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Cardoso J.B.,University of Lisbon | Valido A.J.,Polytechnic Institute of Setubal
Computers and Structures

This paper aims to perform optimal design of cross-section properties of thin-walled laminated composite beams. These properties are expressed as integrals based on the cross-section geometry, on the warping functions for torsion, shear bending and shear warping, and on the individual stiffness of the laminates constituting the cross-section. The finite element method is used in discretizing the theory. For design sensitivity calculations, the cross-section is modelled throughout design elements. Geometrically, these elements may coincide with the laminates that constitute the cross-section. The developed formulation is based on the concept of adjoint structure. After a warping function is calculated for the cross-section, an adjoint problem may be formulated for each of the properties and a corresponding adjoint warping is determined. It can be applied in a unified way to open, closed or hybrid cross-sections. Design optimization is performed by nonlinear programming techniques. Laminate thickness and lamina orientations are considered as design variables. © 2010 Elsevier Ltd. All rights reserved. Source

Macedo P.,Polytechnic Institute of Setubal | Macedo P.,New University of Lisbon | Camarinha-Matos L.M.,New University of Lisbon
Computers and Industrial Engineering

Collaborative enterprises networks are composed of heterogeneous and autonomous enterprises, which are often geographically distributed. As such, it is natural that each enterprise has its own set of values and preferences and as a result, conflicts among partners might emerge due to some values misalignment. Therefore, tools to support the analysis of Value Systems and their alignment in a collaborative context are relevant to improve the network management. Since a Value System reflects the set of values and preferences of an actor, which are cognitive issues, a cognitive analysis approach based on fuzzy causal maps is introduced. A set of qualitative assessment methods are designed to properly capture and integrate multiple perspectives about the concept of Value Systems alignment, in order to improve the identification and assessment of Value Systems misalignments in the context of collaborative enterprises networks. A web based tool to support these qualitative models and methods in a integrated way is used in a case study. Finally, experimental results are presented and discussed. © 2012 Elsevier Ltd. All rights reserved. Source

Bras A.,Polytechnic Institute of Setubal | Henriques F.M.A.,New University of Lisbon
Construction and Building Materials

The goal of this research was to develop a methodology for grout composition optimization concerning specific applications. It could be developed for masonry consolidation or bonded prestressed tendon grout, pre-placed aggregate grout, among others. The grout development does not only depend on its intrinsic properties but also on the nature and features of the support. The purpose of a grout injection technique applied in a multiple leaf wall is to increase the compactness and create links between the internal and external leaves, which improve not only shear and flexural resistance but also the compressive strength. In practice, the variability of voids within masonries requires an ability to fine tune the rheological properties of the grout in order to optimally fill the voids. The methodology proposed here for testing grout injectability in a porous media like masonry is a logical tool to use in grout optimization. It shows that several grout parameters should be controlled for a successful injection. Concerning the support and its typology, the mortar between stones plays a fundamental role in the effectiveness of the intervention, due to its reduced porosity and composition. Besides that, earth and mortar, for example, can be present in the interior of masonry and make difficult, with their absorption, the injection. Thus, the water retention capacity of grout should be controlled to prevent that problem, as it was made in this work, using the optimized mixing procedure that takes into account that and other fresh grout properties. This study analyses some relevant grout properties such as yield stress, plastic viscosity, flowability and injectability for natural hydraulic lime based grouts in different porous media. The research shows that there are differences in the grout behaviour, especially in rheological properties, when different mixing procedures and/or grout composition (different water/binder or fly ash/binder ratios) are used and that fresh grout properties may be optimized for injection purpose. © 2011 Elsevier Ltd. All rights reserved. Source

Marques P.F.,Polytechnic Institute of Setubal | Marques P.F.,New University of Lisbon | Chastre C.,New University of Lisbon | Nunes A.,Secil SA
Cement and Concrete Composites

The presented work aims at studying the modelling of long term performance of concrete compositions with different proportions of clinker as regards the diffusion of CO2 in concrete-carbonation. The replacing constituents of clinker that will be part of the binder in each concrete composition are limestone filler and low calcium fly ash (FA). The used percentage of FA by weight of binder was of 50%. Concrete compositions were made following standard prescribed requirements to attain service lives of 50 and 100 years as regards concrete performance against reinforcing steel corrosion. Test results of compressive strength and carbonation depth are reported at different curing ages of 28, 90, 180 and 365 days. Carbonation results were used for the implementation of modelling equations in order to estimate the design service life regarding reinforcing steel corrosion. Two performance-based methods were used: safety factor method and probabilistic method, and their results compared with the traditional prescriptive approach. At the age of 28 days the composition with OPC is the only one that reaches the target periods of 50 or 100 years. For the probabilistic method, different curing age results were analysed. For the tested results at 90, 180 and 365 days of age the reliability of some of the compositions with blended cements is within the minimum required, although still far from the higher performance of concrete with OPC.© 2012 Elsevier Ltd. All rights reserved. Source

Neves R.,Polytechnic Institute of Setubal | Branco F.,University of Lisbon | De Brito J.,University of Lisbon
Cement and Concrete Composites

The relationship between natural and accelerated concrete carbonation resistance has been investigated. Cores were taken from real structures and their non-carbonated inner part was subjected to accelerated carbonation resistance testing, allowing the assessment of natural and accelerated carbonation resistance on the same specimen. The carbonation resistance was characterised by means of a coefficient given by the ratio between carbonation depth and the square root of exposure time. According to the literature on the subject a linear relationship between accelerated and natural carbonation coefficients, not influenced by cement type, was assumed. A complementary experimental study was carried out to investigate how age influences accelerated carbonation resistance. Different factors, according to exposure classes, were determined by linear regression analysis to correlate accelerated and natural carbonation coefficients. The use of these factors together with Fick's first law enables the long term prediction of carbonation depth in structures based on accelerated carbonation resistance testing. © 2013 Elsevier Ltd. All rights reserved. Source

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