An effective thickness to estimate stresses in laminated glass beams under dynamic loadings

Finite element models for estimating stresses and displacements in laminated glass elements under dynamic loadings are very time-consuming because (1) many small 3D elements are needed to model accurately all the layers of the sandwich element and (2) the core usually shows a time and temperature dependent behaviour. In the last years, the concept of effective thickness using a quasi-elastic solution has got the attention of the research community because of its simplicity and reasonable level of accuracy achieved in the calculation of laminated glass elements under static loadings. In this paper, a dynamic effective thickness to estimate stresses in laminated glass beams under dynamic loadings in the frequency domain is derived using the correspondence principle. The analytical equations are validated by experimental tests carried out on simply supported and free–free laminated glass beams at different temperatures in the range 20–40 °

Natural frequencies and damping ratios of multi-layered laminated glass beams using a dynamic effective thickness

Multi-layered laminated glass panels are those with at least three monolithic glass layers and two viscoelastic interlayers. Multi-layered laminated glass panels are commonly used in floors, roofs and other horizontal glazing accessible to the public where a high level of security is required. Although the glass can be consider a linear-elastic material, the viscoelastic interlayers determine a non-linear behaviour of the laminated structure that must be taken into consideration. In this paper, an analytical model based on the effective thickness concept and the Ross, Kerwin and Ungar model is proposed to predict the dynamic behaviour of multi-layered laminated glass beam-like structures with different boundary conditions and at different temperatures. This analytical model allows the simplification of the calculus on this multi-layered laminated components opposite to use time-consuming numeric models. In this work, a study was carried out on a multi-layered laminated glass beam composed of three annealed glass layers and two polymeric interlayers. The analytical predictions are validated by numerical simulations and experimentally using operational modal analysis tests. The proposed model predicts the natural frequencies with errors less than 5% whereas the discrepancies in damping ratios are less than 50%

Dynamic effective thickness in laminated-glass beams and plates

In recent years, several equations have been proposed to calculate deflections and stresses in laminated-glass beams and plates under static loading using the concept of effective thickness, which consists of calculating the thickness of a monolithic element with equivalent bending properties to a laminated element. Recently, an effective thickness for the dynamic behavior of laminated-glass beams has been proposed to enable the modal parameters (natural frequencies, loss factors and mode shapes) to be determined using an equivalent monolithic model. In the present paper, the technique has been extended to the two-dimensional case of rectangular laminated-glass plates and the steps needed to estimate the modal parameters of laminated-glass elements using this methodology are presented. The dynamic effective thickness concept has been validated by experimental tests made on a laminated-glass beam and a laminated-glass plate. The results show that good accuracy is achieved in the natural frequencies and mode shapes but high scatter is encountered in the loss factor

Scaling Factor Estimation Using an Optimized Mass Change Strategy, Part 1: Theory

In natural input modal analysis, only un-scaled mode shapes can be obtained. The mass change method is, in many cases, the simplest way to estimate the scaling factors, which involves repeated modal testing after changing the mass in different points of the structure where the mode shapes are known. The scaling factors are determined using the natural frequencies and mode shapes of both the modified and the unmodified structure. However, the uncertainty on the scaling factor estimation depends on the modal analysis and the mass change strategy (number, magnitude and location of the masses) used to modify the dynamic behavior of the structure. In this paper, a procedure to optimize the mass change strategy is proposed, which uses the modal parameters (natural frequencies and mode shapes) of the original structure as the basic informatio

The effective-thickness concept in laminated-glass elements under static loading

Laminated glass is a sandwich element consisting of two or more glass sheets, with one or more interlayers of a polymer such as polyvinyl butyral (PVB). The static response of sandwich elements such as laminated-glass beams and plates can be modeled using analytical or numerical models in which the glass is usually modeled as linear-elastic and the PVB as linear-viscoelastic material, respectively. As a way to simplify the laminated-glass calculations, the concept of effective thickness has been recently proposed, which allows the calculation of laminated-glass beams as monolithic beams using an apparent or effective thickness. In this work, equations for the effective thickness of laminated-glass beams are derived from the analytical model proposed by Koutsawa and Daya and the results provided by this model are compared with the models of Bennison et al. and Galuppi and Royer-Carfagni. Finally, some static experimental tests were performed on several laminated-glass beams under distributed loading in order to validate the predictions of the model

Scaling Factor Estimation Using Optimized Mass Change Strategy, Part 2: Experimental Results

