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La evaluación de las estructuras existentes es un tema prioritario, de gran importancia económica, en un número creciente de países de todo el mundo ya que en muchos lugares una parte cada vez mayor del mercado de la construcción se centra en las actuaciones relacionadas con edificios, puentes y otras obras de ingeniería civil que ya existen. Actualmente, los Eurocódigos, que se utilizarán en todos los estados miembro del Comité Europeo de Normalización, CEN, y posiblemente en más y más países fuera de este espacio, están principalmente enfocados al proyecto de nuevas estructuras. El empleo de métodos orientados al dimensionado para evaluar las estructuras existentes a menudo conduce a un alto grado de conservadurismo. Las consecuencias económicas, ecológicas y sociopolíticas podrían ser significativas si se condenaran como inseguras unas estructuras cuyas prestaciones son satisfactorias, llevando a una inversión innecesaria de recursos en su rehabilitación o desmantelamiento y sustitución. Por esta razón, la evaluación de las estructuras existentes a menudo requiere el uso de métodos refinados que van más allá del alcance de las reglas normalizadas para el proyecto de nuevas estructuras. Consecuentemente, en los últimos 20 años, se han desarrollado métodos para la evaluación de las estructuras existentes en muchos países a nivel nacional. Sin embargo, estos métodos aún no se han coordinado entre sí y su implementación en la práctica diaria suele ser escasa. Existe por ello una necesidad urgente de fusionar los diversos enfoques nacionales en un conjunto de reglas generalmente aceptadas, coherentes y armonizadas para las estructuras existentes que complementen las reglas para el proyecto de nuevas estructuras. CEN tomó la iniciativa de iniciar un proyecto para desarrollar nuevas normas técnicas europeas para la evaluación y la rehabilitación de las estructuras existentes. Está previsto que el desarrollo de la parte correspondiente del Eurocódigo se logre en tres pasos. Ya se han completado dos de estos pasos, a saber, la preparación de un Informe Científico y de Política y, una vez adoptado por los Organismos Nacionales de Normalización de los estados miembro, la conversión de este documento en una Especificación Técnica de CEN. El tercer paso, la evolución de la Especificación Técnica en una Parte del Eurocódigo, EN, está actualmente en progreso. Sobre este trasfondo, en el presente artículo se analizan las diferencias más relevantes entre la evaluación y el proyecto desde el punto de vista de la fiabilidad estructural y se identifican algunos aspectos que deberían dar lugar a unas reglas adicionales en futuras normas dedicadas a las estructuras existentes.

In bridge planning, the successful translation of the many conditioning factors into a solution that meets all safety requirements while also addressing considerations such as economy and elegance ...

Marie-Claude Schöpfer Pfaffen: Verkehrspolitik im Mittelalter. Bernische und Walliser Akteure, Netzwerke und Strategien (Vorträge und Forschungen, Sonderband 55). Hg. vom Konstanzer Arbeitskreis für mittelalterliche Geschichte. Ostfildern: Jan Thorbecke Verlag 2011. 374 S., etwa 14 z. T. farb. Abb. ISBN 978-3-7995-6765-7. € 58,–

The relatively high failure rates, with important consequences in many cases, suggest that the implicitly acceptable risk levels corresponding to temporary civil engineering structures and activities might exceed the bounds of normally acceptable levels associated with different societal activities. Among other reasons, this may be attributed to the lack of a rational approach for the assessment of risks associated with the different technologies supporting these activities in general, and for structures in particular. There is a need for establishing appropriate target reliability levels for structures under temporary use taking into account specific circumstances such as reduced risk exposure times. This issue is being addressed in this article. Acceptance criteria for building‐structure‐related risks to persons obtained in prior studies are adapted to the special circumstances of nonpermanent risk exposure. Thereby, the general principle followed is to maintain the same risk levels per time unit as for permanently occupied buildings. The adaptation is based on the statistical annual fatality rate, a life safety risk metric that allows for a consistent comparison of risks across different societal activities and technologies. It is shown that the target reliability indices taking account of the temporary use of buildings might be significantly higher than the values suggested for permanently used structures.

