1,721,073 research outputs found
Notched columns made of quasi-brittle materials: stability analysis by means of R-curves
No full textThe stability of columns made of quasi-brittle materials, subjected to an eccentric
axial force, is investigated in this study, on the assumption that the base section is
notched. As a matter of fact, looking at historical structures, there is a large
number of columns made of quasi-brittle materials (stones and bricks), exhibiting
cracks or indentations in their lowest regions, that are the most exposed to
possible impacts or to various sources of damage. Moreover, since columns are
often slender, their stability may be a relevant issue, and methods for analysing
simultaneously stability and fracture are necessary.
Stability analysis of notched slender columns is studied here by means of an
approximate analytical model, which is based on the use of R-curves and
provides an intuitive understanding of the structural behaviour
On the characteristics of optimum beams with optimum length surrounded by a Winkler’s medium
No full textIn this paper an analytical approach is used to optimize a beam surrounded by a Winkler's medium and laterally loaded by a force at the top. The optimization regards both the distribution of the mass along the beam and the beam length in order to minimize the top displacement. Therefore, after having defined a transversality condition, we implement an algorithm to optimize the length of optimum beams. After having achieved the dimensionless extremals of optimum beams with optimum length, we show that the found solutions describe a central field of moment extremals defined along the beam and with the origin at the top. Having achieved the Jacobi's condition and the strengthened Legendre's condition for an extremal of optimum beam length, a sufficient condition for a weak minimum along the beam is also achieved. Besides, a given set of cross-sections whose moment of inertia divided by a dimensioned constant is obtained by raising their area to the same exponent. The optimized distribution of the dimensionless cross-sectional area as well as the dimensionless rigidity of the Winkler's medium are intrinsic properties of all optimum beams with optimum length whose cross-sections belong to the same set
Sul progetto delle sezioni in cemento armato allo stato limite ultimo vincolato alla limitazione del livello delle tensioni in esercizio
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Fully Stressed Piles and Beams in a Winkler’s Medium, End-loaded by an Orthogonal Force, and with Optimum Length
No full textA simplified method of designing fully stressed beams with optimum length in a Winkler’s medium, laterally loaded at the top and without any point constraint, is proposed. A numerical algorithm distributing the mass by means of the Fully Stressed Design (FSD) method and updating the moment with finite elements has been first implemented. The use of the FSD method is in general quite simple, and allows to obtain optimum, or close to the optimum, solutions. After having distributed the mass along the pile through the FSD method, the beam length has been finally optimised by means of a heuristic procedure
Sulla scelta della larghezza delle nervature nella produzione dei solai misti in calcestruzzo armato e laterizio
No full textOn the application of the sequential simplex method in the yield-line analysis of R/C slabs
No full textThe yield-line method is extensively used in engineering practice whenever simple R/C slabs are to be analysed at ultimate. Though the kinematic method generally leads to more or less unconservative results, it is highly appreciated because in many cases it is relatively easy to workout the “true” failure mechanism by identifying its parameters through the minimization of the collapse load. Unfortunately, when the ultimate load depends on many parameters, the method is difficult to use, even for slabs with not so many parameters; in fact since the number of non-linear equations required by the method is equal to the number of the parameters, when the parameters increase the difficulty of the solution increases rapidly as well.
In this paper the sequential simplex method is used in association with the yield- line method in the structural analysis of R/C slabs whose collapse mechanism requires many parameters. This algorithm is robust and efficient even with many parameters. Besides taking into account the constraints that often limit these parameters, the algorithm is easy to use with the exterior penalty function method leading to a successful solution of the problem.
Considering that the yield-line method seeks the direction of each line that maximizes the ultimate moment, this paper considers a further parameter concerning the two orthogonal directions of an orthotropic reinforcement. In this way the number of unknown parameters increases, but the solution shows both the least and the most favourable direction of reinforcement
Sul progetto delle sezioni in cemento armato allo stato limite ultimo vincolato in esercizio al rispetto delle verifiche di fessurazione
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Sui problemi dell’estensione della normativa tecnica sugli edifici in muratura a quelli in muratura di terra cruda
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