Andrea Chiozzi

ArchNURBS: NURBS-Based Tool for the Structural Safety Assessment of Masonry Arches in MATLAB

AbstractA new approach toward a fully computer-aided design (CAD) integrated structural analysis of arched masonry structures is proposed and a new MATLAB-based computational tool, named ArchNURBS, is developed. It is addressed to professionals dealing with the restoration or structural rehabilitation of historical constructions, who need to assess the safety of masonry arches under assigned load distributions. By using it, they can easily produce estimates of the carrying capacity of curved masonry members, and specifically arches of arbitrary shape. A CAD environment, which is very popular among professionals, can be employed to provide a nonuniform rational B-splines (NURBS) representation of arch geometry. On the basis of this representation, it is possible to perform both an elastic isogeometric analysis and a limit analysis of the structure up to the collapse load. Moreover, the developed tool is devised for handling the presence of fiber-reinforced polymers reinforcement strips at the extrados and/...

Numerical insights on the seismic behavior of a non-isolated historical masonry tower

In this paper, numerical insights on the seismic behavior of a non-isolated historical masonry tower are presented and discussed. The tower under study is the main tower of the fortress of San Felice sul Panaro, a town located near the city of Modena (Italy). Such a tower is surrounded by adjacent structural elements and, therefore, is not isolated. This historical monument has been hit by the devastating seismic sequence occurred in May 2012 in the Northern part of the Emilia region (the so-called “Emilia earthquake”), showing a huge and widespread damage. Here, in order to understand the behavior of the structure, its interaction with the adjacent buildings and the reasons of the occurred damage, advanced numerical analyses (both nonlinear static and dynamic) are performed on a 3D finite element model with different levels of constraint supplied by the adjacent structural elements and a detailed comparison between the simulated damage and the actual one is carried out. The results of the conducted numerical campaign show a good agreement with the actual crack pattern, particularly for the model of the tower that considers the adjacent structural elements.

Fast Kinematic Limit Analysis of FRP-Reinforced Masonry Vaults. I: General Genetic Algorithm–NURBS–Based Formulation

AbstractA new approach for the limit analysis of masonry vaults retrofitted with fiber-reinforced polymers (FRP) based on an upper bound formulation is presented in this paper. In particular, a new...

Fast Kinematic Limit Analysis of FRP-Reinforced Masonry Vaults. II: Numerical Simulations

AbstractA new approach for limit analysis of masonry vaults retrofitted with fiber-reinforced polymers (FRPs) based on an upper bound formulation is presented. Part I of this paper was devoted to d...

SEISMIC PROTECTION OF HEAVY NON-STRUCTURAL MONOLITHIC OBJECTS AT THE TOP OF A HISTORICAL MASONRY CONSTRUCTION THROUGH BASE ISOLATION

This contribution addresses the problem of earthquake protection of heavy nonstructural monolithic objects, which are usually placed at the top of historical masonry constructions for mainly decorative purposes like pinnacles, merlons, sculptures and heavy artwork. Such objects, when subjected to base accelerations due to seismic actions, may undergo rocking phenomena, which may eventually lead to the overturning of the whole body. In particular, the specific case of the seismic protection of ancient marble pinnacles placed at the top of a three-arched masonry city gate in Ferrara (ITALY) is illustrated. In a preliminary rocking analysis, the pinnacles have been idealized as rigid bodies in unilateral contact with the underlying moving base and the resulting rocking motion have been analyzed. The structural safety level of the pinnacles have thus been assessed. As a consequence of these considerations, a base isolation system designed around multiple double concave curved-surface steel sliders have been devised. The effectiveness of the proposed isolation system has been assessed through numerical simulations. The amplification effect of the ground acceleration due to the underlying three-arched structure has been established through time-history dynamic analyses, where masonry has been considered as a viscoelastic material. To this aim, an equivalent viscous damping coefficient has been calculated for masonry following an iterative procedure involving the computation of capacity curves for both inand out-of-plane load directions and the definition of simplified biand tri-linear inelastic load-displacement capacity curves for masonry panels.

