The accuracy of bridge system safety evaluations and reliability assessments obtained through refined structural analysis procedures depends on the proper modeling of traffic load effects. While the live-load models specified in AASHTO procedures were calibrated for use in combination with approximate analysis methods and load-distribution factors commonly used in the United States, these existing models may not produce accurate results when used in association with advanced finite-element analyses of bridge structures. This paper proposes a procedure for calibrating appropriate live-load models that can be used for advanced analyses of multigirder bridges. The calibration procedure is demonstrated using actual truck data collected at a representative set of weigh-in-motion (WIM) stations in New York State. Extreme value theory was used to project traffic-load effects to different service periods. The results are presented as live-load models developed for a 5-year typical rating interval and for a 75-year design life. The outcome of the calibration indicates that maximum traffic-load effects can be calculated using finite-element models with the help of a single truck for short to medium one-lane multigirder bridges and two side-by-side truck configurations for multilane bridges. The proposed analysis trucks have axle configurations of the standard AASHTO 3-S2 and Type 3 legal rating trucks with appropriate factors to amplify their nominal weights. The amplification factors reflected the presence of overweight trucks in the traffic stream and the probability of multiple presence. The proposed live-load models are readily implementable for deterministic refined analyses of highway bridges and for evaluating the reliability of bridges at ultimate limit states considering the system’s behavior.
López, R.; Pujadas, P.; Pialarissi Cavalaro, S.H.; Aguado, A. Construction & building materials Vol. 153, p. 835-845 DOI: 10.1016/j.conbuildmat.2017.07.136 Data de publicació: 2017-10 Article en revista
A bonded concrete overlay consists of a concrete layer poured over a deteriorated pavement. Its mechanical performance depends on the quality of the bond between the lower and the uppermost layers. This paper reports an extensive experimental program to evaluate bond strength between Conventional Concrete (CC) and Asphalt Concrete (AC) substrates and Self-Compacting High-Performance Concrete (SCHPC) overlays. In all, 8 interface treatments are tested under Direct Tension, pure shear “LCB”, and compressive Slant Shear tests. The results show that direct pouring of the SCHPC overlay over CC and AC substrates produces similar or higher strengths than the other treatments analyzed.
A día de hoy, los pavimentos de hormigón son una de las soluciones tradicionales para la construcción de firmes de carreteras y autopistas. Además, su uso también está ampliamente extendido en otro tipo de infraestructuras de transporte terrestre (calles, aceras o aeropuertos) así como en pavimentos industriales (almacenes o áreas de producción) y aparcamientos. Las ventajas medioambientales, tecnológicas y económicas que presentan sobre los pavimentos flexibles, junto al aumento de las inversiones en infraestructuras, hacen que a nivel mundial exista una tendencia creciente en la construcción de este tipo de pavimentos. A pesar de ello y aún con el nivel de desarrollo tecnológico actual, el desempeño de los pavimentos de hormigón puede ser no satisfactorio si su diseño y construcción no son adecuados. Basándose en las características del pavimento, su desempeño puede dividirse en dos etapas: tempranas edades (generalmente hasta los 28 días) y vida útil de servicio. Mientras que se han desarrollado muchos estudios y modelos para evaluar su vida útil, no ocurre lo mismo con el análisis a tempranas edades.En este contexto, en las últimas dos décadas el interés de la industria por el comportamiento a edades tempranas ha aumentado. Durante esta primera etapa pueden aparecer problemas relacionados con el comportamiento térmico, higrométrico y mecánico del hormigón. Por lo general y debido a la complejidad de los fenómenos que se produce, éstos se abordan únicamente de forma individual en la literatura. Sin embargo, con el fin de evaluar el comportamiento del material y su estructura a primeras edades, estos factores deben ser considerados conjuntamente.Los aspectos abordados en esta tesis doctoral comprenden el comportamiento a primeras edades del hormigón y la modelización de pavimentos de hormigón durante este periodo. El primer tema abarca la caracterización de las propiedades térmicas, higrométricas y mecánicas y su influencia global en el comportamiento del hormigón en edades tempranas. Varios de los factores que influyen en estos fenómenos son analizados y sintetizados por separado. El trabajo realizado muestra la posibilidad de integrar los fenómenos involucrados en el comportamiento a tempranas edades y cómo éste puede ser predicho un único modelo acoplado.El segundo tema presenta la aplicación del modelo desarrollado a los pavimentos de hormigón. Se desarrolla un estudio paramétrico en base a una serie de factores que se han encontrado tener una influencia significante en la fisuración del hormigón en edades tempranas. Se han derivado valores óptimos para parámetros físicos tales como la separación y el tiempo de corte de las juntas de los pavimentos. Los resultados numéricos muestran consistencia con la literatura.