Las normas estructurales actuales, como los Eurocódigos, no proporcionan un marco coherente para el diseño o evaluación de las estructuras en condiciones de uso temporal. Los requisitos de fiabilidad de los sistemas temporales propuestos en el presente estudio pretenden garantizar los mismos niveles de riesgo aceptables por unidad de tiempo que para las estructuras permanentes en las mejores prácticas actuales. Los resultados obtenidos muestran que el índice de fiabilidad para los elementos estructurales aumenta significativamente con la disminución de los tiempos de exposición al riesgo. Por el contrario, los valores de diseño para las acciones variables pueden reducirse en función de la duración de construcción, como se ilustra en un caso práctico: el análisis de un sistema de andamiaje móvil para el montaje de un puente.

La corrosión de la armadura es uno de los problemas de mayor impacto económico en el ciclo de vida de las estructuras de hormigón por lo que es necesario optimizar las estrategias de reparación de estructuras corroídas. Sin embargo, a nivel internacional no hay códigos que permitan una evaluación por lo que se incluirán criterios en la revisión del Eurocódigo 2 para la evaluación de estructuras existentes y deterioradas. En el presente artículo se resumen el trabajo realizado en el proyecto Contecvet, financiado por la Comisión Europea, y los avances realizados desde entonces. En las estructuras existentes, una primera precisión consiste en determinar si el deterioro ha alcanzado a la armadura, y en ese caso, cuánto se ha afectado al comportamiento estructural. Calculada la velocidad de corrosión a partir de los datos tomados en la propia estructura es posible estimar la velocidad de avance del deterioro mediante los modelos desarrollados y la vida residual remanente. Se resumen los modelos y expresiones para estimar la capacidad resistente de estructuras con armaduras corroídas a considerar en la elaboración del nuevo Eurocódigo 2.

Trabajo presentado en el Joint fib-RILEM Workshop Modelling of Corroding Concrete Structures, celebrado en Madrid (España), los días 22 y 23 de noviembre de 2010, The growing interest in upgrading existing reinforced concrete structures or extending their service life, and in ensuring greater durability in new designs, has led to a need for resistance models that take deterioration processes into account to verify structural safety. Bond activation between reinforcing steel and concrete is of cardinal importance in this context. A number of experimental studies have been conducted in recent years on bond failure, which normally leads to brittle behaviour. The findings have diverged rather widely, however, due primarily to differing test conditions. The present paper presents an experimental programme for eccentric pull-out tests in which specimens were subjected to both accelerated and natural corrosion in an attempt to surmount these inconsistencies. It also introduces an embedded fibre-optic sensing system with corrosion-resistant fibre Bragg grating sensors and discusses some of the findings.

With the growth and ageing of the stock of existing structures, structural assessment and retrofitting are fast acquiring a significant role in the construction industry. The benefits of upgrading existing reinforced concrete (RC) structures or extending their service life and of ensuring greater durability in designs for de novo construction have led to a need to include deterioration as a factor in structural safety models. Bond between reinforcing steel and concrete is of cardinal importance in this respect. The present paper proposes a unified formulation for assessing bond strength in corroded and non-corroded steel bars, and an associated model to accommodate the effect of transverse pressure where appropriate. The formulation is the result of applying multiple linear regression analysis to a database built from the findings of over 650 bond tests on corroded and non-corroded reinforcing steel reported in the literature. The data collected include a wide range of variables affecting bond strength, such as bar diameter, concrete compressive strength, concrete cover, anchorage length, confinement ratio and cross-sectional loss. A number of statistical criteria are used to compare the proposed formulation to the other bond strength assessment models, including the fib Model Code 2010 proposal for corroded steel bars. Further to the statistical tests conducted, the model proposed can be usefully applied to assess the structural safety of corroded RC members.

