a calibration in a wide range of tunnel segments and afterwards, other structural members and applications of SFRC.

  • Application of OBR fiber optic technology in the structural health monitoring of the Can Fatjó viaduct (Cerdanyola del Vallé-Spain)

     Villalba Herrero, Vicente; Villalba Herrero, Sergio; Casas Rius, Joan Ramon
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2012-07-11
    Presentation of work at congresses

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  • Evaluation of bridge redundancy under lateral loads

     Anitori, Giorgio; Casas Rius, Joan Ramon; Ghosn, Michel
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2012-07-10
    Presentation of work at congresses

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  • Enhancement of bridge redundancy to lateral loads by FRP strengthening

     Anitori, Giorgio; Casas Rius, Joan Ramon; Ghosn, Michel; Jurado, S.
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2012-07-10
    Presentation of work at congresses

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  • Introduction: robustness

     Faber, Michael Havbro; Vrouwenvelder, Ton; Casas Rius, Joan Ramon; Høj, Niels Peter
    Structural engineering international
    Date of publication: 2012-02
    Journal article

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  • Improved procedure for equivalent linearization of bridges supported on hysteretic isolators

     Jara, M.; Jara, J. M.; Olmos, B.A.; Casas Rius, Joan Ramon
    Engineering structures
    Date of publication: 2012-02
    Journal article

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  • Efectos de los esfuerzos cortantes biaxiales en la respuesta sísmica de columnas de hormigón armado  Open access

     Osorio Bustamante, Edison
    Defense's date: 2012-12-14
    Department of Construction Engineering, Universitat Politècnica de Catalunya
    Theses

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    Durante un terremoto, las columnas de hormigón armado pueden verse sometidas a movimientos bidireccionales que pueden afectar su capacidad resistente y ductilidad. Sin embargo, las normas de diseño y evaluación sísmica no aportan recomendaciones explícitas para cuantificar el comportamiento de las columnas bajo dichas cargas. Esta investigación busca contribuir al análisis y cuantificación de los efectos de los esfuerzos cortantes biaxiales en la respuesta sísmica de columnas de hormigón armado. Con este objetivo, se realizó una recopilación del estado del conocimiento orientado a la revisión de los estudios experimentales y las estrategias de modelización numérica disponibles. De los estudios experimentales se concluyó que las columnas bajo cargas laterales bidireccionales ven reducida su capacidad resistente y ductilidad en comparación a las cargadas en una dirección. La deformación lateral del hormigón bajo cargas de compresión se ha estudiado pero no se encontró un modelo de su comportamiento bajo cargas cíclicas. En esta investigación, se estudió el comportamiento de la deformación lateral del hormigón mediante la ejecución de una primera campaña experimental en probetas cilíndricas de hormigón con cargas de compresión uniaxial cíclica. Con este estudio se aportaron curvas experimentales de tensión - deformación longitudinal y lateral con carga monótona y cíclica en hormigones de resistencia normal y alta. A partir de la interpretación de los datos experimentales, se propuso un modelo conceptual del comportamiento de la deformación lateral del hormigón. De forma paralela, se revisó y estudió el comportamiento de la deformación lateral del hormigón en un estado en compresión triaxial con base en resultados experimentales publicados en la literatura. Con las conclusiones de este estudio y el modelo conceptual en compresión uniaxial, se formuló un modelo analítico de la dilatancia del hormigón en compresión cíclica que se implementó en una ecuación constitutiva 3D. Los resultados se verificaron con los datos experimentales del hormigón en diferentes estados de compresión triaxial y diferentes materiales de confinamiento. Con la finalidad de alcanzar el objetivo general de la investigación, se diseñó, implementó y ejecutó una segunda campaña experimental en columnas con cargas unidireccionales y bidireccionales. Diez columnas circulares de hormigón armado se diseñaron y fabricaron con una disposición de armadura transversal insuficiente para que presentaran un nivel de ductilidad baja a media y un fallo por un mecanismo de cortante-flexión. Cuatro de estas columnas, fueron encamisadas con polímeros reforzados con fibras; dos con fibra de carbono (CFRP) y dos con fibra de aramida (AFRP). En los ensayos bajo carga bidireccional, la demanda de deformación en la armadura transversal fue mayor respecto al de carga unidireccional debido a que las deformaciones por esfuerzos cortantes y por la acción de confinamiento se acumulan. Las columnas con menor cuantía de armadura transversal y menor cuantía de FRP presentaron un incremento de la longitud de la rótula plástica. Dentro de esta investigación, se realizaron análisis de las columnas ensayadas con modelo seccional TINSA(Total-Interaction-Nonlinear-Section). El modelo seccional representa el decremento de resistencia y ductilidad y la mayor deformación de los cercos que se presentó en los experimentos con cargas bidireccionales. Por último, los efectos de los esfuerzos cortantes se analizaron a nivel material, seccional y de elemento. Se derivaron expresiones analíticas para considerar los efectos de los esfuerzos cortantes en el diagrama tensión-deformación del hormigón, la relación momento - curvatura y la longitud de la rótula plástica. Las expresiones analíticas encontradas se usaron en un modelo de análisis de rótula concentrada para obtener la curva de capacidad de la columna. Los resultados del modelo se corroboraron con los resultados experimentales de esta investigación.

