Indirect assessment of the contribution of NSM CFRP laminates for the shear strengthening of RC beams

Near Surface Mounted (NSM) strengthening technique has received increasing attention within the scientific and technical communities due to the positive indicators that this technique can provide in terms of strengthening performance. The NSM is especially effective for the shear strengthening of RC beams due to the ease of its application and the possibility of installing the Fibre Reinforced Polymer (FRP) elements in the most appropriate locations for the optimization of their contribution in terms of shear resistance. Furthermore, the FRP elements are protected against acts of vandalism and do not change the geometric configuration of the strengthened components since they are installed into thin slits opened on the concrete cover. Although either circular or rectangular FRP bars are used, recent research shows that the latter (herein designated as laminates) are more effective and easier to install. Research carried out in the area of NSM for the shear strengthening of RC beams reveals that the percentage, inclination and spacing of FRP laminates have a considerable influence on the effectiveness of this technique. The percentage of existent internal stirrups, the relative position of stirrups and FRP laminates and concrete strength class are also important aspects for the performance of the NSM technique. To estimate the influence of these parameters, a new test setup is proposed and an experimental program has been planned. The test setup is similar to the indirect tensile test (Brazilian test). The experimental program consists of 27 cylindrical concrete specimens of 180 mm thickness and 600 mm diameter, grouped in series for evaluating the influence of the aforementioned parameters. The test setup is detailed, and the results of the first series are presented and discussed.Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ECM/59033/2004

Elementos de casca em alvenaria cerâmica reforçados com laminados de fibras de carbono

Este trabalho refere-se a um estudo experimental efectuado sobre elementos de casca em alvenaria cerâmica com juntas e camada de compressão em betão simples, reforçados com laminados de CFRP para esforços de flexão. No reforço utilizaram-se duas técnicas: laminados colados sobre a superfície do betão das juntas; laminados inseridos em entalhes executados no betão das juntas. Os resultados obtidos demonstram a eficiência das técnicas de reforço utilizadas, dado se ter registado um substancial aumento da capacidade resistente e das condições de segurança dos elementos ensaiados.Shell elements made by ceramic units bonded by concrete joints and covered by a concrete compression layer were strengthening by strips of carbon fiber reinforced polymer laminates (CFRP), using two reinforcing techniques: CFRP laminates externally bonded to concrete joints, CFRP laminates bonded into slits made on the concrete joints. Both reinforcing techniques have shown to be effective in terms of increasing the ultimate load and its corresponding deformability, but the last one was more effectiveness. In the present work the experimental research is described and the main results are presented and discussed

Composite materials for the structural strengthening of reinforced masonry shells

Since the 1950s, the Uruguayan engineer Eladio Dieste designed curved lightweight masonry shells of impressive span width, complex shape and high attractiveness. This structural system is composed of a top mortar cover, a layer of clay bricks, mortar joints, and steel reinforcement. For the permanent loads, this structural system has been working satisfactory, in spite of rebar corrosion being detected in some shells. However, if submitted to an earthquake of considerable magnitude, damage can be significant, and its rupture can even occur. In the present paper, an effective strengthening technique, using carbon fibre reinforced polymer (CFRP) materials, was developed to significantly increase the ultimate load of damaged reinforced masonry shell structures. This strengthening system is composed by strips of wet lay-up CFRP sheet and prefabricated CFRP laminates. The sheet strips are bonded, with epoxy resin, to the top cracked concrete surface of the shell to increase its flexural resistance for the negative bending moments, while laminates are fixed, with epoxy adhesive, to the bottom of the reinforced concrete joints to increase the shell flexural resistance for the positive bending moments. This strengthening system was applied to a damaged shell, having resulted a significant increase in the service load and an increase of about 76% in the ultimate load. A monitoring system was installed to evaluate the applied force, the deflection in critical sections and the strains in the composite materials and in the steel reinforcement. The experimental research is described and the main results are presented and discussed

Shear testing of stacked bonded masonry

Report 02-DEC/E-10 - draft versio

Liquid crystal phase and waterlike anomalies in a core-softened shoulder-dumbbells system

Using molecular dynamics we investigate the thermodynamics, dynamics and structure of 250 diatomic molecules interacting by a core-softened potential. This system exhibits thermodynamics, dynamics and structural anomalies: a maximum in density-temperature plane at constante pressure and maximum and minimum points in the diffusivity and translational order parameter against density at constant temperature. Starting with very dense systems and decreasing density the mobility at low temperatures first increases, reach a maximum, then decreases, reach a minimum and finally increases. In the pressure-temperature phase diagram the line of maximum translational order parameter is located outside the line of diffusivity extrema that is enclosing the temperature of maximum density line. We compare our results with the monomeric system showing that the anisotropy due to the dumbbell leads to a much larger solid phase and to the appearance of a liquid crystal phase. the double ranged thermodynamic and dynamic anomalies.Comment: 14 pages, 5 figure

Testing, analysis and building technology for industrialized reinforced masonry shells

This paper addresses briefly the research carried out at University of Minho, regarding an industrialized solution for reinforced masonry shells. The aspects of material characterization are presented, together with a contribution for a full prefabrication process. Aspects related to numerical analysis and structural design can be found in [1-3].comissão Europeia - projeto GROWTH, GROW-1999-70420 “ISOBRICK”Fundação para a Ciência e a Tecnologia (FCT

Soluções industrializadas para cascas de betão com elementos cerâmicos incorporados

A presente comunicação apresenta resultados de um projecto em curso, tendo em vista definir uma solução competitiva para cascas de betão armado com elementos cerâmicos incorporados. As soluções tecnológicas consideradas, que incluem pré-fabricação parcial e total são discutidas, os ensaios experimentais e os seus resultados analisados e os protótipos a serem construídos são apresentados. Os resultados já obtidos salientam as potencialidades da préfabricação parcial e do bom desempenho da solução proposta

Painéis de alvenaria cerâmica com juntas de concreto submetidos a ensaio de cisalhamento

É notável que o mercado da construção civil encontra-se cada vez mais esclarecido e a concorrência acaba tornando-se um fator estimulante para a área de pesquisa de novas tecnologias. É nesse contexto que a alvenaria cerâmica está inserida, trazendo uma nova perspectiva sobre a sua utilização nas contruções, uma vez que tem sido reconhecida como elemento de elevada capacidade estrutural. O trabalho apresentado neste documento, trata da apresentação e análise de resultados do comportamento de painéis de alvenaria de cerâmica furada, ligada por juntas de concreto, ensaiados ao cisalhamento, segundo a Norma Européia EN1052-4. Os ensaios presentes neste estudo fazem parte de um projeto no qual estão incluídos uma série de ensaios para a caracterização mecânica de materiais que serão utilizados, posteriormente, na confecção de coberturas em cascas de alvenaria armada