Bridge building entails considerable risk, as attested to by the relatively frequent occurrence of worksite accidents. In the accident reported on here, an overhead gantry derailed during the construction of the last of 13 spans on one of two nominally identical parallel bridges composing a precast concrete girder viaduct. As no prior anomalies had been detected, the structure was the object of a detailed forensic inquiry. The most likely hazard scenario was inferred from the mutually reinforcing findings gleaned from numerical calculations, experimentation, eyewitness accounts, and reconstruction of the accident sequence. Organizational flaws such as less-than-optimal interfacing and data exchange among the actors involved in viaduct construction were observed to be among the major underlying causes. The study showed that effective quality-assurance strategies, fluent worksite actor intercommunication, and a clear definition of tasks and responsibilities are of cardinal importance in preventing accidents.

Most building design codes distinguish structural reliability levels in terms of failure consequences, for which they normally define consequence classes based on building type and use. Although readily applicable in everyday practice, that approach may entail adopting inconsistent safety requirements. Such a significant drawback could be minimised by establishing separate reliability levels for key members on the grounds of the potential consequences of their collapse. Further to those concerns, this paper proposes a series of consequence classes determined in keeping with the number of persons at risk in a given collapse scenario and the extent of the respective damage. Consequence class-related models for predicting loss of life are derived from statistical assessments of data on over 150 collapsed buildings. The models developed estimate the number of fatalities and conditional probability of death of building users under given collapse circumstances. In addition to their utility in establishing target reliability values, these models can be applied in risk analysis of specific building structures, especially where the potential consequences of failure are high.

Accidental hazards are associated with large uncertainties regarding their occurrence probability, their effects on a structure and the possible consequences these effects might entail in case of failure. Consequently, decision-making related to safety accounting for such hazards is difficult and prone to be based on irrational grounds. Gas explosions in buildings are a good example therefore. Although dealt with in many codes, they are seldom accounted for in design of building structures. As a consequence, the associated risks are often ignored or sometimes consciously accepted. If this is a justified practice cannot be easily judged however, since under the implicit approach adopted in practice for assuring structural safety the risks are not quantified nor are the acceptable risk levels established. On this background, the paper explores methods and tools for the practical application of explicit risk analysis in connection with the effects of gas explosions on RC structures. A procedure is established to determine structure-related risks to persons and applied to a representative set of structures designed according to current best practice. Target reliabilities for the design of key elements are deduced from the findings. Such target values facilitate rational decisions on both, the need and the appropriate choice of risk-reduction measures to counteract the effects of gas explosions in buildings.

The assessment of an existing structure to determine its suitability for present and future use entails different sorts of problems than encountered when designing new structures. The differences revolve essentially around the nature of the information available. In existing structures, deteriorated or otherwise, the accuracy of the models used for such assessments can usually be improved by acquiring more data. The most accurate way to find actual load and resistance would be to conduct a probabilistic analysis using site data. This is a time-consuming process, however, calling for a working knowledge of probabilistic methods that may not be suited to everyday use by practising engineers. For this reason, in the past few years various studies have been conducted to develop assessment approaches, compatible with Eurocodes, which include the same verification format as normally applied for designing new structures. In this paper, the application of several of these approaches is illustrated by means of the reliability verification of one of the main beams of the reinforced concrete structure of an industrial building from the 1940s, recently transformed into a cultural centre. The obtained results are discussed and compared to the findings of a full probabilistic analysis.