Casas, J.; Matos, J. International Conference BESTInfra: Building up Efficient and Sustainable Transport Infrastructure p. 1-10 DOI: 10.1088/1757-899X/236/1/012051 Data de presentació: 2017-09-22 Presentació treball a congrés
In Europe, as all over the world, the need to manage roadway bridges in an efficientway led to the development of different management systems. Hence, nowadays, many European countries have their own system. Although they present a similar architectural framework, several differences can be appointed. These differences constitute a divergent mechanism that may conduct to different decisions on maintenance actions. Within the roadway bridge management process, the identification of maintenance needs is more effective when developed in a uniform and repeatable manner. This process can be accomplished by the identification of performance indicators and definition of performance goals and key performance indicators (KPI), improving the planning of maintenance strategies. Therefore, a discussion at a European level, seeking to achieve a standardized approach in this subject, will bring significant benefits. Accordingly, a COST Action is under way in Europe with the aim of standardizing the establishment of quality control plans for roadway bridges.
The Temple of Sagrada Familia presents singularities in terms of both the original design by architect Antoni Gaudí and the duration
of the construction, which started more than 120 years ago. In fact, its design was conceived before the development of reinforced concrete. Therefore, the construction materials and processes have evolved to adapt new technologies without compromising the vision of Gaudí. This willingness to maintain the original designs has obliged the technicians to resolve details that were not defined in the project, including the issue of how to cast elements at great heights and with a high amount of reinforcement. In this context, the possibility of using self-compacting concrete (SCC) emerged. This paper describes the different experiences in the Temple of Sagrada Familia with SCC, from requirements that led to using this material to the design of the mixes and the casting of the elements in situ.
Over the years, there have been numerous efforts by researchers in quantifying structural degradation and damage from vibration measurements. Traditionally, damage detection techniques in bridges have focused on the use of modal-based damage indicators, such as frequencies, mode shapes and mode shape derivatives. However, these parameters have been shown to be sensitive to environmental and operational variations and can be difficult to accurately extract under low-level ambient excitation. Recent research has found a correlation between certain vibration parameters, such as vibration intensity, and a group of damage bridges, suggesting that vibration parameters may detect damage if extracted correctly. The present study furthers these findings by examining a number of vibration parameters as damage indicators to discern their sensitivity to various condition states of a progressively damaged bridge under ambient excitation.
In this work, an experiment on two small concrete beams is described where Rayleigh based distributed optical fiber sensors (DOFS) are implemented together with traditional electrical strain gauges for the monitoring of these elements during a three-point load test. Part of the DOF sensor is embedded without protective coating directly in the rebar inside the concrete, being the remaining fiber glued to the surface of the element after the concrete hardening. This allows the direct comparison between the developed strains on the surface of concrete and the rebar with the use of a single sensor. Moreover, two types of adhesives are studied and then compared. From all the possible distributed sensing techniques, the Rayleigh based Optical Frequency Domain Reflectometer (OFDR) is the one which enables the better spatial resolution without the need of post-processing algorithms. In this way, in this experiment, this is going to be the used sensing technique.
Pujadas, P.; Blanco, A.; Pialarissi Cavalaro, S.H.; de la Fuente, A.; Aguado, A. Construction & building materials Vol. 149, num. 15, p. 790-800 DOI: 10.1016/j.conbuildmat.2017.05.166 Data de publicació: 2017-09 Article en revista
The flexural creep of plastic fiber reinforced concrete (PFRC) is a controversial issue since significant doubts regarding the suitability of this type of fiber and its influence in the long-term behavior of the material still exist. The objective of this paper is to evaluate the post-cracking creep response of PFRC beams under flexural load in comparison with that of steel fiber reinforced concrete (SFRC) beams. The aim is to explore how the pre-crack opening and the environmental condition affect the long term behavior of each material and identify differences. An experimental program was conducted with 30 concrete beams with dimension of 150 × 150 × 600 mm reinforced with plastic or steel fibers subjected to a 4-point bending creep test for 5 months under 2 environmental conditions. Results showed that the flexural creep coefficient of PFRC is 2 times bigger than that of SFRC. Despite that, the use of plastic fibers as reinforcement should not be rejected as long as the additional creep is considered in the design and the crack widths are limited to reduce the risk of tertiary creep.
Blanco, A.; Aire, C.; Pujadas, P.; Pialarissi Cavalaro, S.H. Construction & building materials Vol. 149, p. 207-217 DOI: 10.1016/j.conbuildmat.2017.05.135 Data de publicació: 2017-09 Article en revista
The behavior of concrete subjected to shear can be significantly improved by the addition of fibers, which may partially or totally substitute the traditional steel stirrups (also known as links). Design recommendations include formulations to account for the contribution of the fibers. However, these formulations take the results of small-scale bending tests as input parameters. The main reason for that is the lack of standardized tests and the difficulty to assess direct shear in fiber reinforced concrete (FRC) both for the design and for the quality control. The present study proposes a test for the characterization of the post-cracking shear response of FRC. The test is validated through an experimental program with conventional concrete and FRC. The influence of different parameters (geometry of the specimen, the type and the content of fiber) is assessed and a comparison is made between the push-off test and the one proposed here. Results of an in-depth statistical analysis indicate that the latter is a simpler and valid alternative to evaluate the post-cracking shear response of FRC.
