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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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Seventh wrangler in the Cambridge mathematical tripos in 1826, Henry Moseley (1801–72) was adept at applying mathematical analysis to a wide variety of problems. Appointed professor of natural and experimental philosophy and astronomy at London's newly established King's College in 1831, he was instrumental in creating the institution's department of engineering and applied science. This 1843 textbook is based on the lectures in statics, dynamics and structures that he gave to students of engineering and architecture. Moseley draws on the latest continental work in mechanics, and the treatment of problems is mathematically sophisticated. Starting with basic statics and dynamics, Moseley covers topics of interest to both civil and military engineers, with sections on the theory of machines and on the stability of walls, arches and other structures. Notably, the American edition of this work was adopted as a textbook by the United States Military Academy at West Point.
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.
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.
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).
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.