Detección de daño en estructuras mediante la aplicación de la transformada Wavelet a su deflexión estática

CNIM 2010 : Ciudad Real, 3-5 noviembre 2010. Anales de ingeniería mecánica, 2010, 18En los últimos años ha existido un creciente interés en desarrollar nuevas metodologías que permitan la detección de daño en estructuras. La mayoría de estos métodos se basan en la caracterización de la respuesta dinámica de las estructuras, pero también existen metodologías basadas en su respuesta estática. Una de las ventajas de los métodos estáticos es su facilidad de realización y la posibilidad de reducir fácilmente el número de sensores necesarios gracias a la repetitividad de los ensayos. Esto hace que puedan resultar de interés en determinadas aplicaciones, y complementar las ventajas que ofrecen a su vez los métodos dinámicos. Dentro de la detección de daño en estructuras, la transformada wavelet aparece como una herramienta útil para detectar variaciones en la misma. En los ensayos estáticos, se puede utilizar para analizar la deformada estática de la estructura y detectar posibles cambios producidos por la presencia de un daño. En el presente artículo se aplica la transformada wavelet a la respuesta estática de una viga biapoyada obtenida a partir de un modelo numérico de elementos finitos. La metodología implementada supone la obtención de la respuesta para una carga puntual ubicada en distintas posiciones, analizándose la superposición de los resultados obtenidos a partir de cada estado de carga. Se analizan los resultados para distintas ubicaciones del daño, niveles de carga y número de puntos de medida. Aplicando una wavelet tipo Haar, se estudia la evolución de los coeficientes y el producto de éstos por su función wavelet correspondientes a un nivel de escala 1. A partir de los resultados obtenidos, se caracteriza el efecto de la presencia de una grieta y se analiza la capacidad del método para la detección del dañ

Damage localization and quantification in simply supported beams using static test data

Artic. 012007 12th International Conference on Damage Assessment of StructuresA novel simple method using static test data for damage detection, localization, and quantification in beams is presented in this paper. The method is based on the change of the deflections of the beam between a reference and a damaged state. For simply supported beams with a single damage, the maximum value of the change of deflections indicates the location of damage. Once the damage is located, one could estimate the rotational stiffness at the damaged cross section by applying a superposition scheme to isolate the effect of damage and by using basic structural analysis equilibrium equations. Afterwards, damage extent is evaluated through an existing relation between rotational stiffness and damage severity. Several static tests of a simply supported steel beam with a point load at different locations were conducted to exam the performance of the strategy. The damage is artificially introduced as an opened crack located at the bottom of the beam. The deflections of the beam were measured by using a Digital Image Correlation system. The results show that the method can accurately detect and quantify the damage. The method is non-model based and can be easily conducted. No specific loading positions are required and damage identification objective can be achieved from just one single static test.Junta de Andalucía P12-TEP-254

Continuous wavelet analysis of mode shapes differences for damage detection

This paper presents a new damage detection methodology for beams. It applies wavelet analysis to locate the damage from changes in the mode shapes (geometric based analysis). The proposed methodology requires the mode shapes of a reference undamaged state as well as those of the potentially damaged one. Once obtained, a continuous wavelet transform is applied to the difference of the mode shape vectors to obtain information of the changes in each of them. Finally, the results for each mode are added up to compute an overall result along the structure. For the addition, the wavelet coefficients of each mode are weighted according to the corresponding variation of the natural frequency. By doing so, emphasis is given on those modes that are more likely to be affected by damage. On the other hand, mode shapes that have not changed their natural frequencies are disregarded. The proposed methodology also includes mathematical techniques to avoid wavelet transform edge effect, experimental noise reduction in mode shapes and creation of new virtual measuring points. It has been validated by experimental analysis of steel beams with cracks of different sizes and at different locations. The results show that the method is sensitive to little damage. The paper analyses the severity threshold of damage and the required number of sensors to obtain successful results.Ministerio de Economía y Competitividad BIA2010-1484

Estudio del comportamiento mecánico para la recuperación de una escultura histórica

