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Calcolo del moltiplicatore di collasso di ponti in muratura fondato su due nuovi teoremi di analisi rigido-plastica

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Article
A stepwise iterative procedure for the nonlinear analysis of multispan arch bridges, suitable for implementation by standard programming of commercial finite element codes, is discussed. Relying on the plane section hypothesis, masonry is assumed elastic-perfectly plastic in compression and no tensile resistant; a collapse condition is found when an ultimate strain is reached. The iterative procedure is that of an elastic prevision and subsequent nonlinear correction of the nodal forces: tensile stresses are not allowed in the mortar joint by adapting the effective height of the arch to its compressed part, while the plastic response is represented by additional external fictitious forces accounting for the compressive plastic plateau. The procedure is first tested by comparison with experimental data and then applied to sample bridges, pointing out how the collapse mechanism and the ultimate load depend on the geometric and mechanical parameters.
Article
Sommario L'argomento è la ricerca del moltiplicatore di collasso di un arco in muratura operando in regime elastico. L'approccio permette la conoscenza delle sollecitazioni e delle lesioni sotto i carichi accidentali di esercizio, cosi come in prossimità del collasso. E' messo in rilievo l'effetto di variazioni termiche e carichi sismici.
Article
The paper describes the application of limit principles, derived from the plastic analysis of steel structures, to the masonry arch. Most voussoir arches have low stresses, and the lines of thrust lie well within the masonry, so that conventional factors of safety on stress have little relevance. However, a “geometrical” factor of safety may be defined by consideration of the arch of minimum thickness, of the same shape as the real arch, which would just contain a proper line of thrust. If the real profile of the arch is then discarded, and the calculations referred to an arch having the profile of the ideal line of thrust, it is shown that a simple analysis may be made of the effect of travelling point loads. The ideas are applied to the analysis of two actual bridges: (a) the stone arch between the western towers of Lincoln Cathedral, and (b) the Ponte Mosca in Turin. The paper is concerned only with the action of the masonry, and not with the design of the abutments to resist the thrust of the arch. However, the effect of geometry changes due to yielding of the abutments is discussed.
analisi plastica allo studio degli archi è iniziata con l'ipotesi semplificativa di resistenza infinita, e con l'utilizzo del metodo cinematico
  • Storicamente
Storicamente, l'applicazione dell'analisi plastica allo studio degli archi è iniziata con l'ipotesi semplificativa di resistenza infinita, e con l'utilizzo del metodo cinematico.
The first application of the modern theorems of limit design to the problem of masonry construction seems to have been by Kooharian
  • Heyman Lo Stesso
Lo stesso Heyman, nell'importante articolo del 1969 [5] scrive: "The first application of the modern theorems of limit design to the problem of masonry construction seems to have been by Kooharian..." La prima applicazione agli archi del calcolo plastico (1953).
Mechanical Principles of Engineering and Architecture
  • H Moseley
Moseley H., Mechanical Principles of Engineering and Architecture, New York, 1856.
Il Teorema della Minima Compressione Equilibrata per il calcolo del moltiplicatore di collasso di archi murari non reagenti a trazione (The minimum equilibrated compression theorem for the calculation of the multiplier of collapse of no tension arches)
  • G Stagnitto
Stagnitto G., Il Teorema della Minima Compressione Equilibrata per il calcolo del moltiplicatore di collasso di archi murari non reagenti a trazione (The minimum equilibrated compression theorem for the calculation of the multiplier of collapse of no tension arches), Università degli Studi di Pavia, 2016.
Strength assessment of ancient masonry vaults: integration of classical and modern methods of structural analysis
  • A Cauvin
  • G Stagnitto
Cauvin A, Stagnitto G., Strength assessment of ancient masonry vaults: integration of classical and modern methods of structural analysis, Proc. IABSE Symposium Structural preservation of the Architectural Heritage, Roma, 379-384,1993.
Test on stone masonry arch at Bridgemill -Girvan
  • A Hendry
  • W Davies
  • S R Royles
Hendry A., W., Davies S.R., Royles R., Test on stone masonry arch at Bridgemill -Girvan, TRRL Contractor Report 7, Crowthorne, 1985.