Dynamic behavior of masonry chimney with different reinforcement schemes

Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.This paper presents a structural analysis of a masonry chimney built in the 1950’s, which is currently being catalogued as local interest heritage. These structures exhibit insufficient tensile strength to resist the seismic action because the masonry is not reinforced. For this reason, the aim of this work is to analyze different structural reinforcement schemes so the chimney is capable of withstanding seismic actions. Ten numerical models, for nine reinforcement configurations, have been defined using Ansys software. A glass fiber reinforced cement composite was always used as reinforcement. For each model, a modal analysis and time history analyses were made. Five different synthetic accelerograms were used for the structural analysis, according to NCSE02 Spanish standard. The final reinforcement, capable of resisting the seismic action, consisted of a helicoid wrap and eight longitudinal stripes along the shaft, and the inner and outer reinforcement of all masonry walls of the base

In-plane shear cyclic behavior of windowed masonry walls reinforced with textile reinforced mortars

The current experimental study is focused on the mechanical performance of masonry walls under in-plane cyclic shear forces. All specimens were fabricated with a central window, in which the geometry considered the recommendations of the Spanish structural seismic design code. Windows represent a weak area in the masonry structure, in which there are stress concentrations responsible for crack initiation. In order to improve the mechanical strength and ductility, a reinforcement with a Textile Reinforced Mortar (TRM) was used on both sides of the wall. The performance of the unreinforced and reinforced masonry has been discussed in terms of strength and ductility gain, stiffness degradation and energy dissipation capacity. The experimental tests comprised an initial vertical preload, and shear cycles with increasing amplitude. All tests were monitored by means of traditional displacement transducers, and digital image correlation. The analysis of the images showed the time evolution of the overall crack distribution. The TRM effect could be observed as an increase of the mechanical strength (maximum shear from 120 kN to more than 300 kN), higher displacements (drift from 9 to 35 mm), and more energy dissipation (the cumulative energy loss from 2.7 to 12.7 kN·m). In addition, the TRM reinforcements were capable of controlling the crack initiation and growth. The widespread crack along mortar joints observed in the unreinforced masonry became localized cracks (from the window’s corners mainly), in which crack growth direction was not determined by masonry joints.The authors would like to acknowledge Mapei Spain S.A. for the materials supplied in this research. This research was funded by Spanish Ministry of Economy and Competitiveness, grant number BIA2015-69952-R and Spanish Ministry of Science, Innovation and Universities, grant number RTI2018-101148-B-I00

Seismic behavior of 1960's RC buildings exposed to marine environment

Steel rebars corrosion is one of the most important problems of reinforced concrete (RC) structures. The mechanical performance loss of RC elements because of steel corrosion can be aggravated under horizontal loads (e.g. wind pressure or seismic actions). This paper presents a methodology for the study of the seismic behavior of a residential typology of the Mediterranean coast, which was widely spread during the 1960's. These RC frame structures are usually 10 to 15 stories high, located very close to the coast and are exempt buildings, which made them specially exposed to chloride corrosion. Besides, there are some design conditions that should be taken into account: (i) these structures were designed only under gravity loads, especially seismic actions were not considered. (ii) The raw materials had lower quality than those considered in current design codes, e.g. structural concrete strength was around 15 MPa, and made with natural beach sand as fine aggregates (hence including chlorides into the concrete mass). Therefore, two important aspects converge in these buildings, fifty years of marine exposure (i.e. degradation by corrosion) and the omission of the seismic loads in the original design, making them especially vulnerable to earthquakes (in an area with a moderate-high seismicity). Hence, a methodology for the seismic analysis of the corroded structure is proposed, in order to determine the structural safety factor of this type of structures, and evaluate the effectiveness of a retrofitting if necessary

Experimental analysis of the loss of bond between rebars and concrete exposed to high temperatures

