Dynamic One-Sided Out-Of-Plane Behavior of Unreinforced-Masonry Wall Restrained by Elasto-Plastic Tie-Rods

Past earthquakes have shown the high vulnerability of existing masonry buildings, particularly to out-of-plane local collapse mechanisms. Such mechanisms can be prevented if façades are restrained by tie rods improving the connections to perpendiculars walls. Whereas in the past only static models have been proposed, herein the nonlinear equation of motion of a monolithic wall restrained by a tie rod is presented. The façade, resting on a foundation and adjacent to transverse walls, rotates only around one base pivot and has one degree of freedom. Its thickness is explicitly accounted for and the tie rod is modeled as a linear elastic—perfectly plastic spring, with limited displacement capacity. The model is used to investigate the response to variations of wall geometry (height/thickness ratio, thickness), tie rod features (vertical position, length, prestress level), and material characteristics (elastic modulus, ultimate elongation, yield strength) typical of historical iron. The most relevant parameter is the steel strength, whereas other characteristics play minor roles allowing to recommend reduced values for pre-tensioning forces. The force-based procedure customary in Italy for tie design is reasonably safe and involves protection also against collapse, although probably not enough as desirable.     

Force-Based Beam Finite Element (FE) for the Pushover Analysis of Masonry Buildings

A simplified approach for analyzing the nonlinear response of masonry buildings, based on the equivalent frame modeling procedure and on the nonlinear equivalent static analyses, is presented. A nonlinear beam finite element (FE) is formulated in the framework of a force-based approach, where the stress fields are expanded along the beam local axis, and introduced in a global displacement-based FE code. In order to model the nonlinear constitutive response of the masonry material, the lumped hinge approach is adopted and both flexural and shear plastic hinges are located at the two end nodes of the beam. A classical elastic-plastic constitutive relationship describes the nonlinear response of the hinges, the evolution of the plastic variables being governed by the Kuhn-Tucker and consistency conditions. An efficient element state determination procedure is implemented, which condenses the local deformation residual into the global residual vector, thus avoiding the need to perform the inner loops for computing the element nonlinear response. The comparison with some relevant experimental and real full-scale masonry walls is presented, obtaining a very good agreement with the available results, both in terms of global pushover curves and damage distributions.     

The political functions of virtue in the eighteenth-century Italian debate

Many recent studies either assert that the concept of virtue in eighteenth-century Italian intellectual culture is a polysemous term without really explaining its meaning, or concentrate on just one of its many facets. However, so far no study has explored the shades of meaning ascribed to ‘virtue’ to their full extent. This study is an attempt to reconstruct the eighteenth-century Italian intellectual perspective on virtue and to reveal its geographical complexities, its semantic evolutionary curve, and its interconnections in different fields. The aim is not to create a simple ‘map’, but rather to focus on the limits of the intellectual debate in defining and communicating virtue, and to envisage the understanding of the political functions of virtue through more popular and widespread media such as poetic texts. Despite its ever-changing meaning, virtue remains not only a keyword of political discourse over the century, but also stands as one of the very pillars on which powerful imageries of political communication were constructed. Therefore, this article provides a first step towards an analysis of political communication in eighteenth-century Italy, which, in subsequent studies, will take into account poetic sources, which at that time were regarded as an effective instrument to overcome the aforementioned intellectual limits and better exploit the possibilities of a rhetoric of virtue.     

Towards an Archaeology of Disentanglement

The impact of connectivity in past societies has long been a focus of archaeological studies. Well-established approaches have been developed over the years to understand emergent connections and entanglement between distant communities, including world system, culture contact, post-colonial theories and network analyses. Our understanding of connectivity remains partial, however, because researchers have focussed on the establishment and consequences of contact and largely ignored the dynamics that often led to its interruption. Yet these processes of ‘disentanglement’ are just as complex and far-reaching as their converse and need to be understood in their own right. This paper shows that a thorough analysis of disentanglement processes can contribute to our understanding of the very nature of the interrupted contacts, as well as shed light on the social dynamics that engender long-term changes in contact patterns. The concept of disentanglement is discussed in the light of current theories of connectivity and explored through regional case studies in Late Bronze Age Italy (Salento) and Greece (Achaea).     

Simulation Of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (II): Combined Finite-Discrete Elements

ABSTRACT

Out-of-plane response of unreinforced masonry elements is frequently the most critical aspect of the seismic performance of existing masonry buildings. The response of such elements is usually governed by equilibrium rather than strength. Hence, it is customary to resort to rigid-body models, accounting for possible rotations, and/or sliding. However, the results of such analyses depend on the initial choice of the mechanism. In this article, the shaking-table experiments on a brick-masonry specimen, and on a stone-masonry specimen have been modeled by resorting to a combined finite-discrete element strategy. Despite the coarse discretization of both discrete and finite elements, the three-dimensional models are able to capture the experimentally observed multi-degree-of-freedom mechanisms, without any a priori assumption on the mechanism. A sensitivity analysis is carried out, addressing eight different parameters. The identification of the mechanism is sufficiently robust, but the assessment of its activation and failure is best done by combining the finite-discrete element model with a simplified model of the recognised mechanism.     

Testing flora as bioindicator of buried structures in the archaeological area of Maxentius’s villa (Rome,Italy)

The flora of the archaeological area of Maxentius’s villa (Rome) was tested as bioindicator of buried remains of masonry and pavements. A total of 53 floristic surveys provided the occurrence of each species in sample units, as well as some their phenological features. The data were elaborated through multivariate statistical analysis in order to assess floristic affinities/differences among sample units, and define their ecological characteristics. The fuzzy set methodology was applied to evaluate relation between floristic richness, plant cover and soil depth. Results showed that the buried remains of stonework create a discontinuity in the ground, influencing the flora growing above it. This phenomenon may give rise to differential presence of some species (e.g., Cota tinctoria, Trifolium scabrum ssp. scabrum on thin soil; Ranunculus bulbosus, Trifolium pratense on deeper soil), but will not have such a great effect on floristic richness. The bioindication of this phenomenon also occurs through phenological irregularities in single specimens and changes in plant cover. Nevertheless other environmental factors (soil moisture/aridity, trampling, enrichment of nitrogen, cutting, ground depression) can interfere with the use of plants as bioindicators of buried structures. It is therefore necessary to consider other factors ecological influencing each site when you want to use plants as bioindicators in archaeological prospection.     

Seismic Risk Assessment of New Zealand Unreinforced Masonry Churches using Statistical Procedures

ABSTRACT

The 2010–2011 Canterbury earthquake sequence provided extensive evidence of the significant seismic vulnerability of New Zealand unreinforced masonry (URM) churches. Given the high seismicity of the country, the exposure of human lives and the societal significance of ecclesiastic buildings, for both historical and religious reasons, the reduction in seismic vulnerability of this building type is of primary importance. By analyzing the seismic performance of a sample of 80 affected buildings, regression models correlating mean damage levels against ground-motion parameters were developed for observed collapse mechanisms, accounting for vulnerability modifiers whose influence was estimated via statistical procedures. Considering the homogeneity of New Zealand URM churches, the vulnerability models developed for the Canterbury region were extended to the whole country inventory, and a synthetic index was proposed to summarise damage related to several mechanisms. Territorial scale assessment of the seismic vulnerability of churches can assist emergency management efforts and facilitate the identification of priorities for more in-depth analysis of individual buildings. After proper calibration, the proposed approach can be applied to other countries with similar building heritage.