    During an earthquake, reinforced concrete columns may be subjected to bi-directional displacements undermining their strength and ductility. However, the current codes for the seismic design and assessments of structures do not provide explicit provisions for the quantification of the effects of biaxial shear forces on the seismic response of reinforced concrete columns. This investigation is aimed at contributions to the analysis and quantification of the effects of biaxial shear forces on the seismic response of reinforced concrete columns. With this purpose, a state of the art review about the available experimental studies and numerical modeling strategies was performed. From the experimental studies, it is concluded that both the strength and ductility of the columns subjected to biaxial shear forces are reduced with respect to those subjected to uniaxial shear forces. The lateral deformation of concrete under compressive loads has been studied but has not formulated a model of its behavior under cyclic loading. In this research, a first experimental program on cylindrical concrete specimens subjected to cyclic compression was carried out in order to study the lateral deformation behavior. Experimental longitudinal stress- longitudinal and lateral strain curves, under monotonic and cyclic loading were provided, for normal and high strength concrete specimens. A conceptual model of the lateral behavior of concrete was proposed since interpretation of experimental data. Subsequently, the lateral behavior of concrete under a triaxial compression stress was reviewed and studied based on the experimental results available in the literature. Based on conclusions findings and using the conceptual model for uniaxial compression, an analytical model for the dilatancy of concrete under cyclic compression was formulated, which incorporate the above mentioned phenomena. The model was implemented into a 3D constitutive equation and their results were verified with experimental results under different triaxial stress states and different confinement materials. With the purpose of reaching the general objective of the investigation, a second experimental program on columns subjected to uniaxial and biaxial lateral forces and axial load was performed. Ten reinforced concrete circulars columns were designed and built, with an inadequate transverse reinforcement arrangement, providing insufficient ductility level so that a shear-flexure failure mechanism would take place. With the purpose of studying the behavior of strengthened columns under biaxial loading, four specimens were wrapped with carbon fiber reinforced polymers (FRP): two with carbon fiber (CFRP) and two with aramid fiber (AFRP). Under cyclic biaxial shear loading, the demand of strains in the transverse reinforcement was bigger than uniaxial loading because the strain by shear and the action of confinement were accumulated. The columns with smaller transverse reinforcement ratios and smaller FRP ratios showed increase of plastic hinge length. In this investigation, sectional analyses of the experimental behavior of the columns tested were performed with TINSA (Total-Interaction-Nonlinear-Section). The sectional model reproduces the decrement of strength and ductility as well as the greater strain in the hoops that was experimentally observed under biaxial tests. Finally, the effect of shear forces was analyzed at the material, section and structure levels. Analytical expressions were derived to consider the influence of the shear forces on the concrete stress-strain relationships, moment-curvature diagrams and on the plastic hinge length. The obtained analytical expressions were used in an analysis model of concentrated plastic hinges in order to obtain the capacity curve of the column. The model results were validated by comparing them satisfactorily with the experimental results presented in this investigation.

  • Caracterización estadística de los modelos de confinamiento y determinación de coeficientes parciales de seguridad para el refuerzo de pilas de puentes de hormigón mediante materiales compuestos (CFRP)  Open access

     Chambi Chuquichambi, José Luis
    Defense's date: 2012-11-30
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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    El continuo deterioro y/o daños causados en las estructuras de hormigón durante su vida útil, son fenómenos inevitables que conlleva el paso del tiempo y viene a ser un problema importante que ha conducido al desarrollo de nuevos materiales compuestos para el refuerzo estructural. En el caso de puentes, las situaciones en las que se hacen necesarias intervenciones de refuerzo pueden ser: estructuras afectadas por patologías inherentes a problemas de durabilidad, estructuras mal proyectadas y/o mal ejecutadas, estructuras que han sido dañadas por causas externas (impacto de vehículos, incendio, sismo, desastres naturales, etc.), estructuras afectadas por un cambio de uso o por un aumento de la carga de proyecto, o para soportar futuros sismos. Frente a ello, los métodos de refuerzo tradicional tales como el recrecido de hormigón, postensado exterior y refuerzo con chapas de acero, frecuentemente tienen desventajas inherentes como el incremento del peso de la estructura, la corrosión del acero y su elevado costo de manipulación y colocación. Ante estos inconvenientes, y más concretamente refiriéndonos al refuerzo de pilas de puentes, en años recientes se ha incrementado el uso de polímeros reforzados con fibra (FRP) como elemento de confinamiento de elementos de hormigón sometidos a compresión, debido a sus excelentes propiedades mecánicas y químicas, incrementando principalmente la resistencia y ductilidad de las pilas de hormigón. Sin embargo, su aplicación presenta aún lagunas que exigen seguir investigando aspectos como la falta de códigos y normas, la falta de experiencia en el comportamiento a largo plazo, la susceptibilidad al fuego, etc. Existen incertidumbres en las bases de cálculo durante el dimensionamiento de este refuerzo, una de ellas está precisamente en los coeficientes parciales de seguridad para el hormigón confinado que se deben adoptar en el diseño. Por ello, la presente tesis doctoral pretende aportar conocimientos en este campo, y más concretamente, definiendo dichos coeficientes parciales de seguridad para el hormigón confinado para el diseño del refuerzo de pilas de puentes de hormigón armado con polímeros reforzados con fibras de carbono (CFRP), mediante proceso de calibración basado en fiabilidad estructural. En ese sentido, primeramente, se ha recopilado toda la información bibliográfica disponible referida principalmente a dos aspectos: descripción de modelos de confinamiento para hormigón confinado con CFRP y datos de ensayos experimentales para la elaboración de una base de datos. Los modelos de confinamiento considerados en este estudio para elementos de hormigón de sección circular son de: Mander et al. 1988, Pilakoutas y Mortazavi 1997, Toutanji 1999, Spolestra y Monti 1999, Eid y Paultre 2008, Teng et al. 2009, Wu y Zhou 2010. Aplicando las expresiones de predicción de estos modelos a los datos experimentales recogidos en la base de datos, obtenemos como resultado tensiones y deformaciones últimas, y con ellos, mediante un análisis estadístico de valores teóricos respecto a valores experimentales para cada modelo de confinamiento, y, tras un análisis comparativo entre los diferentes modelos definimos el modelo que mejor ajuste presenta respecto a los datos experimentales (modelo de Teng et al. 2009). Para dicho modelo, se ha realizado la caracterización estadística. Puesto que es poco probable esperar que un formato de norma de diseño estructural pueda representar todas las situaciones de diseño, los sistemas estructurales y tipologías de pilas de puentes para los cuales se ha realizado la calibración en este estudio, son los puentes de tramo recto de varios vanos con pilas de hormigón armado tipo columnas circulares. Las pilas pueden estar formadas por un fuste único o bien por dos fustes. Esta tipología de tablero y de pila cubre la mayor parte de los puentes existentes en las actuales vías de comunicación. Para definir los coeficientes parciales de seguridad para el hormigón confinado γcc, se ha realizado la calibración basado en fiabilidad estructural, para un rango posible de soluciones de refuerzo con CFRP en las tipologías de pilas de puentes de los sistemas estructurales estudiados. Para ello, se tienen en cuenta las incertidumbres de las variables que intervienen, y mediante simulación se caracterizan estadísticamente las variables de resistencia y solicitación. Teniendo caracterizadas estas dos variables, según los niveles requeridos de seguridad estructural se determina la probabilidad de fallo o índice de fiabilidad para diferentes valores de γcc. Los coeficientes parciales de seguridad quedarán definidos para aquellas situaciones, tales que, los índices de fiabilidad calculados en las pilas reforzadas dimensionadas con dichos coeficientes, den valores iguales o superiores al índice de fiabilidad objetivo, que en este estudio se ha fijado en . Finalmente, la propuesta de coeficientes parciales de seguridad a utilizar es la siguiente: γcc = 1,15 para tmín ≤ t ≤ 2 mm γcc = 1,30 para t > 2mm