Road asset management is a task of great responsibility, since it involves vital assets to the community. An efficient transportation network is essential for the modern society from the economic, societal and environmental point of view. Today, it is a challenge for operators to manage road infrastructures under their responsibility in an efficient way, meeting the present and future needs of the community they serve. For this purpose, authorities need to produce an asset management plan which should not only define the goals to be achieved by exploiting the roadway bridge network, but that should also identify the investment needs and priorities based on a life cycle cost criteria. In addition, a proper condition assessment of these assets must be conducted to support the decision-making process regarding their preservation.
En esta tesis doctoral se presenta el uso de un reflectómetro óptico de retrodispersión denominado sistema OBR (optical backscattered reflectometer por sus siglas en inglés), como una herramienta de monitorización de la salud estructural (MSE) en estructuras de hormigón, las cuales pueden presentar fisuras incluso en condiciones de servicio.La principal característica del sistema OBR es su gran sensibilidad y alta resolución espacial a través del uso de un cable de fibra óptica como sensor y que se denomina sensor de fibra óptica distribuida (SFOD). Lo anterior, produce registros de deformación en los cuales se puede identificar y localizar la presencia de fisuras. Así, en primer lugar se retoma la experiencia de una aplicación anterior, y se propone un método del cálculo de ancho de fisura promedio en estructuras de hormigón sujetas básicamente a flexión, y que se basa en la información de los registros de deformación que se obtienen con el sistema OBR. A continuación, el sistema OBR se aplica en el estudio de tres vigas de hormigón parcialmente pretensado (HPP) de 8 m de longitud y sujetas a esfuerzo cortante. Estas vigas fueron instrumentadas tanto en forma convencional con sensores discretos, como con un SFOD adherido a la superficie. Con base en los resultados experimentales obtenidos, se evalúa la capacidad del sistema OBR para monitorizar estructuras de hormigón sujetas a cortante, y se propone un método para detectar, localizar y posteriormente cuantificar el ancho de fisura promedio a cortante.Posteriormente, una de las tres vigas ensayadas a cortante y ya con la presencia de fisuras a lo largo de toda su longitud, es ensaya a flexión. En esta viga se evalúa la capacidad del sistema para detectar la presencia de fisuras ya existentes, y la aparición de nuevas fisuras. Una vez detectadas y localizadas las principales fisuras por flexión, se aplica el método del cálculo del ancho de fisura propuesto y se evalúan sus resultados. También se lleva a cabo la aplicación del sistema OBR de una estructura en condiciones reales. Lo anterior consistió en la monitorización a lo largo de casi ocho meses, del proceso ampliación de un puente de hormigón pretensado de aproximadamente 86 m de longitud. En esta aplicación, los efectos de temperatura, fueron un factor muy importante y se tuvo en cuenta su corrección para una interpretación correcta de los datos obtenidos. Por último, con base en lo observado a través de la información obtenida en cada uno de los ensayos experimentales comentados, se establecen las conclusiones en torno a las ventajas e inconvenientes de este tipo de sistemas opto-electrónicos de medición basados en el uso de SFOD, Cabe decir que la metodología propuesta en esta tesis produce unos resultados muy satisfactorios tanto en la detección, localización como cuantificación de la fisuración por flexión y cortante en estructuras de hormigón para niveles de solicitación de servicio.
The objective of this paper is to evaluate the influence of sulfate exposure on the pore network development of several Portland cement matrices. MIP, XRD and SEM analysis were performed at different ages in samples exposed to sulfates after 2 days of casting. Results suggest that patterns of precipitation of the expansive products are linked to the degree of refinement of the pore network. During early stages of exposure, large pores concentrate a higher proportion of the expansive product formed. At later stages, precipitation evolves towards finer pore sizes.
Wind farms are both a renewable energy production alternative and a profitable economic enterprise. At the same time these groups of wind towers can be a social-friendly solution if they solve challenging demands from the society such as integration in landscape, aesthetics, low noise nuisances…
This paper presents part of a complete research project that was carried out between 2009 and 2015. First this article presents a new wind tower proposal that has been designed to reduce these social impacts as well as satisfying environmental aspects, economic requirements and boundary conditions such as height, turbine power, soil conditions. This proposal is composed of precast concrete modules joined with high-resistance steel bars that define a post-tension structure. These components define an attractive and transparent tripod that is transversally reinforced with steel profiles. This system holds the Spanish patent “Support structure to wind turbines, number ES 2 319 709 B8” and aims to build 100-120m high towers. At this height there is better wind quality and large turbines of 3 MW can be installed.