XV Congreso Nacional de Ingeniería Mecánica, celebrado en Cádiz en 2002En este artículo se presenta parte del trabajo desarrollado para la recuperación de una escultura histórica ( El Giraldillo) desde un punto de vista mecánico, dentro del proyecto de restauración integral de dicha obra de arte. Esta escultura corona la torre de la Catedral de Sevilla, La Giralda, desde el año 1568, haciendo la función de veleta. Resulta por tanto fundamental analizar su comportamiento mecánico de cara a llevar a cabo una restauración tanto de la escultura propiamente dicha como de su estructura interna, que le permita soportar con garantías las distintas acciones mecánicas a las que se ve sometida. Para ello, se ha construido un modelo de elementos finitos de la Veleta, cuyo análisis, junto con el estudio de las huellas que el paso del tiempo ha ido dejando en ella, han servido para diseñar una nueva estructura interna que sustituya a la anterior, así como una serie de elementos internos que refuercen la escultura

Experimental validation of usual numerical models of cracked beams for damage detection approaches

Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.The performances of damage detection approaches are often tested by using numerical solutions of undamaged and damaged structures. However, the numerical results used for a preliminary analysis are useful as far as they can provide a good approach to real experimental results. This paper presents a collection of numerical results obtained from three different finite element models that are extensively used in the literature for the analysis of damage detection approaches, and compare them with experimental results. The paper considers beam, plate and solid models. Natural frequencies and mode shapes of the beams are analyzed. The results show that the results obtained with 1D models are not likely to be well related to a specific experimental test, whereas 2D and 3D models provide good results if the damage is a notch, but, the do not if it is a fatigue crack

PBL from Real Projects and Students Initiative: a case study

The benefits of Project Based Learning (PBL) to acquire technological knowledge as well as transversal skills by students are well known. However, the implementation of PBL requires additional efforts from teachers and students, as well as additional teaching resources when compared to traditional teaching. This paper presents a case study of a singular PBL experience developed within a subject entitled Experimental Structural Analysis. This subject had PBL already implemented. However, the paper describes a new PBL experience that was suggested by some students that were part of the Formula Student (FS) team from the University of Seville. 24 students and 2 teachers took part in this new experience. The proposed PBL introduced some new challenges in the subject. The paper describes how the subject was organized in terms of theoretical and practical lessons, tutorials and assessment (including the introduction of a novel Self Assessment Factor). The paper analyzes the results from an academic point of view and describes the benefits, difficulties, advantages and opportunities arising from a PBL approach in which students play a new role as real promoters of a real project. Results from academic scores, surveys from students and teachers' perceptions are analyzed. The percentage of students who ask the teachers of the subject to supervise their final degree project is used as a new satisfaction indicator from students. The paper shows that this PBLmethodolodogy is enriching and suitable for the learning process of most the students. However, new challenges arise such as encouraging all the students to be actually involved in the cooperative work and ensuring that the main theoretical concepts are learned. The FS competition is proven to be a good opportunity for implementing PBL based on a real project. © 2017 TEMPUS Publications.Junta de Andalucía P12-TEP-254

Implantación de nuevas metodologías docentes para el aprendizaje de técnicas experimentales aplicadas al análisis de estructuras

Trabajo reproducido y difundido en el repositorio idUS con permiso de la Asociación Española de Ingeniería Mecánica (AEIM)En este trabajo se presentan las metodologías docentes que se han implementado en los últimos cuatro años en la asignatura Análisis Experimental de Estructuras. La enseñanza de esta asignatura se ha basado en el aprendizaje basado en la realización de prácticas. Con ellas se pretende abarcar todos los aspectos que pueden encontrarse en el análisis experimental de estructuras: funcionamiento y manejo de transductores, sistemas de adquisición de datos, lenguajes de programación para la adquisición, diseño y puesta en marcha de ensayos, etc. El trabajo práctico se realiza en el laboratorio y sobre estructuras reales, y se invita a los alumnos a que asistan a pruebas de carga de grandes estructuras, y otros ensayos de campo. Aunque la mayor parte del trabajo es práctico, previamente a la realización de las prácticas se imparten una serie de clases donde se ilustran los conceptos teóricos. El material docente de la asignatura se encuentra disponible en Internet y actualmente se está elaborando una página Web interactiva que incluya un foro de discusión acerca de los temas que se tratan en la asignatura y que permitirá la realización de tutorías en línea.An application of new teaching techniques on Experimental Analysis of Structures is presented in this paper. Teaching is based on practice. Practical lessons are designed in order to cover ali the topics related with experimental analysis of structures: operation and use of sensors, data acquisition systems, programming languages for acquisition, design and start up of testing, etc. Practical lessons are carried out at laboratory or on real structures. Students are also invited to attend actual structural tests, including full scale testing. Although most of the work to be done by students is practical, there are sorne theoretic lessons before the practical ones. Teaching material is available on internet and a new website is being developed for this subject. Forums and on-line tutoring have been considered