En el conjunto de materiales de construcción habituales en la edificación y las obras de ingeniería, el hormigón destaca entre otras razones por su excelente comportamiento frente a las altas temperaturas y la exposición al fuego. El presente estudio se centra en la adherencia residual entre el hormigón y las barras de acero corrugado soldable tras exponer probetas a altas temperaturas y enfriarlas hasta temperatura ambiente por convección natural. El estudio incluye hormigones de resistencia convencional, hormigones de alta resistencia y hormigones reforzados con fibras de polipropileno y fibras de acero. La adherencia hormigón-acero se ha medido mediante el conocido ensayo de pull-out. La campaña experimental también ha incluido la resistencia a compresión y la resistencia a tracción indirecta. Parte de las probetas se han ensayado a 28 días de edad a temperatura ambiente. A 60 días de edad se han repetido los ensayos a temperatura ambiente y se han realizado esos mismos ensayos en probetas calentadas en un horno industrial hasta tres rangos de temperatura: 450°C, 650°C y 825°C. Previo al proceso de calentamiento han sido sometidas durante 3 horas a un escalón de secado a 120°C. Mediante la metodología propuesta ha sido posible caracterizar la evolución de la pérdida de adherencia residual entre el acero y el hormigón conforme se exponen los especímenes a temperaturas más elevadas. La adición de fibras no tiene una influencia clara en la adherencia a temperatura ambiente. Sin embargo, sí se ha conseguido determinar una mejora sustancial de la adherencia residual en los hormigones, reforzados con fibras de acero sometidos a altas temperaturas.Within the context of the most usual construction materials for building and civil infrastructures, concrete stands out because of its excellent behaviour when exposed to high temperatures and fire condition. The present study focuses on the residual bond strength between concrete and steel rebars after exposure to elevated temperatures and natural cooling to room temperature. Normal strength and high strength concretes have been tested, as well as polypropylene and steel fibre reinforced concretes. The bond strength has been measured using the pull-out test. Compressive and tensile strength have also been determined. Some specimens have been tested at an age of 28 days and at room temperature. At 60 days the tests have been repeated at room temperature and after heating up to three temperature ranges: 450°C, 650°C and 825°C. Before each of the three heating phases, the specimens were pre-heated during 3 hours at 120 °C. After these experiments it has been possible to assess the loss of steel-concrete bonding for higher temperatures. The addition of fibres has no clear influence on the bonding at ambient condition. However, an improvement on the residual bonding strength has been observed for steel fibre reinforced concrete under high temperatures

Secure direct communication using Einstein-Podolsky-Rosen pairs and teleportation

A novel scheme for secure direct communication between Alice and Bob is proposed, where there is no need for establishing a shared secret key. The communication is based on Einstein-Podolsky-Rosen pairs and teleportation between Alice and Bob. After insuring the security of the quantum channel (EPR pairs), Bob encodes the secret message directly on a sequence of particle states and transmits them to Alice by teleportation. In this scheme teleportation transmits Bob's message without revealing any information to a potential eavesdropper. Alice can read out the encoded messages directly by the measurement on her qubits. Because there is not a transmission of the qubit which carry the secret message between Alice and Bob, it is completely secure for direct secret communication if perfect quantum channel is used

Textile Reinforced Mortars (TRM) tensile behavior after high temperature exposure

Although one of the main advantages of Textile Reinforced Mortars (TRM) is their non-combustible character, their behavior against fire or high temperatures has not been sufficiently studied at present. This work analyzes the behavior of different commercial systems containing inorganic mortars and fabric reinforcements based on glass, carbon and basalt fibers, subjected to different temperature levels. To characterize the mechanical response of the different systems, non-destructive tests have been carried out to determine the dynamic modulus of elasticity of the different materials, and subsequent destructive tests to determine their strength and stress-strain relationship. For this purpose, the TRM coupons have been subjected to uniaxial tensile tests and the deformations have been monitored using LVDT (Linear Variable Displacement Transducer) sensors and DIC (Digital Image Correlation), in order to evaluate cracking patterns and failure modes. The results show, in general terms, that the mechanical capacity of these materials is seriously compromised at temperatures in the order of 400 to 600 °C, which can easily be reached during a fire inside a building. Therefore, it can be concluded that although these systems are erroneously perceived as fire resistant in many cases, they may require additional protection depending on the specific use for which they are intended.The authors would like to acknowledge Mapei Spain S.A. for the materials supplied in this work. This research has been funded by the Spanish Ministry of Science, Innovation and Universities, grant number RTI2018-101148-B-100