Second, a sustainability assessment of this new hybrid wind tower has been carried out in order to evaluate its social, environmental and economic impacts compared to other solutions. Steel lattice structures, steel tubular systems, in situ concrete towers and precast concrete structures are the alternatives for wind farms that have been considered. MIVES, a MCDM methodology based on the value function concepts has been used to do this assessment, which has relied upon seminars of experts. This sustainability assessment enabled the identification of the aspects with the lowest sustainability index. These are the maintenance and deconstruction costs and for occupational hazards. Now these weak points can be corrected in the process of bringing the patented technology to market.
Lozano-Galant, J.A.; Lei, J.; Ramos, G.; Nogal, M.; Xu, D.; Turmo, J. Congreso de la Asociación Científico-Técnica del Hormigón Estructural p. 1-10 Data de presentació: 2017-06-22 Presentació treball a congrés
Torralba, V.; García-fontanet, A.; Plana, D.; Pérez, D.; Ramos, G.; Arranz, T.; Ainchil, J. Congreso de la Asociación Científico-Técnica del Hormigón Estructural p. 1-10 Data de presentació: 2017-06-21 Presentació treball a congrés
The use of Life Cycle Cost (LCC) tools in civil engineering is increasing, due to the need of infrastructure owners and operators to guarantee their assets maximum performance with an optimized budget. By considering these tools it will be possible to manage assets along their lifetime in a more sustainable and efficient way. Due to this reason, it was recently constituted a Task Group on fib to deal with existing LCC tools for concrete infrastructures. This paper gives an introduction to these tools, with a special emphasis to the added-value of LCC, and to the main contents of the fib TG 8.4 state-of-art technical report. This covers a description of existing LCC standards and guidelines, their applicability, the definition of different cost elements, the incorporation of risk in the analysis, etc.
The size effect is a well-known phenomenon in the design of reinforced
concrete structures. Although it has been studied extensively for conventional
concrete with or without traditional reinforcement, its influence on the
post-cracking behaviour of fibre-reinforced composites is scarcely reported in
literature. This is particularly true in the case of high performance
fibre-reinforced concrete (HPFRC), which allows the design of very thin elements
and whose behaviour may be highly influenced by their size. The aim of
this research was to evaluate the influence of the size of HPFRC beams on the
mechanical performance at a cross-sectional level. An experimental program
involving three-point bending tests of HPFRC on beams of dimensions
40 40 160, 100 100 400 and 150 150 600 mm was conducted.
Three steel fibre contents were investigated: 90, 140 and 190 kg/m3
bending tests were also simulated via a sectional analysis model, taking as a
reference the constitutive law described in the fib Model Code for Concrete
Structures 2010. The results suggest that the values of stress in the constitutive
model should depend upon the cross-sectional size of the beam. This is reflected
when adjusting the parameters of the MC2010 to fit the experimental values,
resulting in a coefficient of determination above 0.88 when comparing the ratio
between these two parameters and the size of the cross section.
de la Fuente, A.; Bairan, J.M.; Pialarissi Cavalaro, S.H.; Goodier, C.; Palmeri, A. fib Symposium p. 1530-1537 DOI: 10.1007/978-3-319-59471-2_176 Data de presentació: 2017-06-12 Presentació treball a congrés
Improvements in concrete technology, reinforcing systems and manufacturing processes enable the use of increasingly long reinforced precast concrete girders, contributing to the competitiveness of girders in concrete in comparison with other alternatives. The weight of the girders should be limited however, in order to achieve an optimum between span length and lifting and transportations costs. The current tendency in design is to minimize the width of the flanges, thus the girder becoming more flexible laterally and more prone to suffer instability phenomena during transient loading situations. An increasing number of accidents and damages associated with this instability problem are reported in the technical literature (e.g., Hurff 2010; Rose 2013). The main objective of this study is to describe a real case of lateral instability of a long prestressed concrete bridge girder during lifting as well asto perform a parametric study to understand the limits of the problem observed. Special attention is paid to the evaluation of the provisions gathered in the Model Code 2010 (MC - 2010) regarding the lateral stability, since these might not be sufficient to cover limit cases.
