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Cuiabá, Brazil

Goncalves R.,UNIC | Ritto-Correa M.,University of Lisbon | Camotim D.,University of Lisbon
Computational Mechanics | Year: 2010

This paper presents a new and general approach for the calculation of cross-section deformation modes in thin-walled beams, to be used in the framework of generalized beam theory (GBT). The proposed approach subdivides and hierarchizes the cross-section deformation modes by employing several kinematic hypotheses. This makes it possible to discard a priori specific types of deformation modes and consequently reduce the number of cross-section degrees-of-freedom. The approach is applicable to arbitrary (with open and closed parts) polygonal cross-sections with external and internal constraints and allows for the a posteriori inclusion of particular deformation modes (e.g., shear deformation modes in a part of the cross-section). Although only GBT applications are dealtwith, the deformationmodes obtained may be straightforwardly incorporated in other thinwalled beam formulations that include cross-section deformation. © Springer-Verlag 2010. Source

Jacinto L.,Polytechnic Institute of Lisbon | Pipa M.,National Laboratory for Civil Engineering | Neves L.A.C.,UNIC | Santos L.O.,National Laboratory for Civil Engineering
Construction and Building Materials | Year: 2012

This study focus on the probabilistic modelling of mechanical properties of prestressing strands based on data collected from tensile tests carried out in Laboratório Nacional de Engenharia Civil (LNEC), Portugal, for certification purposes, and covers a period of about 9 years of production. The strands studied were produced by six manufacturers from four countries, namely Portugal, Spain, Italy and Thailand. Variability of the most important mechanical properties is examined and the results are compared with the recommendations of the Probabilistic Model Code, as well as the Eurocodes and earlier studies. The obtained results show a very low variability which, of course, benefits structural safety. Based on those results, probabilistic models for the most important mechanical properties of prestressing strands are proposed. © 2012 Elsevier Ltd. All rights reserved. Source

Transversal vibrations induced by a load moving at a constant speed along a finite or an infinite beam resting on a piece-wise homogeneous visco-elastic foundation are studied. Special attention is paid to the amplification of the vibrations which arise as the point load traverses a foundation discontinuity. The governing equations of the problem are solved by the normal-mode analysis. The solution is expressed in the form of an infinite sum of orthogonal natural modes multiplied by the generalized displacements. The natural frequencies are obtained numerically exploiting the concept of the global dynamic stiffness matrix. This ensures that the frequencies obtained are accurate. The methodology is neither restricted by load velocity nor damping and is simple to use, though obtaining the numerical expression of the results is not straightforward. A general procedure for numerical implementation is presented and verified. There is no restriction for finite structures, however, for infinite structures, validity of the results is restricted to a "region of interest" of finite length. To illustrate the methodology, the probability of exceeding an admissible upward displacement is determined when the load travels at a certain velocity according to the normal distribution. In this problem, the given structure has an intermediate part of adaptable foundation stiffness, which is optimized in a parametric way, enabling to draw important conclusions about the optimum intermediate stiffness. The results obtained have direct application on the analysis of railway track vibrations induced by high-speed trains crossing regions with significantly different foundation stiffness. © 2010 Elsevier Ltd. All rights reserved. Source

V. Faria D.M.,Ecole Polytechnique Federale de Lausanne | Einpaul J.,Ecole Polytechnique Federale de Lausanne | P. Ramos A.M.,UNIC | Fernandez Ruiz M.,Ecole Polytechnique Federale de Lausanne | Muttoni A.,Ecole Polytechnique Federale de Lausanne
Construction and Building Materials | Year: 2014

One possibility for strengthening existing flat slabs consists on gluing fibre reinforced polymers (FRPs) at the concrete surface. When applied on top of slab-column connections, this technique allows increasing the flexural stiffness and strength of the slab as well as its punching strength. Nevertheless, the higher punching strength is associated to a reduction on the deformation capacity of the slab-column connection, which can be detrimental for the overall behaviour of the structure (leading to a more brittle behaviour of the system). Design approaches for this strengthening technique are usually based on empirical formulas calibrated on the basis of the tests performed on isolated test specimens. However, some significant topics as the reduction on the deformation capacity or the influence of the whole slab (accounting for the reinforcement at mid-span) on the efficiency of the strengthening are neglected. In this paper, a critical review of this technique for strengthening against punching shear is investigated on the basis of the physical model proposed by the Critical Shear Crack Theory (CSCT). This approach allows taking into account the amount, layout and mechanical behaviour of the bonded FRP's in a consistent manner to estimate the punching strength and deformation capacity of strengthened slabs. The approach is first used to predict the punching strength of available test data, showing a good agreement. Then, it is applied in order to investigate strengthened continuous slabs, considering moment redistribution after concrete cracking and reinforcement yielding. This latter study provides valuable information regarding the differences between the behaviour of isolated test specimens and real strengthened flat slabs. The results show that empirical formulas calibrated on isolated specimens may overestimate the actual performance of FRP's strengthening. Finally, taking advantage of the physical model of the CSCT, the effect of the construction sequence on the punching shear strength is also evaluated, revealing the role of this issue which is also neglected in most empirical approaches. © 2014 Elsevier Ltd. All rights reserved. Source

Unic | Date: 2012-12-25

Coffee grinders, other than hand operated, namely, electric and power-operated; electric emulsifying machines for percolators and cappuccino and coffee machines; dishwashers; glass washing machines. Apparatus for production of steam, namely, steam generators; steam accumulators; steam boilers other than parts of machines; hot air apparatus, namely, hot air blowers, electric hot air hand dryers, and hot-air space heating apparatus; electric coffee percolators; electric coffee machines; electric percolators and coffee makers with hot water and steam production; tips for percolators and coffee and cappuccino machines; coffee makers excluding coffee grinders; electric coffee filters, not of paper being part of electric coffee makers; coffee roasters; electric kettles; electric espresso coffee machines; machine for preparing beverages by infusion or by solubilization, namely, electric drink preparation machines. Non-electric percolators and non-electric coffee makers; non-electric percolators and coffee makers that use of hot water and steam; coffee pots, all these products being non electric and not of precious metals; hand operated coffee grinders; non-electric coffee filters, not of precious metals, not of paper being part of non-electric coffee makers; glasses for drinking; cups, not of precious metal; basins of precious metal; table plates, not of precious metal; saucers, not of precious metal; sugar bowls, not of precious metal; coffee services, not of precious metal; tea infusers of non-precious metal, tea caddies, not of precious metal; tea strainers, not of precious metal; tea services, not of precious metal; teapots, not of precious metal; tea-strainers, not of precious metal; non-electric kettles.

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