Natural corrosion in reinforced concrete structures

Among the threats to the durability of concrete structures, corrosion of the reinforcement bars is undoubtedly the most common one. Corrosion damages impair safety and durability of infrastructure, and assessment of the safety is challenging due to the complex nature of the corrosion process. Furthermore, research on the topic often requires adapting results from short-time laboratory tests, where corrosion of the reinforcement bars is induced using impressed current, to the reality of existing structures. The use of impressed current results in differences in type and distribution of corrosion products.Naturally corroded specimens are hence the necessary bridge between the knowledge acquired from artificially corroded specimens and the application to real structures.This works investigates the structural effects of natural, chloride-induced corrosion in reinforced concrete structures. Specifically, three research questions were investigated. First, the bond and anchorage of naturally corroded plain bars was studied using 3-point bending and pull-out tests. The tests were designed to be applied to specimens taken from a decommissioned bridge from the 1930s. The bond capacity of plain bars was observed to be significantly higher than in results obtained from laboratory tests on similar bars. Significant factors influencing the effect of corrosion damages on the bond were casting position and presence of stirrups. Finite element analyses were used to further investigate the bond-slip behaviour of the tested specimens. The results highlighted the effect of the loss of bond at yielding on the structural behaviour of the specimens. The second question looked into the characteristics of the corrosion products and the surrounding concrete; this is relevant to assess corrosion damages in existing structures. Neutron imaging and X-ray computed tomography were used to obtain qualitative and quantitative data on corrosion damages in a naturally corroded specimens, including iron to rust ratio. Comparison with an artificially corroded specimen showed differences in distribution of the corrosion products. Finally, possible correlations between transversal cracks and corrosion damages was investigated. A dataset was compiled from experiments available in literature. In the selected studies, corrosion of the steel reinforcement resulted from exposing laboratory specimens, pre-cracked in 3-point bending, to chloride environments. No clear correlation between surface crack width and corrosion characteristics was found, but corrosion pits were shown to likely appear in the proximity of transveral cracks.To conclude, this work highlights the complexity of the corrosion process and argues that a thorough understanding of the material and environmental characteristics influencing this process is necessary to properly assess existing structures. Tests on naturally corroded structures are a fundamental step towards acquiring this knowledge

Ricerche iconografiche tra agiografia e devozione popolare: Il “Miracolo del pane di sant’onofrio bambino”

The iconographic analysis of a recently discovered painting, representing a variation in the traditional hagiography of St. Onuphrius, offers the chance for a historical and  artistic excursus into the society and the religious life of the XVI century. This article focuses on the existence of devotional practices which were so widespread and  influential that even the most authoritative hagiographic publications had to take them into account. What emerges in particular is the role played by the Congregation of  Hermits of St. Jerome which organized an efficient and well-planned devotional strategy during the XVI century in order to associate St. Onuphrius with their founder, Blessed Pietro Gambacorta from Pisa.Keywords: Iconography – Baroque – Catholic Devotio

Corrosion of Steel in Concrete Seen through Neutron and X-Ray Tomography

No abstract availabl

Corrosion of naturally corroded, plain reinforcing bars

Reinforced Concrete is known to be susceptible to corrosion damages. Corrosion, by reducing strength and ductility of the reinforcing bar and modifying the steel/concrete interface, hinders the overall safety of the structure. This work investigates the bond of naturally corroded, plain reinforcing bars. Specimens were taken from an 80-year-old bridge and tested using pull-out and 3-point bending tests. Additionally , neutron and X-ray tomography is used to observe the distribution of corrosion products. Results highlight the influence of casting position on the bond of plain bars. Specifically, the distribution of corrosion products is influenced by the bleeding zone underneath top-cast bars. Corrosion products are shown to deposit in macro-pores and to adhere to the bar

Mixed-integer optimal control under minimum dwell time constraints

AbstractTailored Mixed-Integer Optimal Control policies for real-world applications usually have to avoid very short successive changes of the active integer control. Minimum dwell time (MDT) constraints express this requirement and can be included into the combinatorial integral approximation decomposition, which solves mixed-integer optimal control problems (MIOCPs) to $$\epsilon$$ ϵ -optimality by solving one continuous nonlinear program and one mixed-integer linear program (MILP). Within this work, we analyze the integrality gap of MIOCPs under MDT constraints by providing tight upper bounds on the MILP subproblem. We suggest different rounding schemes for constructing MDT feasible control solutions, e.g., we propose a modification of Sum Up Rounding. A numerical study supplements the theoretical results and compares objective values of integer feasible and relaxed solutions

La comunicazione politica tra Bisanzio e il Nuovo Mondo, passando per Creta e Venezia. : I trattati di Menandro Retore