The use of fibre reinforced concrete (FRC) to produce segmental linings of TBM-constructed tunnels is an increasing tendency. So far, more than 50 tunnels have been constructed with this structural material, in some of these even using solely fibres as reinforcement. Moreover, several design guidelines (e.g., fib Model Code 2010) already include the FRC as structural material. There also exist specific guidelines for the design of FRC precast segment linings (e.g., ITAtech Report/7-15 and ACI 544.7R-16). These guidelines deal with the design of FRC considering the traditional limit state safety format. Therefore, partial safety factors for both the loads (¿L) and material strengths (¿M) must be considered. In particular, the magnitude of ¿M considered for compressive and tensile FRC strengths are assumed to be the same. Nonetheless, this assumption can be unrealistic, particularly in terms of flexural residual strength (fR) since this property present higher scatter than the compressive strength (fc). This is particularly true for elements with a reduced cracking surface (e.g., beams) due to the higher impact that uncertainties like fibre orientation and distribution have on the variability of fR. Therefore, this assumption can lead to lower reliability indexes (ß) than those established for traditional reinforced concrete structures. However, this variability tends to decrease with the increase of the width of the cracked sections (e.g., slabs). The results of a structural reliability analysis carried out to calibrate partial safety factors for fR is presented. Full-scale bending tests on precast segments with different dimensions, amounts and type of fibers were considered. This partial safety factors could be used in the design of future precast FRC tunnel linings.
During the process of structural system identification, errors are unavoidable. This paper analyzes the effects of measurement and simulation errors in structural system identification based on observability techniques. To illustrate the symbolic approach of this method a simply supported beam is analyzed step-by-step. This analysis provides, for the very first time in the literature, the parametric equations of the estimated parameters. The effects of several factors, such as errors in a particular measurement or in the whole measurement set, load location, measurement location or sign of the errors, on the accuracy of the identification results are also investigated. It is found that error in a particular measurement increases the errors of individual estimations, and this effect can be significantly mitigated by introducing random errors in the whole measurement set. The propagation of simulation errors when using observability techniques is illustrated by two structures with different measurement sets and loading cases. A fluctuation of the observed parameters around the real values is proved to be a characteristic of this method. Also, it is suggested that a sufficient combination of different load cases should be utilized to avoid the inaccurate estimation at the location of low curvature zones.
The assessment of bridge condition from vibration measurements has generally been determined via the monitoring of modal parameters determined though adaptations of the standard Fast Fourier Transform (FFT) or other stationary time-series based transformations. However, the nonstationary nature of measured vibration signals from damaged structures can limit the quality of frequency content information estimated by such methods. The Hilbert–Huang Transform’s (HHT) ability to decompose non-stationary measured vibration data into a time-frequency-energy representation allows signal variations to be identified sooner than other stationary-based transformations, thus potentially
allowing early detection of damage. The present study uses data obtained from a progressive damage test conducted on a real bridge subjected to excitation from a double axle passing vehicle as a test subject.
Decomposed vibration signals from the HHT and associated marginal spectrums are assessed to determine
structural condition for various damage states and different locations along the bridge.
In the past decade, several works and studies have been performed with the goal of improving the knowledge and developing new techniques associated with the application of Distributed Optical Fiber Sensors (DOFS) in order to widen the range of applications of these sensors and also to obtain more correct and reliable data. In this document, after a very brief introduction to the fundamentals of this technology, the most representative work being developed at UPC—BarcelonaTech with the use of these sensors is going to be described. These applications range from laboratory experiments to real world structures monitoring scenarios where different challenges and particular issues had to be overthrown in each one of them. Furthermore, the most recent laboratory experiment performed by this group where DOFS were deployed is going to be described in greater detail.
Durante la construcción de los puentes de hormigón, los fenómenos
diferidos, tales como la fluencia y la retracción, pueden afectar significativamente la geometría y los esfuerzos de este tipo de estructuras. De hecho, estos fenómenos modificarán la fuerza del tesado de los tirantes en fase de servicio. Para compensar estas pérdidas pueden ser necesarias operaciones de retesado, con el consiguiente incremento del coste de explotación. En la literatura se han presentado un gran número de métodos para simular el proceso constructivo de los puentes atirantados. Todos estos métodos suelen asegurar que no se exceden los esfuerzos ni las deformaciones admisibles en los diferentes elementos. Sin embargo, algunos de estos métodos, concretamente aquellos basados en una simulación “hacia atrás”, no permiten incluir directamente los efectos de la retracción ni la fluencia. Para recrear los efectos de estos fenómenos diferidos se suele utilizar una simulación “hacia delante”. El principal problema de esta simulación es que tradicionalmente incluye complejos procesos iterativos que incrementan el coste computacional. Para resolver estos problemas, en este artículo se propone un algoritmo, Forward-Direct Algorithm, que permite simular el proceso constructivo de los puentes atirantados de hormigón incluyendo los fenómenos de retracción y fluencia. La principal ventaja de este método es que permite compensar las pérdidas de los tirantes a lo largo de la vida útil de la estructura por medio de las operaciones de tesado realizadas durante el proceso constructivo, permitiendo así evitar las operaciones de retesado en servicio. Para ilustrar la simulación de este método, se analiza una estructura basada en un puente real.