SPIRAL facility at GANIL : ion beam simulation and optimisation method for the CIME cyclotron injection system

International audienc

Adaptación de la docencia en el cálculo de estructuras a las nuevas tecnologías

La implantación de las nuevas metodologías de enseñanza a partir de las directrices establecidas en el Espacio Europeo de Educación Superior, ha supuesto una renovación necesaria en los materiales docentes utilizados. En este sentido, el presente artículo muestra los avances en el uso de programas informáticos para la resolución de estructuras desarrollado a lo largo de las diferentes asignaturas que conforman las titulaciones de Ingeniería Civil, el Máster de Caminos, Canales, y Puertos, así como el Máster de Ingeniería de los Materiales, Agua y Terreno de la Universidad de Alicante. De esta forma el alumno es capaz de aproximarse a la realidad laboral, pudiendo comparar los resultados analíticos resueltos de forma tradicional, con los obtenidos con software comerciales ampliamente extendidos en el campo profesional. El uso de dichas herramientas se ha introducido de forma progresiva a lo largo de todos los cursos de las titulaciones anteriormente comentadas. Inicialmente, el alumno se familiariza con la resolución de estructuras a través de elementos barra, combinando diferentes materiales y acciones. Finalmente, el alumno desarrolla elementos placa, así como modelos reológicos y análisis dinámicos de estructuras. Por este motivo, y con el fin de completar la educación de los alumnos, en el presente trabajo se ha tratado de aproximar al alumno a las estructuras reales y a su posterior modelización numérica

Seismic Behavior of a Masonry Chimney Retrofitted with Composite Materials: A Preliminary Aproach

This paper presents a structural analysis of a masonry chimney, which is being catalogued as local interest heritage, according Eurocode 8. The chimney, located in Alicante (Spain), is severely damaged, and it shows several longitudinal cracks, and mortar loss between bricks. In order to guarantee the structural safety under seismic forces, the chimney was retrofitted with composite materials. This reinforcement comprised an internal textile reinforced mortar (TRM) layer, i.e. glass fiber mesh and cement matrix, and local reinforcement with longitudinal carbon fiber bands. This study consisted of two stages: first, numerical and experimental analyses of the original chim- ney were done. Second, design of an internal reinforcement scheme was done. The experimental text includes acceleration measures under ambient vibration for an operational modal analysis. And laboratory test for bricks and mortar to study the mineralogical composition and mechanical properties. The numerical analysis includes, preliminary pushover analysis before and after the reinforcement was done, and second, linear response spectrum analysis to evaluate the structural stability under the seismic demand.The authors express deep gratitude to Ministerio de Economia y Competitividad of the Spain’s Government and MAPEI. This work was financed by them by means of the BIA2015-69952R research Project

Coordinación vertical de la formación en Cálculo de Estructuras dentro del Grado en Ingeniería Civil: Desarrollo de aplicaciones interactivas para la docencia

Las nuevas tecnologías aplicadas a la enseñanza permiten la visualización de fenómenos físicos y su relación con la base matemática utilizada en la modelización de los mismos. En este trabajo se ha utilizado el programa Mathematica para realizar aplicaciones ilustrativas de distintos conceptos básicos para el cálculo de estructuras de ingeniería civil y edificación. Se han tratado temas como la reología, la plastificación de los materiales, la relación entre tensiones y deformaciones de los sólidos elásticos o la dinámica estructural, siempre desde un punto de vista teórico-práctico y tratando de mantener en todo momento un carácter interactivo que permita la participación activa de los estudiantes. Cada aplicación compagina los fundamentos teóricos y la influencia de los parámetros implicados, con la visualización en forma de gráfico animado de la función resultante