    The continuous deterioration and/or damages caused in the concrete structures during their lifetime, are unavoidable phenomena which the passage of time entails and gets to be an important problem that it has led to the development of new composite materials used for the structural reinforcement. The methods of traditional reinforcement such as concrete increased, prestressed exterior and the reinforcement with steel sheets, frequently they have inherent disadvantages like the increase of the weight of the structure, the corrosion of the steel and its high cost of manipulation and positioning. Given these disadvantages, and more specifically referring us to the reinforcement of pillars of bridges, in recent years the use of fibre reinforced polymers (FRP) has increased as an element of confinement. However, its use still still shows some gaps which demand to continue investigating some of their aspects such as the lack of codes and rules, the lack of experience in the long term behaviour, the susceptibility to the fire, etc. Uncertainties exist in the calculation bases along the dimensioning of this reinforcement, one of them precisely lays in the partial coefficients of safety for the confined concrete that must be to adopted in the design. For this purpose, the present doctoral thesis tries to contribute knowledge in this field, and more specifically, defining these partial coefficients of safety of the confined concrete for the design of the reinforcement of bridge pillars of reinforced concrete with carbon fibre reinforced polymers (CFRP), by means of calibration process based on structural reliability. In this sense, firstly, has been compiled all the bibliographical information available mainly referred to two aspects: description of confinement models for confined concrete with CFRP and data obtained from experimental tests for the elaboration of a data base. Applying the prediction expressions of confinement models to the experimental data collected in the data base, we obtain as a result the stresses and strains ultimate, and from them, by means of a statistical analysis of theoretical values in respect to experimental values for each single model of confinement, and, after a comparative analysis between the different models we define the model that beste adjustment presents with respect to the experimental data (model of Teng et al.). For this model, the statistical characterization has been performed. Since it is unlikely to expect that a structural design frame rule may represent all the situations of design, the structural systems and typologies of bridge pillars for which the calibration has been performed in this study, are the bridges of straight section with several spans with reinforced concrete pillars of the type of circular columns. The pillars can be formed by a only fust or by two fusts. This typology of roadway and pillar covers most of the existing bridges in the current communication routes. In order to define the partial coefficients of safety for the confined concrete ¿cc, the calibration has been performed based on structural reliability, for a possible range of solutions of reinforcement with CFRP in the typologies of bridges pillars of the studied structural systems. For such a purpose, the uncertainties related of the variables which intervene have been taken into consideration, and by means of simulation the variables of strength and stress have been statistically characterized. Once these two variables have been characterized, according to the required levels of structural safety the probability of failure or reliability index for different values of ¿cc has been determined. The partial coefficients of safety will be defined for those situations, such that, the reliability indexes calculated in the reinforced pillars dimensioned with such coefficients, give results equal or higher than the objective reliability index, which has been established in ß=3,5 in this study.

    La contínua deterioració i/o danys causats en les estructures de formigó durant la seva vida útil, són fenòmens inevitables que comporta el pas del temps i es convertix en un problema important que ha conduït al desenvolupament de nous materials composts per al reforç estructural. En el cas de ponts, les situacions en les quals es fan necessàries intervencions de reforç poden ser: estructures afectades per patologies inherents a problemes de durabilitat, estructures mal projectades i/o mal executades, estructures que han estat danyades per causes externes (impacte de vehicles, incendi, sisme, desastres naturals, etc.), estructures afectades per un canvi d'ús o per un augment de la càrrega de projecte, o per suportar futurs sismes. Davant tot això, els mètodes de reforç tradicional tals com el recrescut de formigó, post tensat exterior i reforç amb xapes d'acer, freqüentment tenen desavantatges inherents com ara el increment del pes de l'estructura, la corrosió de l'acer i el seu elevat cost de manipulació i col·locació. Davant aquests inconvenients, i més concretament fent esment al reforç de pilars de ponts, en anys recents s'ha incrementat l'ús de polímers reforçats amb fibra (FRP) com a element de confinament d'elements de formigó sotmesos a compressió, a causa de les seves excel·lents propietats mecàniques i químiques, incrementant principalment la resistència i ductilitat de les pilars de formigó. No obstant això, la seva aplicació presenta encara punts foscos que exigeixen seguir investigant aspectes com la falta de codis i normes, la falta d'experiència en el comportament a llarg termini, la susceptibilitat al foc, etc. Existeixen incerteses a les bases de càlcul durant el dimensionament d'aquest reforç, una d'elles està precisament en els coeficients parcials de seguretat per al formigó confinat que s'han d'adoptar en el disseny. Per això, la present tesi doctoral pretén aportar coneixements en aquest camp, i més concretament, definint aquests coeficients parcials de seguretat per al formigó confinat per al disseny del reforç de pilars de ponts de formigó armat amb polímers reforçats amb fibres de carboni (CFRP), mitjançant procés de calibratge basat en fiabilitat estructural. En aquest sentit, primerament, s'han recopilat tota la informació bibliogràfica disponible referida principalment a dos aspectes: descripció de models de confinament per a formigó confinat amb CFRP i dades d'assajos experimentals per a l'elaboració d'una base de dades. Els models de confinament considerats en aquest estudi per a elements de formigó de secció circular són de: Mander et al. 1988, Pilakoutas i Mortazavi 1997, Toutanji 1999, Spolestra i Monti 1999, Eid i Paultre 2008, Teng et al. 2009, Wu i Zhou 2010. Aplicant les expressions de predicció d'aquests models a les dades experimentals recollides en la base de dades, obtenim com resultat tensions i deformacions últimes, i amb ells, mitjançant una anàlisi estadística de valors teòrics respecte a valors experimentals per a cada model de confinament, i, després d'una anàlisi comparativa entre els diferents models definim el model que millor ajust presenta respecte a les dades experimentals (model de Teng et al. 2009). Per a aquest model, s'ha realitzat la caracterització estadística. Ates que és poc probable esperar que un format de norma de disseny estructural pugui representar totes les situacions de disseny, els sistemes estructurals i tipologies de pilars de ponts pels quals s'ha realitzat el calibratge en aquest estudi, són els ponts de tram recte de diverses obertures amb pilars de formigó armat tipus columnes circulars. Les pilars poden estar formades per un fust únic o bé per dos fustos. Aquesta tipologia de tauler i de pilar cobreix la major part dels ponts existents en les actuals vies de comunicació. Per tal de definir els coeficients parcials de seguretat per al formigó confinat γcc, s'ha realitzat el calibratge basat en fiabilitat estructural, per a un rang possible de solucions de reforç amb CFRP en les tipologies de pilars de ponts dels sistemes estructurals estudiats. Per a això, es tenen en compte les incerteses de les variables que intervenen, i mitjançant simulació es caracteritzen estadísticament les variables de resistència i sol·licitació. Tenint caracteritzades aquestes dues variables, segons els nivells requerits de seguretat estructural es determina la probabilitat de fallada o índex de fiabilitat per a diferents valors de γcc. Els coeficients parcials de seguretat quedaran definits, per a aquelles situacions, tals que, els índexs de fiabilitat calculats en les pilars reforçades dimensionadas amb aquests coeficients donin valors iguals o superiors a l'índex de fiabilitat objectiu, que en aquest estudi s'ha fixat en β = 3,5. Finalment, la proposta de coeficients parcials de seguretat a utilitzar és la següent: γcc = 1,15 per a tmín ≤ t ≤ 2 mm