Beiträge zur Lehrerinnen- und Lehrerbildung 34 (2016) 3, S. 344-358, Seit der Freigabe des Lehrplans 21 gibt das neue Integrationsfach «Räume, Zeiten, Gesellschaften» (RZG) viel zu reden. Anders als im Bereich «Natur und Technik» (NT), das drei Naturwissenschaften vereint, prallen bei RZG naturwissenschaftliche, historische und geisteswissenschaftliche Perspektiven aufeinander, die sich nur bedingt gleichschalten lassen. Daher sind Berührungspunkte geringer als in der Fachbezeichnung suggeriert und eine Bereichsdidaktik drängt sich primär aus formalen Gründen auf. Zudem sind die Kompetenzen im Lehrplan 21 für Geografie und Geschichte separat ausgewiesen. Es stellt sich aber dennoch die Frage, wie der Umgang mit einem neuen Sammelfach aussehen soll., Since the release of the curriculum «Lehrplan 21», the new integrated school subject «Räume, Zeiten, Gesellschaften» («Spaces, Times, Societies», RZG) has caused much debate. Unlike «Natur und Technik» («Nature and Technology», NT), which unites the three natural sciences, in RZG there is a clash of perspectives from science, history and humanities, which can only be resolved to a certain point. Consequently, the synergies are smaller than suggested in the description of the subject. Moreover, the competences for geography and history are described separately in «Lehrplan 21». Still, the question remains how a new multiple subject should be treated.

Civil construction is a highly uncertain endeavour that entails a considerable risk, as attested to by the succession of incidents and accidents reported the world over. The reasons for this situation need to be identified before strategies can be adopted with a view of reducing the construction-related risks. Taking the forensic investigations of a series of accidents as a starting point, this article explores the generally applicable lessons learnt from those case studies. Such surveys show that the problems to be dealt with in everyday practice are rather elementary and often attributable to human error. Basic principles and recommendations are therefore put forward for the design, erection and use of temporary structures in general and ancillary equipment for construction processes in particular, aimed at reducing the risks associated with such activities. Moreover, as there is no general consensus on reliability requirements for the temporary structures, this paper addresses the establishment of acceptable life safety risk and the associated reliability levels. The requirements put forward aim to ensure the same statistical fatality rate per unit of time as for the permanent structures. The effect of the established principles, recommendations and requirements on the design and assembly of the temporary structures is illustrated by means of an example.

Resumen El proyecto de Ampliacion del Complejo Ferroviario de Atocha Fase I se desarrolla con el principal objetivo de permitir la puesta en servicio de un nuevo modelo de explotacion ferroviaria a fin de incrementar la capacidad de la estacion de Puerta de Atocha, separando los flujos de llegadas y salidas. Se describen a continuacion los antecedentes, el ambito de la ampliacion y los motivos de la misma, asi como los principales elementos estructurales y las actuaciones mas significativas realizadas dentro del proyecto de ampliacion, distinguiendo entre las intervenciones realizadas en las vias y las llevadas a cabo sobre la estructura del edificio ya existente. Asimismo, se detallan algunas consideraciones sobre las acciones aplicadas en el calculo de las nuevas marquesinas y sobre los analisis realizados mediante calculo dinamico de fluidos para verificar los coeficientes de presion adoptados inicialmente a partir de extrapolaciones de normativas de acciones vigentes, dada la compleja geometria de las nuevas cubiertas de la estacion de Atocha. Por ultimo, se describen la logistica y la planificacion realizadas durante la ejecucion de las obras, teniendo en cuenta todos los escenarios posibles y la necesidad de simultanear una gran cantidad de actividades en un espacio y tiempo limitados (cortes de tension, cajas de vias, trabajos con lineas de alta tension…). La complejidad de este estudio ha sido enorme, considerando las excepcionales limitaciones derivadas de las necesidades de explotacion de la estacion de AVE durante la fase de ejecucion del proyecto.

Stage I of the enlargement of Atocha Railway Station aimed primarily to adapt the facility to a new operating model, raising the station's capacity essentially by separating arriving and departing passenger traffic. This article describes the project background, scope and justification, as well as the main structural members and most significant works involved in the enlargement, distinguishing between construction in platforms and tracks and existing facility restructuring. In light of the complex geometry of the new roofs over Atocha Station, computational fluid dynamics (CFD) techniques were deployed to verify the pressure coefficients initially adopted for the new platform canopies by extrapolation from the existing legislation. The structural engineering involved is addressed. Lastly, logistics and planning are discussed, with an account of all the possible scenarios and the challenge of performing many activities simultaneously on a tight schedule in limited quarters (power outages, track beds, high voltage works,…). The exceptional constraints inherent in the need to maintain high-speed train (“AVE”) service during the works intensified the overall complexity.