Tradicionalmente, el comportamiento de las estructuras se suele modelizar mediante modelos numéricos con propiedades mecánicas conocidas. Sin embargo, los valores reales de las estructuras construidas raramente coinciden con los teóricos y para garantizar la fiabilidad del modelo es necesaria su calibración. A este proceso se le conoce como identificación estructural. En este artículo se presenta la aplicación de la observabilidad, para estimar el valor las rigideces
de estructuras reales a partir de su respuesta estática. Este método permite resolver el sistema de ecuaciones polinomiales que aparece cuando se consideran rigideces desconocidas dentro de la matriz de rigidez de una estructura.
Even if solid circular columns are very popular, codes do not usually propose specific formulations for evaluating the shear strength of such structural types or if they do, they do so in a very simplified manner. Despite the fact that shear stresses in circular crosssections do not align with the shear reinforcement, codes do not propose any efficiency factor to take into account this misalignment. After a thorough bibliographic research on the previous studies on the matter, the shortage of work accomplished on the topic has been assessed and the unsolved problems identified. Hence, an analytical model for evaluating the contribution of the transverse reinforcement in concrete members of solid circular cross section is presented in this paper. Considering transverse reinforcement as a continuous mean, an innovative formula for evaluating the shear transferred by both circular and spiral reinforcement in solid members is presented. Such formula is simplified and some efficiency factors are proposed, which cover most of the practical cases to be faced in the design process.
Traditionally, damage identification techniques in bridges have focused on monitoring changes to modal-based Damage Sensitive Features (DSFs) due to their direct relationship with structural stiffness and their spatial information content. However, their progression to real-world applications has not been without its challenges and shortcomings, mainly stemming from: (1) environmental and operational variations; (2) inefficient utilization of machine learning algorithms for damage detection; and (3) a general over-reliance on modal-based DSFs alone. The present paper provides an in-depth review of the development of modal-based DSFs and a synopsis of the challenges they face. The paper then sets out to addresses the highlighted challenges in terms of published advancements and alternatives from recent literature.
A meaningful contribution to the evaluation of heterogeneous public investments is described in this article. The proposed methodology provides a step towards sustainable urban planning in which decisions are taken according to clear, consistent and transparent criteria assisted by the MIVES multi-criteria analysis framework. The MIVES methodology combines multi-criteria decision making (MCDM) and multi-attribute utility theory (MAUT), incorporating the value function (VF) concept and assigning weights through the analytic hierarchy process (AHP). First, a homogenization coefficient is calculated to develop the Prioritization Index for Heterogeneous Urban Investments (PIHUI), so that non-homogenous alternatives may be comparable. This coefficient measures the need of society to invest in each public project through the consideration of its contribution to the regional balance, the scope of its investment, the evaluation of the current situation and the values of the city. Then, the MIVES multi-criteria framework is used to evaluate the degree to which each investment would contribute to sustainable development. Different economic, environmental and social aspects were considered through a decision framework, constructed with the three aforementioned requirements, five criteria and eight indicators. The case study conducted for the Ecology, Urban Planning and Mobility Area of Barcelona municipal council is presented in this article, showing how this method performs accurate, consistent, and repeatable evaluations.
Picolo, R.; Pialarissi Cavalaro, S.H.; Monte, R.; de Figueiredo, A.D. Cement & concrete composites Vol. 79, p. 117-132 DOI: 10.1016/j.cemconcomp.2017.02.002 Data de publicació: 2017-05 Article en revista
Cement and accelerator compatibility is critical for achieving proper mechanical performance in sprayed matrices. Few studies in the literature focus on establishing relationships between accelerated chemical reactions and the resulting mechanical properties of these matrices. The objective of this study is to evaluate the correlation between the chemical processes occurring in accelerated matrices and their mechanical strength development from a quantitative standpoint, elucidating the main mechanisms governing their performance. Hydration kinetics were analyzed by XRD and isothermal calorimetry, while mechanical properties were evaluated by needle and pin penetration resistance and compressive strength of extracted cores. Results showed the influence of the accelerated hydration and the evolution of phase composition on the development of mechanical properties of the matrices. Based on an extensive statistical analysis, multivariate linear regressions were established between the mechanical strength of sprayed mortars and the main chemical parameters influencing its development at early and late ages.
Infrastructure of communication, and in particular roads, have centuries of existence. The design, construction, operation, maintenance and dismantling have been adapted to the requirements and challenges of each historical period. Sustainability is one of the main challenges of our society, including as main pillars: economic, environmental and social aspects. The assessment of the sustainability of an infrastructure such as a road is a challenge still unsettled. Moreover, the misuse of the term sustainability poses a threat to achieve the objective of evaluating the sustainability of the roads. Given that the concept of sustainability implies different requirements and criteria, it seems reasonable to use multi-criteria methods in decision making. This article presents a brief review of methods to assess the sustainability of the infrastructure. It also proposes the MIVES method to assess the sustainability of roads. It is a multi-criteria method which includes the three main pillars of sustainability: economy, environment and society. The article concludes with an example of application for prioritization of investments in rural roads and its potential conversion in roads of Provincial Government.
