1,721,102 research outputs found
Effect of earthquake statistically correlated vertical component on inelastic demand to regular reinforced-concrete frames
No full textPost-earthquake survey and structural analysis prove that the vertical seismic action can damage buildings and bridges, even those with regular configuration. Moreover, there is evidence that one principal axis of ground motion may be not vertical. The inelastic demand to regular building structures is assessed here considering both uncorrelated and cross-correlated random seismic components, concurrent to deterministic weight. The method is conventional statistical equivalent linearization. Planar reinforced-concrete frames are analyzed parametrically varying the number of stories, the design ductility class, or the foundation ground type, as well as variance and cross-covariance of the vertical seismic component. Following a lumped plasticity approach, the bending moment-rotation relationship is a Bouc-Wen equation extended for asymmetry and interaction with axial force. Based on mean values, variances, and percentiles of response, the effect of uncorrelated vertical excitation is appreciable only on stress resultants of little practical consequence. Much more important is the effect of cross-correlated vertical excitation. As extreme results, the interstory drift demand increases up to four times. The rotation ductility demand to columns, less than 2 under uncorrelated excitations, rises to 5, meaning very likely yielding of columns designed as strong. The probability of axial force in the columns being tensile grows from negligible value to 8%. The beams may yield also around mid-span. The frame plastic mechanism worsens towards soft story, the peak deformation ductility being demanded more than the cyclic ductility. Not only variance of the vertical ground motion, but also cross-covariance with the horizontal one should be considered in the near field
Life cycle assessment of sustainable concrete made with recycled aggregates
No full textThe results of an environmental study on concrete manufacture that follows the standard protocol of life cycle assessment are shown in this document. The study has been done for seven types of concrete: one conventional and six containing cement kiln dust (10%), marble sludge (10%) and demolition waste (10%, 80% and 100%) respectively, in partial or total substitution of natural aggregate. Six end of life scenarios have been proposed for the application of the life cycle assessment methodology. One of these is referred to the complete disposal of the waste obtained from demolition of studied concrete while in the others the treatment and recycling of demolition waste are analysed. In the latter cases the treatment plant location has been considered at different distances from the demolition site. The results show that, the life cycle of the considered concrete mainly impacts on greenhouse, summer pollution and winter pollution effects
Calibrazione dei coefficienti di "capaciry design" per i telai in c.a. mediante linearizzazione stocastica.
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The association scheme on the set of flags of a finite generalized quadrangle
No full textIn this paper, the association scheme defined on the flags of a finite generalized quadrangle is considered. All possible fusions of this scheme are listed, and a full description for those of classes 2 and 3 is given.
Furthermore, it is showed that an association scheme with appropriate parameters must arise from the flags of a generalized quadrangle. The same is done for one of its 4-class symmetric fusion
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