  • Refuerzo de puentes de luces medias por conversión en arco atirantado tipo network  Open access

     Valenzuela Saavedra, Matías Andrés
    Defense's date: 2012-03-23
    Department of Construction Engineering, Universitat Politècnica de Catalunya
    Theses

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    Según estudios estadísticos a nivel mundial, una de las principales causas de fallos en puentes corresponde a problemas relacionados con la interacción entre estructura e hidráulica produciendo altos costos humanos y económicos. La mayoría de las patologías se relacionan con procesos de socavación y erosión en pilas y estribos, específicamente en las cimentaciones de las pilas, siendo necesario tomar medidas para su refuerzo. Las dificultades en la inspección y mantenimiento de la infraestructura, junto con la ineficiencia y elevados costos en la implementación de los refuerzos convencionales (pilotajes, recrecidos, entre otros) ha motivado al Departamento de Puentes, Ministerio de Obras Públicas de Chile, el desarrollo de una nueva técnica de refuerzo con el objetivo de eliminar la causa de la patología: las pilas y sus cimentaciones, focalizándose el estudio en puentes con tipología de viga continua de varios vanos de hormigón armado. La metodología propuesta considera el cambio estructural del puente incorporando arcos superiores atirantados con configuración de péndolas network y vertical encargados de levantar tablero y esfuerzos en el arco. A partir de ello, se verifica el comportamiento del refuerzo en etapas de construcción y posteriormente en estado de servicio mediante un análisis de las cargas de tráfico y accidentales (capítulo 5). Los resultados dan lugar a la sistematización del método de refuerzo alternativo propuesto, incluyendo la propuesta estructural y tecnológica, la factibilidad del proceso constructivo y, finalmente, un conjunto de criterios básicos de diseño para este tipo de refuerzos (capítulo 6). Finalmente, la validación estructural del método y un primer estudio económico de costes comparado respecto a otros métodos convencionales de refuerzo, entregan para futuros ingenieros un conjunto de criterios y recomendaciones básicas para la implementación de esta técnica. el tablero del puente original, el cuál, gracias a la aplicación de un pretensado exterior, actúa como tirante del sistema del arco, contrarrestando los empujes horizontales del mismo en los arranques. El levantamiento del tablero desde los soportes permite la demolición de éstos, reduciendo los riesgos relacionados con la interacción de la estructura con el flujo del cauce; además de reutilizar parte del puente original y entregar un nuevo concepto estético. Para determinar la factibilidad del método, se pone énfasis en el estudio del método constructivo a partir del proceso de tesado de las péndolas así como en su comportamiento en servicio posterior, teniendo en cuenta las solicitaciones sísmicas, de gran importancia en Chile. El proceso constructivo a plantear debe satisfacer dos requisitos fundamentales: evitar tensiones excesivas en el tablero para no superar las solicitaciones existentes en el puente original; y permitir un levantamiento total de la superestructura desde las pilas dañadas. El tener que mantener unos determinados niveles de tensión en el tablero original supone una complejidad adicional respecto a lo que sería el diseño y construcción de un puente arco tipo network totalmente nuevo. Nos encontramos pues ante un problema de optimización (orden y magnitud de las fuerzas de tesado para levantar el tablero) con fuertes condiciones de contorno (no superar los niveles máximos de esfuerzos en el tablero original). Frente a la complejidad del proceso de optimización multiobjetivo del proceso de tesado, se descarta el uso de una optimización manual (prueba y error), en favor de una metodología que combina el uso automatizado de programas de elementos finitos y métodos de optimización meta-heurísticos (algoritmos genéticos). Esta herramienta, desarrollada, calibrada y validada (capítulo 3), proporciona todo un conjunto de soluciones factibles del proceso constructivo. El algoritmo desarrollado se utiliza como herramienta para el estudio e implementación de esta metodología en dos puentes carreteros ubicados en la zona central de Chile, con tipología original de viga continua y con importantes problemas de socavación: San Luis (60 metros de longitud total distribuidos en cuatro vanos) y Puangue (72 metros de longitud total distribuidos en cuatro vanos). Mediante la aplicación práctica a estos dos puentes carreteros, se desarrolla un estudio paramétrico en etapa constructiva (capítulo 4), considerando como variables: el tipo de perfil del arco, la configuración de las péndolas network, entre otros, entregándose la influencia que tiene cada una de ellas en relación a la capacidad de levantamiento, admisibilidad de tensiones en el