The design of concrete structures is usually made by means of a performance approach based on strength tests carried out following testing conditions agreed by convention. A similar approach should also be followed in the case of durability design regarding reinforcement corrosion. This type of consideration enables the establishment of verification of durability in categories. Three categories have been identified: (I) it would be the prescriptive method already given in present codes based on “deemed-to-satisfy” rules, (II) this is based in the testing through “durability indicators” that where still not quantification of the time to reach a limit state is explicit but the minimum life time is assured through performance based tests, (III) it is the category in which the calculation of aggressive ingress through models having explicit the time is made including probabilistic treatments. In the paper in addition to the comment on the most common methods of calculation of the chloride ingress and their limitations it is illustrated how for level II and III the measurement of the electrical resistivity results a very suitable proposal due to this parameter can be measured in a non-destructive test and serves to quality control. It is not only a performance test (level II) but it can be included in models of both the initiation and propagation periods. For the time to corrosion onset, the electrical resistivity represents the porosity and its connectivity and therefore can be used to model transport processes. It also results very suitable for measuring concrete aging and then accounting for the reduction of the diffusion coefficient with time. Concerning the propagation period, the electrical resistivity is an indication of the moisture content of concrete and therefore, it has a certain relationship with the corrosion cement. A model is proposed in which the resistivity is introduced in the square root of time law. Finally the paper comments on the tests methods used for the measurement of the diffusion coefficient and of resistivity

Italian ryegrass (Loliummultiflorum Lam. ssp. italicum Volkart ex Schinz et Keller) thrives well in permanent grassland in mild and moist regions of Switzerland. Ecotypes of Italian ryegrass from Swiss permanent meadows have often been used successfully as the base material of breeding programmes. However, their agronomic performance per se has never been studied in detail. Therefore, field trials were conducted to assess the potential of this semi-natural genetic resource for use in breeding. Twenty ecotype populations were collected in different geographical regions in 2003 and seed was increased. Plot trials with 20 ecotype populations were conducted 2005–2007 at three locations, supplemented by row trials at two additional locations, and including four currently recommended cultivars as controls. Average performance in terms of yield, vigour and resistance to snow mould of ecotypes was superior to the cultivars. Depending on the characteristic, between three and 16 of the 20 ecotypes performed significantly better than the cultivars mean. However, resistance against crown rust of all ecotypes was significantly poorer than that of the cultivars. Correlation and regression analysis showed that more eastern and more northern collecting sites harboured better performing ecotypes. However, the most consistent site related factor favouring performance of the ecotypes in terms of yield, vigour, snow mould and Xanthomonas resistance was a low abundance of species which are typical of Arrhenatheretum type meadows. Data from the plot trials were related to results obtained with spaced plants at a single site, either in a seedling nursery or in the greenhouse. Resistance against crown rust was extremely well predicted by spaced plant observations. Xanthomonas resistance observed after artificial inoculation in the greenhouse was also significantly, but less closely correlated with field observations. An early date of ear emergence as observed on spaced plants was associated with high annual yield in the plot trials. It is concluded that in intensively managed habitats, natural selection has resulted in ecotype populations of Italian ryegrass which are highly promising for use in breeding. Individual plant selection for resistance can be expected to efficiently reduce their high susceptibility to crown rust.