The mass change method is used to estimate the scaling factors, the uncertainty is reduced when, for each mode, the frequency shift is maximized and the changes in the mode shapes are minimized, which in turn, depends on the mass change strategy chosen to modify the dynamic behavior of the structure. On the other hand, the aforementioned objectives are difficult to achieve for all modes simultaneously. Thus, a study of the number, magnitude and location of the masses must be performed previously to the modal tests. In this paper, the mass change method was applied to estimate the scaling factors of a steel cantilever beam. The effect of the mass change strategy was experimentally studied by performing several modal tests in which the magnitude, the location and the number of the attached masses were change

Valuation of the flood protection service provided by coastal ecosystems

RESUMEN: Los ecosistemas costeros, tales como los arrecifes de coral o los manglares, son un recurso natural que protege el frente litoral de las inundaciones y evita pérdidas humanas y económicas. Sin embargo, están desapareciendo parte de estos ecosistemas debido a la sobreexplotación humana y al cambio climático. El deterioro ecosistémico, unido al crecimiento demográfico y económico costero, la subida del nivel del mar y la exposición directa a amenazas climáticas supone un escenario de riesgo futuro en el que los recursos naturales jugarán un papel cada vez más relevante. En esta tesis se propone una metodología multidisciplinar, probabilística y basada en procesos para valorar el servicio de protección frente a la inundación de los ecosistemas costeros. La aplicación de esta metodología a los de arrecifes de coral y manglares estima que la pérdida de estos ecosistemas incrementaría entre un 9% y 90% las pérdidas económicas por inundación y entre un 28% y un 80% el número de personas afectadas cada año. Indonesia, Filipinas, Cuba o México son algunos de los países que mayor beneficio de protección reciben de estos ecosistemas. Con este trabajo se pretende priorizar zonas de actuación e incentivar la conservación del medio ambiente para asegurar la disponibilidad de recursos naturales en el futuro.ABSTRACT: Coastal ecosystems, such as coral reefs and mangroves, are natural defences against coastal flooding by avoiding human and economic losses. However, these ecosystems are disappearing due to human activities and climate change. Ecosystem degradation, coastal settlement growth, sea level rise and the direct exposure of coastal areas to climate hazards are future risky scenarios in which natural resources will play an important role. This thesis develop a multidisciplinary, probabilistic and process-based methodology for valuing flood protection service provided by coastal ecosystems. The application of the methodology to coral reefs and mangroves estimates that ecosystem degradation would induce an increment between 9% and 90% the economic losses and between 28% and 80% the population affected by coastal flooding every year. Indonesia, the Philippines, Cuba or Mexico are some of the most protected countries. This work aims to prioritize nature-based development plans and to encourage environmental conservation activities that ensure future ecosystem benefit flux.Quiero agradecer al Ministerio de Ciencia Innovación y Universidades por la financiación recibida por medio de la beca de Formación de Personal Universitario (FPI, BES-2015-074343) , asociada al proyecto del Plan Nacional ECOPROOF (BIA2014-59718-R), así como al IH Cantabria y a la Universidad de Cantabria por proporcionarme los recursos necesarios para el desarrollo de esta Tesis

Interest and activities to introduce the pupils of primary school to microscopic living beings.

RESUMEN El presente trabajo tiene como objetivo clarificar si es de gran interés o por el contrario carece de relevancia introducir en alumnado de Educación Infantil Y Primara el mundo de los seres microscópicos. Para dar una respuesta que sea verídica y fiable se han utilizado los resultados obtenidos en unas hojas de observación, extraídas tras la realización de diversas actividades utilizando diferentes aparatos de microscopía con alumnos de diversos cursos de Educación Primaria de centros de la región de Cantabria. Todo ello se ha corroborado y apoyado con la información obtenida de la búsqueda bibliográfica en fuentes académicas y técnicas que han incluido documentos relacionados tanto con la enseñanza como con la importancia del conocimiento sobre aquellos pequeños organismos que pueden ser perjudiciales para la salud.ABSTRACT The aim of this work is to clarify whether it is of great interest or, on the contrary, irrelevant to introduce the world of microscopic beings to infant and primary school pupils. To give a truthful and reliable answer, the results obtained from observation sheets have been used, extracted after carrying out various activities using different microscopy apparatus with pupils from different Primary Education classes in schools in the region of Cantabria. This has been corroborated and supported by the information obtained from the bibliographic search in academic and technical sources that have included documents related both to teaching and to the importance of knowledge about those small organisms that can be harmful to health.Grado en Magisterio en Educación Primari