    According to statistical studies worldwide, one of the main causes of damages in bridges correspond to problems related to the interaction between structure and hydraulic provoking high human and economic costs. Most pathology is related to processes of scour and erosion in piers and abutments, specifically in the foundations of the piers, being necessary to take strengthening measures. The difficulties in inspection and maintenance of infrastructure, and the inefficiency related to the high costs in the implementation of conventional strengthening methods (pile driving, screeds, etc.) has prompted the Department of Bridges, Ministry of Public Works of Chile, the development of a new method of strengthening in order to eliminate the cause of the pathology: the piers and its foundations, focusing the study on continuous bridges with several spans and cross-section of built up reinforced concrete beams plus an upper slab. The proposed methodology considers a structural change of bridge by the incorporation of upper arches with a network and vertical hangers arrangement, which, through the application of external prestressing, allows the system to behave as a bow tied, balancing the horizontal thrusts in its edges. The lifting of the deck from the supports via the vertical hangers allows their demolition, reducing the risks associated with the interaction of the structure with the river flow (scour), in addition to reuse the original bridge and deliver a new aesthetic. To determine the feasibility of the method, the study emphasizes on the construction method, specially on the process of tensioning of the hangers and their behaviour in service, considering the seismic loads, relevant in Chile. The construction process proposed must satisfy two fundamental requirements: to avoid excessive stress on the deck not to exceed the stresses existing in the original bridge or the maximum material strength and allowing a total lift of the superstructure from the damaged piers. Maintain certain level of stress on the original deck is an additional significant complexity, compared with the design and construction of a new network arch bridge. This derives on an optimization problem (order and magnitude of tensioning forces to lift the deck) with strong boundary conditions (not to exceed the maximum internal forces in the original deck). Given the complexity of multi-objective optimization of the tensioning process, the use of manual optimization (trial and error) is rejected, for a methodology that combines the use of automated finite element programs and methods of optimization meta-heuristics (genetic algorithms). This tool, developed, calibrated and validated (Chapter 3) provides a whole set of feasible solutions of the construction process. The algorithm developed is used as a tool for the study and implementation of this methodology on two highway bridges located in central Chile, with a original typology of continuous beam and important problems of scour: San Luis (60 meters total length in four spans) and Puangue (72 meters total length in four spans). Through the practical application of these two road bridges, a parametric study of the constructive stages is developed (Chapter 4), considering as variables: the arch profile, the network hangers arrangement, among others, giving the influence of each in relation to the lifting capacity, admissibility of stresses in the deck and internal forces in the arch. From this, the performance in construction and service stages is studied through an analysis of traffic and accidental loads (chapter 5). The results, lead to the systematization of the strengthening proposed method, including structural and technological proposals, the feasibility of the construction process and finally, a set of basic design criteria for this type of strengthening (Chapter 6). Finally, the structural validation of the method and a first economic study of costs compared to other conventional strengthening methods give a set of criteria and recommendations for the implementation of this technique.

    Segons estudis estadístics a nivell mundial, una de les principals causes de fallades en ponts correspon a problemes relacionats amb la interacció entre estructura i hidràulica produint alts costos humans i econòmics. La majoria de les patologies es relacionen amb processos de soscavació i erosió en piles i estreps, específicament en les fonamentacions de les piles, i caldrà prendre mesures per reforç. Les dificultats en la inspecció i manteniment de la infraestructura, juntament amb la ineficiència i elevats costos en la implementació dels reforços convencionals (pilotatges, recrescuts, entre altres) ha motivat al Departament de Ponts, Ministeri d'Obres Públiques de Xile, el desenvolupament de una nova tècnica de reforç amb l'objectiu d'eliminar la causa de la patologia: les piles i els seus fonaments, focalitzant l'estudi en ponts amb tipologia de biga contínua de diversos trams de formigó armat. La metodologia proposada considera el canvi estructural del pont incorporant arcs superiors atirantats amb configuració de pèndoles network i vertical encarregats d'aixecar el tauler del pont original, el qual, gràcies a l'aplicació d'un pretensat exterior, actua com tirant del sistema de l'arc, contrarestant les empentes horitzontals de la mateixa en les arrencades. L'aixecament del tauler des dels supports permet la demolició d'aquests, reduint els riscos relacionats amb la interacció de l'estructura amb el flux de la llera, a més de reutilitzar part del pont original i donar un nou concepte estètic. Per determinar la factibilitat del mètode, es posa èmfasi en l'estudi del mètode constructiu a partir del procés de tesat de les pèndoles així com en el seu comportament en servei posterior, tenint en compte les sol·licitacions sísmiques, de gran importància a Xile. El procés constructiu a plantejar ha de satisfer dos requisits fonamentals: evitar tensions excessives en el tauler per no superar les sol·licitacions existents en el pont original, i permetre un aixecament total de la superestructura des de les piles danyades. El haver de mantenir uns determinats nivells de tensió en el tauler original suposa una complexitat addicional respecte al que seria el disseny i construcció d'un pont arc tipus network totalment nou. Ens trobem doncs davant d'un problema d'optimització (ordre i magnitud de les forces de tesat per aixecar el tauler) amb fortes condicions de contorn (no superar els nivells màxims d'esforços en el tauler original). Davant la complexitat del procés d'optimització multiobjectiu del procés de tesat, es descarta l'ús d'una optimització manual (prova i error), a favor d'una metodologia que combina l'ús automatitzat de programes d'elements finits i mètodes d'optimització meta-heurístics (algorismes genètics). Aquesta eina, desenvolupada, calibrada i validada (capítol 3), proporciona tot un conjunt de solucions factibles del procés constructiu. El algorisme desenvolupat s'utilitza com a eina per a l'estudi i implementació d'aquesta metodologia en dos ponts carreters ubicats a la zona central de Xile, amb tipologia original de biga contínua i amb importants problemes de soscavació: Sant Lluís (60 metres de longitud total distribuïts en quatre obertures) i Puangue (72 metres de longitud total distribuïts en quatre obertures). Mitjançant l'aplicació pràctica a aquests dos ponts carreters, es desenvolupa un estudi paramètric en etapa constructiva (capítol 4), considerant com a variables: el tipus de perfil del arc, la configuració de les pèndoles network, entre altres, lliurant la influència que té cada una d'elles en relació a la capacitat d'aixecament, admissibilitat de tensions en el tauler i esforços en l'arc. A partir d'això, es verifica el comportament del reforç en etapes de construcció i posteriorment en estat de servei mitjançant una anàlisi de les càrregues de trànsit i accidentals (capítol 5). Els resultats donen lloc a la sistematització del mètode de reforç alternatiu proposat, inclosa la proposta estructural i tecnològica, la factibilitat del procés constructiu i, finalment, un conjunt de criteris bàsics de disseny per a aquest tipus de reforços (capítol 6). Finalment, la validació estructural del mètode i un primer estudi econòmic de costos comparat respecte a altres mètodes convencionals de reforç, lliuren per a futurs enginyers un conjunt de criteris i recomanacions bàsiques per a la implementació d'aquesta tècnica.