Enseñanza de Teoría de Estructuras mediante el diseño, cálculo, construcción y ensayo de modelos

CNIM 2010 : Ciudad Real, 3-5 noviembre 2010. Anales de ingeniería mecánica, 2010, 18: 1-7Este trabajo presenta los resultados de una experiencia de innovación docente dentro de la docencia en el ámbito de las estructuras en la titulación de Ingeniería Industrial en la Universidad de Sevilla. La metodología docente aplicada pretende motivar al alumno al aprendizaje promoviendo el diseño, cálculo, construcción y ensayo de estructuras. De esta forma, el alumnado se forma no sólo como calculista, sino también desarrolla habilidades que le permiten comprender el funcionamiento de las estructuras. El proyecto abarca asignaturas impartidas en tercer y quinto curso de la titulación. En tercer curso, los estudiantes inician su formación estructural con la asignatura Teoría de Estructuras en la cual se les transmiten los fundamentos básicos mediante el diseño, fabricación y ensayo de estructuras de madera de balsa. Los alumnos disponen de programas informáticos para optimizar el diseño de sus modelos previamente a su construcción y posterior ensayo en el laboratorio. Tras esta primera aproximación a la Teoría de Estructuras, el alumno se forma en conceptos mas avanzados, como el comportamiento dinámico de las estructuras y las inestabilidades, en tipos estructurales particulares como son los casos de las placas y las estructuras laminares, y en materiales estructurales como el acero y el hormigón. Antes de finalizar sus estudios, el alumno se vuelve a encontrar con una metodología docente basada en el aprendizaje a través de proyectos en la asignatura Análisis Experimental de Estructuras. En este caso los proyectos que resuelve el alumno recorren parte de la casuística que se encontrará profesionalmente una vez egresado. Este trabajo presenta las ventajas de esta metodología desde el punto de vista de la enseñanza en ingeniería

Analysis of stationary roving mass effect for damage detection in beams using wavelet analysis of mode shapes

Publicado en Journal of Physics: Conference Series 628 (2015), 012014- . Ghent, Belgium : 24 – 26 August 2015One of the main challenges in damage detection techniques is sensitivity to damage. During the last years, a large number of papers have used wavelet analysis as a sensitive mathematical tool for identifying changes in mode shapes induced by damage. This paper analyzes the e ect of adding a mass to the structure at di erent positions. Depending on the location and severity of damage, the presence of the mass a ects the natural frequencies and mode shapes in a di erent way. The paper applies a damage detection methodology proposed by the authors, although it has been modi ed in order to consider the addition of the mas. This methodology is based on a wavelet analysis of the di erence of mode shapes of a damaged and a reference state. The singular behavior of a normalized weighted addition of wavelet coe cients is used as an indicator of damage. The presence of damage is detected by combining all the information provided by mode shapes and natural frequencies for di erent positions of the roving mass. A continuous wavelet transform is used to detect the di erence between the response of a healthy state and a damaged one. The paper shows the results obtained for a beam with di erent cracks. The paper analyzes the sensitivity to damage of the proposed methodology by considering some practical issues such as the size of the crack, the number of measuring points and the e ect of experimental noise

Monitoring the mechanical behaviour of the weather vanesculpture mounted atop Seville Cathedral’s Giralda Tower

This article presents the application of monitoring and detection of structural damage techniques to a historic monument. Seville cathedral’s famous bell tower ‘La Giralda’ is 96 m tall and is crowned with a large 16th century sculpture known as ‘Giraldillo’. The sculpture is supported with an internal bar structure, which is fitted over the axis about which it rotates according to the wind direction, allowing it to function as a weathervane. Between 1999 and 2005 the Giraldillo was demounted and underwent an intensive restoration process, which included mechanical and structural repair work. As the sculpture is only accessible by means of complex and costly scaffolding systems, an instrumentation system consisting of different types of sensors was installed to study the assembly’s mechanical response, its functioning as a weathervane and its state of conservation while it was being remounted atop the Giralda Tower. Different damage detection techniques aimed at detecting possible deterioration in the Giraldillo’s support structure were employed as well. This article presents results obtained in 2 years of system operation, showing how structural heath monitoring techniques can be applied to historical monuments