Currently, decisions on the maintenance and repair of infrastructural assets, structures in particular, are mostly based on the results of inspections and the resulting condition index, neglecting system robustness and therefore not making optimal use of the limited funds available. This paper presents a definition and a measure of structural robustness in the context of deteriorating structures which are compatible with asset management systems for optimal maintenance and repair planning. The proposed index is used to define the robustness of existing reinforced concrete (RC) structures to rebar corrosion. Structural performance and the corresponding reliability index are assessed using combined advanced reliability and structural analysis techniques. Structural analysis explicitly includes deterioration mechanisms resulting from corrosion, such as reinforcement area reduction, concrete cracking, and bond deterioration. The first-order reliability method, combined with a response surface algorithm, is used to compute the reliability index for a wide range of different corrosion levels, resulting in a fragility curve. Finally, structural robustness is computed and discussed based on the results obtained. A robustness comparison of different structures can then be used to determine structural types more tolerant to corrosion and these results used for planning maintenance and repairs.
This paper reviews the simplified procedure proposed by Ghosn and Sivakumar to model the maximum expected traffic load effect on highway bridges and illustrates the methodology using a set of Weigh-In-Motion (WIM) data collected on one site in the U.S.A. The paper compares different approaches for implementing the procedure and explores the effects of limitations in the site-specific data on the projected maximum live load effect for different bridge service lives. A sensitivity analysis is carried out to study changes in the final results due to variations in the parameters that define the characteristics of the WIM data and those used in the calculation of the maximum load effect. The procedure is also implemented on a set of WIM data collected in Slovenia to study the maximum load effect on existing Slovenian highway bridges and how the projected results compare to the values obtained using advanced simulation algorithms and those specified in the Eurocode of actions.
Para llevar a cabo el mantenimiento preventivo de los edificios de una manera eficaz es importante contar con una escala unificada de posibles defi ciencias existentes. Esta es la hipótesis que los autores plantean a continuación
de la Fuente, A.; Armengou, J.; Pons-Valladares, O.; Aguado, A. Journal of civil engineering and management (Spausdinta) Vol. 23, num. 2, p. 194-203 DOI: 10.3846/13923730.2015.1023347 Data de publicació: 2017-02 Article en revista
A multi-criteria decision-making system based on the MIVES method is presented as a model for assessing the global sustainability index scores of existing wind-turbine support systems. This model is specifically designed to discriminate between tower systems in order to minimize the subjectivity of the decision and, thus, facilitate the task of deciding which system is best for a given set of boundary conditions (e.g., height, turbine power, soil conditions) and economic, social and environmental requirements. The model’s versatility is proven by assessing the sustainability index of an innovative new precast concrete tower alternative also described in this paper. As a result of this analysis, some points of improvement in the new system have been detected.
This is an Accepted Manuscript of an article published by Taylor & Francis Group in Journal of Civil Engineering and Management on 2017, available online at: http://www.tandfonline.com/10.3846/13923730.2015.1023347
Overtime, bridge condition declines due to a number of degradation processes such as creep, corrosion, and cyclic loading, among others. Traditionally, vibration-based damage detection techniques in bridges have focused on monitoring changes to modal parameters. These techniques can often suffer to their sensitivity to changes in environmental and operational conditions, mistaking them as structural damage. Recent research has seen the emergence of more advanced computational techniques that not only allow the assessment of noisier and more complex data but also allow research to veer away from monitoring changes in modal parameters alone. This paper presents a review of the current state-of-the-art developments in vibration-based damage detection in small to medium span bridges with particular focus on the utilization of advanced computational methods that avoid traditional damage detection pitfalls. A case study based on the S101
bridge is also presented to test the damage sensitivity to a chosen methodology.
Consistente en una solución compuesta de dos agentes antimicrobianos, uno bactericida y fungicida y otro alguicida y fungicida, un agente desaireante y un medio vehicular. El primer agente antimicrobiano de la familia de los policlorofenoxifenoles y se incorpora entre un 20% y un 40% sobre peso seco. El segundo de la familia de las isotiozolonas y se incorpora entre un 15% y un 20% sobre peso seco. El agente desaireante es un desaireante iónico, incorporado entre un 5% y un 10% sobre peso seco. Y el medio vehicular es filler calizo que se incorpora entre un 36% y un 76% sobre peso seco. El uso es para masa de hormigón y/o mortero, para capa de revestimiento superficial tipo lechada cementosa o para pintura en base cemento, en dosis entre un 0,1 y 0,5%.