La comunicació política entre Bizanci i el Nou Món, passant per Creta i Venècia. Els tractats de Menandre el RètorL’article aprofundeix en la circulació de dos tractats del sofista Menandre de Laodicea i la seva influència en la composició, l’any 1577, dels qüestionaris de les Relacions Geogràfiques de les Índies. A més, aquesta contribució pretén analitzar de quina manera la retòrica epidíctica, àmpliament coneguda a Itàlia durant els segles XV i XVI gràcies a la presència de manuscrits grecs, fou utilitzada per construir estratègies de comunicació exitoses. El paper sociopolític del discurs epidíctic va ser entès especialment a Florència i a Venècia. Per tant, l’anàlisi de la circulació de tractats impresos i manuscrits des de Venècia fins Espanya fa llum sobre els usos polítics de la retòrica sofista a l’Europa del Renaixement.The political communication between Byzantium and the New World, passing through Creta and Venice. The treatises by Menander RhetorThis article focuses on the circulation of the two treatises of the sophist Menander of Laodicea and their role in the composition of the Relaciones geográficas questionnaires in 1577. Furthermore, it aims to analyze how epideictic rhetoric, which was widely known in Italy during the fifteenth and sixteenth centures thanks to the presence of Greek manuscripts, was adopted in order to build up successful communication strategies. The socio-political role of epideictic speech was well understood particularly by Florence and Venice.The printed and manuscript traditions of Menander’s tracts, from Venice to Spain, therefore, shed new light on the role of Sophistic rhetoric in RenaissanceEurope and on its political uses.La comunicación política entre Bizancio y el Nuevo Mundo, pasando por Creta y Venecia. Los tratados de Menandro el RétorEl artículo profundiza en la circulación de dos tratados del sofista Menandro de Laodicea y su influencia en la composición en 1577 de los cuestionarios delas Relaciones Geográficas de Indias. Además, la presente contribución pretende analizar cómo la retórica epidéctica, ampliamente conocida en Italiadurante los siglos XV y XVI, gracias a la presencia de manuscritos griegos, fue utilizada para construir estrategias de comunicación exitosas. El rol sociopolítico del discurso epidíctico fue especialmente entendido en Florencia y Venecia.Por lo tanto, el análisis de la circulación de tratados impresos y manuscritos desde Venecia hasta España arroja luz sobre los usos políticos de laretórica sofista en la Europa del Renacimiento.Victoria Pineda, in un articolo pubblicato nel 2000, considerava che i due trattati retorici attribuiti a Menandro di Laodicea erano stati usati nel 1577 come fonti per la redazione dei questionari delle Relaciones Geográficas de Indias.Seguendo questa intuizione, il presente contributo vuole analizzare come la retorica epidittica, che era ampiamente conosciuta in Italia tra il XV e il XVIsecolo grazie alla circolazione dei manoscritti greci, fu adottata per promuovere efficaci strategie comunicative. Il ruolo socio-politico del discorso epiditticofu particolarmente conosciuto a Firenze e a Venezia. La circolazione dei trattati di Menandro, manoscritti e a stampa, da Venezia alla Spagna, offrequindi un nuovo sguardo sul ruolo della retorica sofistica nell’Europa del Rinascimento e sui suoi usi politici

Bond of naturally corroded, plain reinforcing bars in concrete

In the past, reinforced concrete structures were built utilising plain reinforcement bars. Currently, this construction method is seldom considered by codes and research; however, many heritage structures are still standing and in need of proper assessment. In particular, there is a lack of knowledge on the effect of corrosion on the bond between concrete and plain reinforcement bars. To address this gap, pullout tests were performed on reinforced concrete specimens sourced from a decommissioned bridge originally constructed in 1935. The specimens were naturally corroded, as the use of accelerated corrosion techniques in structural tests is still debated. A total of 156 pullout tests were conducted on specimens with varying thicknesses. The pullout force, active and passive slip, and corrosion levels were measured. The effect of corrosion on the bond strength, and the amount of visible damage owing to the presence of corrosion products, were influenced by the casting position of the reinforcing bars. The presence of stirrups influenced the post-peak behaviour, increased the residual bond strength, and helped maintain the bond strength in the presence of cracks and spalling damage. Additionally, current code provisions were found to provide conservative values for the peak bond stress of plain reinforcing bars

Responsabilidad social empresaria

El siguiente artículo abordará una mirada coyuntural respecto de la situación en que se encuentran hoy las empresas frente a esta “obligación moral”, impuesta o requerida por la sociedad global, situación actual directamente ligada en materia de asistencia social, compromiso con la comunidad, y desarrollo e interacción con la misma. Hemos tomado diferentes visiones y enfoques de autores, partiendo de desarrollar las principales características de lo que queremos entender como responsabilidad social empresaria.Facultad de Periodismo y Comunicación Socia

Responsabilidad social empresaria

El siguiente artículo abordará una mirada coyuntural respecto de la situación en que se encuentran hoy las empresas frente a esta “obligación moral”, impuesta o requerida por la sociedad global, situación actual directamente ligada en materia de asistencia social, compromiso con la comunidad, y desarrollo e interacción con la misma. Hemos tomado diferentes visiones y enfoques de autores, partiendo de desarrollar las principales características de lo que queremos entender como responsabilidad social empresaria.Facultad de Periodismo y Comunicación Socia

Numerical assessment of bond-slip relationships for naturally corroded plain reinforcement bars in concrete beams

Reinforced Concrete (RC) heritage structures are often affected by corrosion. Consequently, knowledge about the effect of corrosion on the bond between reinforcing bars and surrounding concrete is critical when assessing the structural performance of these structures. In earlier work, structural tests were carried out on segments of edge beams taken from a decommissioned RC bridge. The specimens had naturally corroded plain reinforcement bars and three-point bending tests were conducted, to investigate their anchorage capacity. In this study, non-linear finite element analyses (NLFEA) were carried out to gain further insight into the bond behaviour of the tested specimens, including the effect of corrosion on the bond-slip relationship. Two different, one-dimensional (1D), bond-slip relationships were calibrated for each tested bar, to account for loss of bond upon yielding. The calibration process was based on a comparison between significant numerical and experimental results, including load–deflection curve, crack pattern and asymmetrical distribution of the yield penetration along the length of the bar. Good agreement between the FE analyses and experimental tests was observed. Finally, the calibrated bond-slip relationships for nine beams with different corrosion levels, casting positions, and visual damage are presented and discussed. The loss of bond at yielding and yield penetration asymmetry are both shown to be crucial factors for adequately describing structural behaviour