Origini dell'ucronia. La letteratura contro la storia

L’ucronia (Alternate History) è un fenomeno letterario ormai popolare e molto studiato, ma non lo sono altrettanto lo sue origini e i suoi rapporti con la storia “fatta con i se” (Counterfactual History), che risale a Erodoto e a Tito Livio. Solo nell’Ottocento alcuni autori, per vie largamente autonome, fecero della storia alternativa un genere di fiction: Louis Geoffroy con Napoléon apocryphe (1836), storia «della conquista del mondo e della monarchia universale», e Charles Renouvier con Uchronie. L’utopie dans l’histoire (1876), storia «della civiltà europea quale avrebbe potuto essere» se il cristianesimo fosse stato fermato nel II secolo. Questi testi intrattengono relazioni complesse con la letteratura dell’epoca di genere sia realistico, sia fantastico, ma altresì con fenomeni di altra natura: la storiografia, nelle sue forme e nel suo statuto epistemico, e ancor più il senso del possibile - o la filosofia della storia - derivato dall’esperienza della rivoluzione e dal confronto con le teorie utopistiche e di riforma sociale. Altri testi, prodotti in Inghilterra e negli Stati Uniti nello stesso periodo, esplorano le possibilità narrative e speculative del genere: tra questi P.s’ Correspondence di Nathaniel Hawthorne (1845), The Battle of Dorking di George Chesney (1871) e Hands Off di Edward Hale (1881); fino a una raccolta del 1931, If It Had Happened Otherwise, che anticipò molte forme e temi delle ucronie successive. Queste opere sono esaminate sia nel contesto storico e letterario in cui furono prodotte, sia con gli strumenti dell’analisi testuale. Una particolare attenzione è dedicata alle strategie di lettura prescritte dai testi, che subordinano i significati al confronto mentale tra gli eventi narrati e la serie dei fatti autentici. Le teorie sui counterfactuals prodotte in altri campi disciplinari, come la storia e la psicologia, arricchiscono la comprensione dei testi e dei loro rapporti con fenomeni extra-letterari.

Numerical modelling of rock masses interacting with dams: the case of Ridracoli

A three-dimensional Direct Finite Element procedure is here presented which takes into account most of the factors affecting the interaction problem of the dam-water-foundation system, whilst keeping the computational cost at a reasonable level by introducing some simplified hypotheses. A truncated domain is defined, and the dynamic behaviour of the system is treated as a wave-scattering problem where the presence of the dam perturbs an original free-field system. The rock foundation truncated boundaries are enclosed by a set of free-field one-dimensional and two-dimensional systems which transmit the effective forces to the main model and apply adsorbing viscous boundaries to ensure radiation damping. The water domain is treated as an added mass moving with the dam. A strategy is proposed to keep the viscous dampers at the boundaries unloaded during the initial phases of analysis, when the static loads are initialised, and thus avoid spurious displacements. A focus is given to the nonlinear behaviour of the rock foundation, with concentrated plasticity along the natural discontinuities of the rock mass, immersed in an otherwise linear elastic medium with Rayleigh damping. The entire procedure is implemented in the commercial software Abaqus®, whose base code is enriched with specific user subroutines when needed. All the extra coding is attached to the Thesis and tested against analytical results and simple examples. Possible rock wedge instabilities induced by intense ground motion, which are not easily investigated within a comprehensive model of the dam-water-foundation system, are treated separately with a simplified decoupled dynamic approach derived from the classical Newmark method, integrated with FE calculation of dam thrust on the wedges during the earthquake. Both the described approaches are applied to the case study of the Ridracoli arch-gravity dam (Italy) in order to investigate its seismic response to the Maximum Credible Earthquake (MCE) in a full reservoir condition.

Application of Submerged Grouted Anchors in Sheet Pile Quay Walls

Sheet pile walls are one of the oldest earth retention systems utilized in civil engineering projects. They are used for various purposes; such as excavation support system, cofferdams, cut-off walls under dams, slope stabilization, waterfront structures, and flood walls. Sheet pile walls are one of the most common types of quay walls used in port construction. The worldwide increases in utilization of large ships for transportation have created an urgent need of deepening the seabed within port areas and consequently the rehabilitation of its wharfs. Several methods can be used to increase the load-carrying capacity of sheet-piling walls. The use of additional anchored tie rods grouted into the backfill soil and arranged along the exposed wall height is one of the most practical and appropriate solutions adopted for stabilization and rehabilitation of the existing quay wall. The Ravenna Port Authority initiated a project to deepen the harbor bottom at selected wharves. An extensive parametric study through the finite element program, PLAXIS 2D, version 2012 was carried out to investigate the enhancement of using submerged grouted anchors technique on the load response of sheet-piling quay wall. The influence of grout-ties area, length of grouted body, anchor inclination and anchor location were considered and evaluated due to the effect of different system parameters. Also a comparative study was conducted by Plaxis 2D and 3D program to investigate the behavior of these sheet pile quay walls in terms of horizontal displacements induced along the sheet pile wall and ground surface settlements as well as the anchor force and calculated factor of safety. Finally, a comprehensive study was carried out by using different constitutive models to simulate the mechanical behavior of the soil to investigate the effect of these two models (Mohr-Coulomb and Hardening Soil) on the behavior of these sheet pile quay walls.