  • Verificación experimental de uniones mediante lazos de armadura y su aplicación en la construcción evolutiva de puentes  Open access

     Contreras Lopez, Catalina Del Pilar
    Defense's date: 2012-03-23
    Department of Construction Engineering, Universitat Politècnica de Catalunya
    Theses

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    The box-girder is currently the solution for large prestressed concrete bridges, being most used today in steel and mixed structures. Their widespread use is due to the strength characteristics and versatility, using various construction processes depending on the conditions of the work. However, it has the great disadvantage that the concrete should be done in phases. Because of the advantages of this section is really important develop new techniques to improve the performance, and reduce construction times. The construction of the top slab involves extension straight joints. It has been observed that this kind of joint requires additional measures during execution, either from the point of view of the danger to operators or remove the inside formwork. As a result, it is needed propose a new type of joint, by loops, reducing risks, minimizing the construction times and making easier the work on site. To understand the behaviour of a structure with this loop joint, are built concrete sections with representative dimensions of a railway bridge, with a concrete joint, reproducing, as far as possible, what happens in reality. These sections will be tested experimentally. In a previous study has been analysed the performance in a simple bending test. For this reason, in this study is checked the response in pure bending. Dynamic and static campaigns are done, using for this a total of 8 slabs, existing three types of union based on European codes: - Reference Slab (LR) with a continuous reinforcement - DIN Slab (LD) with a loop joint according to DIN 1045 - Experimental Slab (LE) with the proposed loop joint With these results it is possible to know the performance until failure, under static and dynamics loads with a number of cycles of 2 x 10^6. In static load campaign are tested 3 slabs, representatives of the different types of continuity. With these results is possible to make a comparison between the behaviour of the slabs associated with: longitudinal and transverse strain, deflections and concrete joint opening. In dynamic load campaign are tested 5 slabs, three of them with the same type of reinforcement and the other two representatives of the others types. In each of these tests are applied different load ranges, depending on the objectives, defining 5 tests: 1. LR: ¿s=150 MPa --> Q_max=141 kN y Q_min=50 kN 2. LD: ¿s=150 MPa --> Q_max=141 kN y Q_min=50 kN 3. LE_2: ¿s=150 MPa --> Q_max=141 kN y Q_min=50 kN 4. LE_3: ¿s=150 MPa --> Q_max=210 kN y Q_min=119 kN 5. LE_4: ¿s=127 MPa --> Q_max=125 kN y Q_min=47 kN Based on the test load levels, are made comparisons between these results and the results obtained for an experimental slab under simple bending (L.F.S.), associated to: dynamic deflection, concrete joint opening, longitudinal and transverse strain, and failure loads after finished dynamic tests. Finally, are proposed futures research works, in order to increase the knowledge associated with a loop joint reinforcement under another type of efforts.

  • Bridge strengthening by network arch: structural performance and design criteria

     Valenzuela, Matías A.; Casas Rius, Joan Ramon
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2012-07-09
    Presentation of work at congresses

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  • IABMAS senior Prize

     Casas Rius, Joan Ramon
    Award or recognition

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  • Statistical analysis of existing models for flexural strengthening of concrete bridge beams using FRP sheets

     Ceci, Alfredo; Casas Rius, Joan Ramon; Ghosn, Michel
    Construction & building materials
    Date of publication: 2012-02
    Journal article

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  • Monitoring, modelling and assessment of structural deterioration in marine environments

     Casas Rius, Joan Ramon; O'Connor, Alan
    Structure and infrastructure engineering
    Date of publication: 2012-06
    Journal article

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  • Verificación experimental de uniones mediante lazos de armadura y su aplicación en la construcción evolutiva de puentes

     Contreras, Catalina P.; Casas Rius, Joan Ramon; Aparicio Bengoechea, Angel Carlos
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-26
    Presentation of work at congresses

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    El presente trabajo entrega un estudio a partir de ensayos de un nuevo tipo de empalme para puentes de sección cajón construidos evolutivamente, buscando reducir riesgos asociados a la construcción y plazos de ejecución. Por esta razón se realizan ensayos de rotura en losetas de hormigón armado, estableciendo una comparación de resultados para el empalme experimental con otras losetas de armadura continua y empalme mediante lazos establecido en DIN 1045. Se entregan los resultados de carga de rotura, deformaciones en la armadura, flechas y abertura de junta de hormigonado para un ensayo de flexión pura. Se plantean las metodologías de ensayo y se entrega un primer ensayo a fatiga, esperando concluir en futuros trabajos acerca del comportamiento frente a este fenómeno en las diferentes losetas.