On the analysis of the stellar vault of Santa Maria del Monte in Cagliari

The aim of this paper is to study the statics of the stellar (i.e. star-shaped) vault of the church of Santa Maria del Monte in Cagliari. This church, which was built during the second half of the 16th century, is a beautiful example of Gothic-Catalan style and the ribbed stellar vault is one of the most representative of this type in the town of Cagliari. A comparison between a static finite element non-linear analysis carried out with the commercial code Diana and a limit analysis performed with a method recently developed by the research team of the University of Ferrara is presented.

Fast and Reliable Limit Analysis Approach for the Structural Assessment of FRP-Reinforced Masonry Arches

This contribution is devoted to assess the capability of a new upper-bound approach for the limit analysis of FRP-reinforced masonry arches by comparing it to both experimental tests and a number of existing numerical procedures. The approach is based on an idea previously presented by the Authors and relies on the representation of the geometry of both the arch and of FRP reinforcement through Non Uniform Rational B-Spline (NURBS) functions. This allows generating a rigid body assembly starting from the assigned geometry composed by very few elements which still provide an exact representation of the original shape. A homogenized kinematic formulation for the limit analysis of the obtained rigid blocks assembly is derived, which accounts for the main properties of masonry material. FRP material is included exploiting the Italian CNR Recommendations for the design of FRP based reinforcing interventions. The approach is capable of accurately predicting the load bearing capacity of masonry arches of arbitrary geometry, provided that the initial mesh is adjusted by means of a suitably devised Genetic Algorithm (GA) until the active interfaces among blocks (e.g. hinges) closely approximate the actual failure mechanism.

FAST KINEMATIC LIMIT ANALYSIS OF MASONRY WALLS WITH OUT-OF-PLANE LOADING

Masonry structures represent one of the commonest structural typologies for buildings worldwide. In particular, masonry walls constitute, by far, the prevailing elementary structural unit in the majority of masonry constructions both modern and historical. This contribution validates an approach proposed by the authors for the limit analysis masonry vaults, now extended to a new general procedure for the structural assessment of masonry walls with out-of-plane loading based on an upper bound formulation. A given masonry panel of arbitrary form possibly with openings is described through its NURBS (Non-Uniform Rational B-Spline) parametric representation in the three-dimensional Euclidean space. An initial set of rigid elements subdividing the original wall geometry is identified through the definition of a suitable lattice of nodes. An upper-bound limit analysis formulation, taking into account the main characteristics of masonry material through homogenization, is deduced where internal dissipation is allowed along element edges only. As shown in a number of examples, a good estimate of the collapse load is obtained, provided that the initial net of yield lines is suitably adjusted by means of a Genetic Algorithm (GA). 2404 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 2404-2412

DRIFT-BASED FRAGILITY ASSESSMENT OF MASONRY INFILLS

Masonry infills represent one of the prevailing types of non-structural elements in buildings of both Western and Eastern modern architecture. Recent seismic events have provided evidence that damage on masonry infills can lead not only to large economic losses but also to significant injuries and even fatalities. The estimation of damage of such elements and the corresponding consequences within the Performance-Based Earthquake Engineering (PBEE) framework, requires reliable fragility curves. Although there is an important body of work on testing masonry infills, there is very limited work that has led to the definition of fragility functions. This contribution presents drift-based fragility functions developed for inplane loaded masonry infills, derived from a comprehensive experimental dataset gathered from current literature, comprising 152 specimens of infilled RC or steel frames tested under lateral cyclic loading, with different types of masonry blocks. Three key damage states associated with the structural performance and reparability of infill walls have been defined. In particular, four sources of uncertainty are evaluated: specimen-to-specimen, finite-sample, measured mortar compression strength and prism compression strength, presence of openings. The fragility curves developed in the present study are very useful for estimating damage and expected earthquake-induced economic losses for infilled buildings, by employing recently proposed methodologies based on aggregating the estimated damage at the component level for a specific structure. 1816 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 1816-1827