Picolo, R.; Pialarissi Cavalaro, S.H.; Segura, I.; Hernández, M.; Ranz, J.; Figueiredo, A. Materials and design Vol. 113, p. 341-352 DOI: 10.1016/j.matdes.2016.10.022 Data de publicació: 2017-01 Article en revista
This paper focuses on the characterization of setting and hardening of accelerated cementitious matrices by ultrasound propagation velocity, correlating these processes with chemical parameters and the phase evolution obtained by in situ XRD. Evolution of temperature and determination of setting times complemented this analysis. The technique employed provided a continuous monitoring of the setting and hardening of the hydrating matrix and was susceptible to changes in accelerator reactivity and phase composition. Results showed that ettringite formed by accelerator reaction improves the solid-phase interconnectivity and increases initial ultrasound velocity. P-wave propagation during the acceleration period is directly proportional to alite and C3A degrees of hydration. The influence of AFm phases to increase ultrasound velocity is stronger than ettringite and C-S-H. Based on an extensive statistical analysis, multivariate linear regressions were established between ultrasound velocity and the main chemical properties influencing its evolution, leading to a better comprehension of how these parameters are related.
If we are to monitor the chemical processes in cementitious materials, then pH assays in the pore solutions of cement pastes, mortars, and concretes are of key importance. However, there is no standard method that regulates the sample-preparation method for pH determination. The state-of-the-art of different methods for pH determination in cementitious materials is presented in this paper and the influence of sample preparation in each case. Moreover, an experimental campaign compares three different techniques for pH determination. Its results contribute to establishing a basic criterion to help researchers select the most suitable method, depending on the purpose of the research. A simple tool is described for selecting the easiest and the most economic pH determination method, depending on the objective; especially for researchers and those with limited experience in this field.
Fibre-reinforced concrete (FRC) is a suitable alternative to the traditional reinforced concrete used in the manufacture of precast segments used to line tunnels excavated with a tunnel boring machine (TBM). Moreover, its use as a structural material has been approved by several national codes and by the current fib Model Code (2010). The use of FRC in segmental linings confers several technical and economic advantages, evidenced by the fact that structural fibres have been used to partially or entirely replace reinforcing bars in many TBM tunnels built over the past 20 years or currently under construction. FRC could also have been used in other tunnels, which are currently in the planning stage or under construction. However, despite its technical suitability and approval in current codes, the use of FRC was not possible in some cases. The impediment has sometimes been an incomplete understanding of the structural behaviour of the material, but a more general motive has been that comparisons of materials have taken into account only direct material costs and have not considered indirect costs or social and environmental factors. The aim of the present research is to develop a method for analysing the sustainability of different concrete and reinforcement configurations for segmental linings of TBM tunnels using the MIVES method (a multi-criteria decision making approach for assessing sustainability). This MCDM method allows minimising subjectivity in decision making while integrating economic, environmental and social factors. The model has been used to assess the sustainability of different alternatives proposed for manufacturing the segmental tunnel lining for the extension of the rail line of Ferrocarrils de la Generalitat de Catalunya (FGC) to Terminal 1 of El Prat Airport in Barcelona.
de la Cruz, C.; Ramos, G.; Hurtado, W. IOP Conference Series: Materials Science and Engineering (Online) Vol. 175, p. 1-11 DOI: 10.1088/1757-899X/175/1/012060 Data de publicació: 2017 Article en revista
The difference between self compacting concrete (SCC) and conventional concrete (CC) is in fresh state, is the high fluidity at first and the need for vibration at second, but in hardened state, both concretes must comply with the resistance specified, in addition to securing the safety and functionality for which it was designed. This article describes the tests and results for shrinkage and creep at some medium strength Self Compacting Concrete with added sand (SCC-MSs) and two types of cement. The research was conducted at the
Laboratorio de Tecnología de Estructuras (LTE) of the Universitat Politécnica de Catalunya (UPC), in dosages of 200 liters; with the idea of evaluating the effectiveness of implementation of these new concretes at elements designed with conventional concrete (CCs).
This is the first publication ever focusing strictly on the creep behaviour in cracked sections of Fibre Reinforced Concrete (FRC). These proceedings contain the latest scientific papers about new testing methodologies, results and conclusions of multiple experimental campaigns and recommendations about significant factors of long-term behaviour, experiences from more than ten years of creep testing and some reflections about future perspectives on this topic. This book is an essential reference for all researchers of creep behaviour on FRC. This volume is the result of the efforts of the RILEM TC 261-CCF, that has been working since 2014 to develop standardized methodologies and guidelines to compare results from different laboratories and get a better understanding of the significant parameters related to creep of FRC.
Aguado, A.; del Caño-Gochi, A.; de la Cruz-Lopez, M.; Torrents, J.M.; Lara, M.; Armengou, J.; Casanovas, M.; Pons-Valladares, O.; Segura, I.; Pardo, F.; de la Fuente, A.; Pujadas, P. Projecte R+D+I competitiu