  • Diseño y validación experimental de uniones mediante superposición con lazos en viaductos de hormigón de sección transversal evolutiva

     Villalba Herrero, Sergio; Aparicio Bengoechea, Angel Carlos; Casas Rius, Joan Ramon
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-26
    Presentation of work at congresses

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    En este trabajo se estudia el diseño y la posterior validación experimental de una unión estructural de longitud limitada, basada en la superposición a través de lazos de armaduras yuxtapuestas, confinadas en su interior mediante armadura transversal, para materializar el enlace de dos elementos estructurales ejecutados en distintas fases de hormigonado. En la presente investigación se analiza la respuesta y el comportamiento frente a flexión simple de 16 losas de hormigón armado, cuya totalidad, engloban dos campañas experimentales, una primera frente a carga estática, seguida de una segunda frente a carga cíclica. Los parámetros de longitud total del lazo proyectado y del diámetro empleado son analizados y comparados frente a la capacidad última resistente. Asimismo, los valores obtenidos son cotejados con los obtenidos mediante las losas de referencia (sin dispositivo de unión) para validar su aplicabilidad.

  • Refuerzo de puentes por cambio de esquema estructural: optimización mediante algoritmo genético

     Valenzuela, Matías A.; Casas Rius, Joan Ramon
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-26
    Presentation of work at congresses

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    La presente comunicación entrega un estudio detallado del proceso constructivo y de tesado para el refuerzo de puentes con tipología longitudinal de vigas continuas convirtiéndolos en puentes en arco atirantado (tipo network). Se presentan las etapas básicas propuestas en aspectos de construcción, se establecen las hipótesis del estudio de tesado e implementa el método de tesado a partir de la optimización automatizada mediante algoritmos genéticos, definiendo criterios como: variables de diseño, restricciones y funciones objetivo. Finalmente se presenta un ejemplo aplicado al puente San Luis en Chile, ilustrando el uso del algoritmo.

  • Reliability and redundancy of bridge systems under lateral loads

     Anitori, G.; Casas Rius, Joan Ramon; Ghosn, Michel
    ASCE Structures Congress
    Presentation's date: 2011-04-15
    Presentation of work at congresses

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    A methodology is proposed to analyze the structural redundancy of bridge systems under lateral loads. The paper compares the results obtained from a probabilistic approach to those of a simplified deterministic analysis. A non-linear finite element analysis based on a 3-D frame model is performed for an example bridge considered to be representative of the behavior of structures with integral column-superstructure connections. The analysis accounts for material non-linearity using realistic models for the stress-strain relationships of the different constituents. The quantification of the available redundancy levels is evaluated using reliability as well as deterministic criteria previously proposed in NCHRP 458.

  • Monitorización y salud estructural: aplicación de la fibra óptica distribuida (OBR) en estructuras de hormigón

     Villalba Herrero, Sergio; Casas Rius, Joan Ramon
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-25
    Presentation of work at congresses

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  • A reliability-based measure of robustness for concrete structures subjected to corrosion

     Cavaco, E. S.; Neves, L. A. C.; Casas Rius, Joan Ramon
    International Conference on Applications of Statistics and Probability in Civil Engineering
    Presentation's date: 2011-08-02
    Presentation of work at congresses

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  • Robustness analysis of deteriorating reinforced concrete slabs

     Cavaco, E. S.; Neves, L. A. C.; Gonçalves, Rui; Casas Rius, Joan Ramon
    International Conference on Space Structures
    Presentation's date: 2011-09-21
    Presentation of work at congresses

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    Corrosion of reinforcement bars in concrete structures is the most significant deterioration mechanism in these structures. Corrosion is extremely difficult to predict and, consequently, can be regarded as an unpredictable event. Following this, robustness assessment methods can be employed to define the susceptibility of a structure to corrosion. In this paper a strategy to evaluate the impact of corrosion on the robustness of reinforced concrete structures is presented. To assess robustness the index proposed by Cavaco et al. [1] is adopted. This index, Rd , is defined based on an average of the structure reliability variation with corrosion. To calculate the reliability index of the corroded structure, a nonlinear analysis of the cross section, coupled with a First Order Reliability Method (FORM) analysis, is performed. To predict bond strength deterioration the M-Pull model proposed by [2] is considered. Results show that structure reliability is significantly affected by reinforcement corrosion. The most important factor causing load capacity decreasing is bond strength deterioration. Independently of the reinforcement ratio the residual reliability tends to a lower bound, corresponding to the resistance of the unreinforced concrete section. At this stage no adhesion exists between steel and concrete. The susceptibility of different design solutions is compared in terms of the robustness indicator, Rd, showing that, although less reinforced structure reveals a lower safety level, they are more robust since that safety level is less affected by corrosion.

  • Refuerzo de puentes con CFRP y estudio de su influencia sobre la redundancia frente a acciones horizontales

     Anitori, Giorgio; Jurado, S.; Chambi Chuquichambi, José Luis; Casas Rius, Joan Ramon; Ghosn, Michel
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2011-07-06
    Presentation of work at congresses

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  • Experimental verification of construction joints by reinforcement loops

     Contreras, Catalina P.; Aparicio Bengoechea, Angel Carlos; Casas Rius, Joan Ramon
    International Conference on Space Structures
    Presentation's date: 2011-09-21
    Presentation of work at congresses

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    The present work delivers one experimental study of a new type of joint reinforcement for boxgirder bridges constructed evolutionarily, seeking to reduce execution time, improve formwork placement inside the box section, and minimize work risks. For this reason, failure tests are carried out in reinforced concrete slabs, comparing the experimental results of proposed joint with continuous reinforcement and a loop union according to DIN 1045. The results are delivered in terms of resistance, deflection and concrete joint opening for a pure bending test. They are also included the results of a fatigue test, waiting to conclude in the next future the work about the behaviour of different concrete slabs.

  • Safety factors in the strengthening to flexure with CFRP of concrete bridges

     Casas Rius, Joan Ramon; Ghosn, Michel; Ceci, Alfredo
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2011-07-05
    Presentation of work at congresses

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  • Bridge strengthening by structural change: optimization via genetic algorithm

     Valenzuela, Matías A.; Casas Rius, Joan Ramon
    International Conference on Space Structures
    Presentation's date: 2011-09-20
    Presentation of work at congresses

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    This paper presents a detailed study of the construction and cable-stressing process for the strengthening of bridges by the conversion of the structural typology from continuous beams to tied-arch bridges. The basic stages of the construction method and the basic assumptions of the study and applications of stress method, based on automated optimization using genetic algorithms, are described. Additionally, a criterion of design variables, constraints and objective functions are defined. Finally, an example of application to the San Luis Bridge in Chile is presented and illustrates the use of the algorithm.