Herbage yield trials are necessary to test if candidate varieties are well suited for organic conditions. In order to elucidate a particular suitability for organic conditions, we run such trials in parallel under both organic and conventional conditions. Here, we report on second and third year results of the sowings 2004 and 2005. These trials are part of a targeted breeding programme for organic conditions. Irregular colonisation of pure grass plots with adventitious plants, in particular white clover, was recognized as a major constraint to the quality of the results obtained under organic conditions. The coefficients of variance in dry matter yield almost doubled when compared to conventional trials, and significant differences in annual yield among varieties were rare. However, when herbage yield was corrected for the estimated fraction of adventitious plant colonization at each cut, the number of instances with statistically significant differences for annual yield among varieties increased more than fourfold. Dry matter yields under organic and conventional conditions were significantly and positively correlated. However, analysis of variance showed a significant culture type by variety interaction for annual dry matter yield in 12 out of 24 trials. When diploid and tetraploid varieties of the same Lolium species were tested in one common trial, only tetraploid varieties were identified as being particularly well suited for organic conditions, while in these trials, the great majority of apparently poorly suited varieties were diploid. This suggests that breeding tetraploid Lolium varieties is promising when aiming at a favourable response to organic agriculture.

Introduction Myofibroblastoma of the breast is a rare benign stromal tumour seen predominantly in men. The gross appearance is that of a well-circumscribed nodule, characteristically small, seldom exceeding 3 cm. We present a case of an unusually large myofibroblastoma, which mimicked a malignant breast tumour. Case presentation A 65-year-old man presented with a rapid enlargement of the right breast over 6 weeks. Examination revealed a firm 15 cm hemispherical lump occupying the whole of the right breast with peau d'orange appearance of the overlying skin and distortion of the nipple. The clinical and radiological features suggested the possibility of sarcoma of the breast. However, a guided Tru-Cut biopsy was inconclusive. A mastectomy was performed to remove the tumour, which weighed more than 2 kg. Histopathology and immunocytochemistry revealed a mixed classical and collagenised type of myofibroblastoma. The patient is well with no evidence of recurrence 5 years after the mastectomy. Conclusion This unexpected presentation of an unusually large myofibroblastoma in a male breast is the largest reported to date. Myofibroblastomas can mimic malignant neoplasms and the clinical significance of this entity lies primarily in its recognition as a distinctive benign neoplasm.

Presstessed and reinforced precast concrete structures behaviour in seismic areas depends mostly on the kind ofjoint between elements. The final configuration ofthe structure for resisting actions is granted by the e.xecution ofrigid connections during the building phase. When joints in precast structures have continuity ofthe reinforcement in the connections, the behaviour ofthese structures in seismic areas is quite similar to cast-in-situ ones. Therefore, no limitation should be applied and the same requirements statedfor common structures should be validatedfor precast ones. El comportamiento de las estructuras prefabricadas de hormigón armado y pretensado en zonas sísmicas depende, fundamentalmente, del tipo de unión que vincula los diferentes elementos prefabricados. Éstos se completan durante el proceso de montaje mediante la ejecución de los nudos, dotando a la estructura de su configuración definitiva para resistir las acciones de servicio. Cuando las estructuras prefabricadas presentan una tipología de unión en la que se da continuidad a las armaduras que configuran los nudos rígidos, se puede afirmar que el comportamiento de las mismas en zonas sísmicas es análogo al que corresponde a una estructura de hormigón construida "in situ", sin ningún tipo de limitación y, por tanto, son de aplicación las mismas exigencias normativas que las utilizadas, con carácter general, para el proyecto y construcción de las estructuras de hormigón estructural.

Trabajo presentado en el IABSE Symposium: Engineering for Progress, Nature and People, celebrado en Madrid (España), del 3 al 5 de septiembre de 2014, The present paper proposes a semi-empirical formulation for assessing bond strength in corroded and non-corroded steel bars for both pull-out and splitting failure. It was obtained by applying multiple linear regression analysis to a database containing over 650 tests on corroded and non-corroded bars, including tests conducted in a prior study and data from literature. The database used covered a wide range of variables affecting bond strength, such as bar diameter, concrete strength, concrete cover, anchorage length, confinement ratio and corrosion-induced cross-sectional loss. A number of statistical criteria were used to analyse the proposed formulation and the effect of the explanatory variables. The results were compared to the findings for other formulations, including the fib Model Code 2010 proposal for corroded bars. The formulation proposed proved to be usable in the structural assessment of corroded reinforced concrete members.