  • Vibration based criteria for damage control in bridge structures

     Rodrigues, J. Fernando; ALFONSO DE OLIVEIRA ALMEIDA, PEDRO; Casas Rius, Joan Ramon
    International Conference on Space Structures
    Presentation's date: 2011-09-22
    Presentation of work at congresses

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  • Monitorización continua-gestión estructural: monitorización del viaducto de la carretera BP-1413 (Cerdanyola del Vallés)

     Villalba Herrero, Vicente; Casas Rius, Joan Ramon
    Congreso de la Asociación Científico-Técnica del Hormigón Estructural
    Presentation's date: 2011-10-27
    Presentation of work at congresses

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    Se presenta la aplicación en un viaducto de un sistema de monitorización continúo (en el espacio y tiempo) de fibra óptica (OBR) que suministra datos a tiempo real para poder controlar y conocer el estado/comportamiento de la estructura. Se confirma la viabilidad del pegado de los 100m de fibra óptica sobre la superficie de hormigón y la lectura continua durante el periodo de investigación. Se obtienen lecturas de deformación y se comparan con las obtenidas en las pruebas de carga realizadas, confirmando la precisión de la tecnología (+-1 με). Gracias a esta precisión y a una resolución espacial de 10 με, el sistema propuesto aporta ventajas importantes respecto a otros equipos de monitorización de fibra óptica. La medición continua de deformaciones a lo largo de toda la longitud de la fibra permite además obtener las flechas. Se presentan los resultados obtenidos de la monitorización a tiempo real, como también futuras aplicaciones del sistema en otras obras de ingeniería civil y edificación.

  • Fibrous materials reinforced composites for structural health monitoring

     Güemes, Alfredo; Casas Rius, Joan Ramon
    Date of publication: 2011-04
    Book chapter

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    Structural Health Monitoring is becoming more and more used in civil engineering infrastructure. The technology for implementing SHM applications is presented in this Chapter. Details on instrumented civil constructions are then discussed, together with most innovative future trends.

  • Aplicación de criterios de robustez estructural para la ampliación de la vida útil de puentes existentes

     Aparicio Bengoechea, Angel Carlos; Ramos Schneider, Gonzalo; Valenzuela Saavedra, Andrés; Chambi Chuquichambi, José Luis; Casas Rius, Joan Ramon
    Participation in a competitive project

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  • Access to the full text
    Reliability-based assessment of masonry arch bridges  Open access

     Casas Rius, Joan Ramon
    Construction & building materials
    Date of publication: 2011-04
    Journal article

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    The paper presents a methodology for the probabilistic assessment of masonry arches at the serviceability and ultimate limit states. First, it explains the definition of the different failure modes and corresponding limit state functions that may occur depending on the type of masonry construction (single-ring and multi-ring). The most reported modes of failure are the four-hinge mechanism, the ring separation in multiring arches and the slippage at the foundations. Because of the lack of reliable material data (in the statistic sense) or available response models, only those more prone to be analyzed using reliability-based methods are shown in this paper: four-hinge mechanism and ring separation. The possibility of fatigue failure of masonry arch bridges under service loads and the proposal of reliability-based assessment methods at the ultimate level of the 4 hingemechanism are also analyzed. Finally, the proposed methodology is applied to an existing bridge.

    Postprint (author’s final draft)

  • Bridge strengthening by structural change: from continuous beam to network arch

     Valenzuela, M.; Casas Rius, Joan Ramon
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2010-07-13
    Presentation of work at congresses

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    In Chimbarongo, VI region of Chile, is located the San Luis road bridge, built in the year 1930. During last inspections have been detected severe scour in the piers, besides other damages, which have forced the closure of the structure. The strengthening done is through pile-driving. This system supposes a high technical complexity with significant intervention in the structure. In addition, there are new conditions of flow of pure waters that must bear the bridge. All these boundaries and requirements makes possible to study an alternative to this first strengthening proposal through an exchange of the structural typology of the bridge. The main objective of this study is to generate and evaluate this alternative strengthening proposal, consisting on the elimination of the piers of the bridge and later construction of a tied arch, in such a way to modify the structural behavior of the bridge, converting the original deck in the bottom tie of an upper arch and avoiding, in this way, any problem related to the foundation of the piers.

  • Target proof load factors for highway bridge assessment in Central and Eastern European Countries (CEEC)

     Gomez, Juan David; Casas Rius, Joan Ramon
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2010-07-13
    Presentation of work at congresses

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    As a part of the task of the EC 6th Framework Programme European Project ARCHES (Assessment and Rehabilitation of Central European Highway Structures), the paper proposes a simple method to obtain the target proof load that guarantees a required safety level on the bridge against the actual traffic. The proof load factors are obtained by means of a reliability-based calibration with 3 different safety levels. In this way, the bridge evaluator can choose the safety level to have in the bridge that has passed the proof load test. The calibration uses the traffic data obtained recently in 4 CEEC (Poland, Slovakia, Slovenia and the Czech Republic) with Weigh in Motion (WIM) techniques. The final result is a simple procedure based on charts and tables that a bridge evaluator without specific knowledge of reliability theory can easily apply.

  • Assessment and monitoring of existing bridges to avoid unnecessary strengthening or replacement

     Casas Rius, Joan Ramon
    International Conference on Bridge Maintenance, Safety and Management
    Presentation's date: 2010-07-13
    Presentation of work at congresses

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    The increasing volume of European transport urgently requires an effective road and rail system in Central European and Eastern countries (CEEC) with a major investment in building new and assessing and rehabilitating old structures. To decrease the number of bridges in CEEE to be strengthened or replaced due to lack of maintenance or increase of the trucks weight, it is essential to assess accurately their remaining capacity. It becomes important to develop more appropriate tools and procedures to avoid unnecessary interventions in bridges. Load testing carried out on bridges through years indicates that often bridges resist load in ways not always considered in the design or in the present bridge rating procedures. Therefore, substantial benefits can be realized if the bridges can be evaluated and rated based on non-destructive load tests and if the actual traffic loads can be well monitored as well, including their dynamic effect or dynamic allowance.