Chiara Calderini

PERPETUATE Project: The Proposal of a Performance-Based Approach to Earthquake Protection of Cultural Heritage

The paper describes the methodology proposed in the PERPETUATE Project (funded by the Seventh Framework Programme – Theme ENV.2009.3.2.1.1). The methodology proposed in PERPETUATE uses a displacement-based approach for the vulnerability evaluation and design of interventions. The use of safety verification in terms of displacement, rather than strength, orients to new strengthening techniques and helps in the comprehension of interaction between structural elements and unmovable artistic assets. The procedure is based on the following fundamental steps: definition of performance limit states, specific for the cultural heritage assets (considering both structural and artistic assets); evaluation of seismic hazard and soil-foundation interactions; construction knowledge (non-destructive testing, material parameters, structural identification); development of structural models for the seismic analysis of masonry structures and artistic assets and design of interventions; application and validation of the methodology to case studies. Two main scales are considered: the seismic risk assessment at territorial scale and at the scale of single historic building or artistic assets. The final aim of the project is to develop European Guidelines for evaluation and mitigation of seismic risk to cultural heritage assets.

A MICROMECHANICAL INELASTIC MODEL FOR HISTORICAL MASONRY

A micromechanical damage model for the Snite element modelling of historical masonry structures is presented in this article. Masonry is considered as a composite medium made up of a periodic assembly of blocks connected by orthogonal bed and head mortar joints. The constitutive equations, in plane stress, are based on the homogenisation theory and they consider the non linear stress-strain relationship in terms of mean stress and mean strain. Different in-plane damage mechanisms, involving both mortar and blocks, are considered and the damage process is governed by evolution laws based on an energetic approach derived from Fracture Mechanics and on a non-associated Coulomb friction law. The failure domain of the model is analysed both in the equivalent stress and in the principal stress space considering different orientations of the bed joints relative to the loading direction. A comparison with experimental results is provided. A numerical simulation of masonry walls subjected to horizontal forces proportional to their own weight is shown in order to discuss the models capability of describing the influence of the masonry microstructure on its mechanical behaviour.

Modeling Strategies for the World's Largest Elliptical Dome at Vicoforte

With its internal axes of 37.23 by 24.89 m, the dome of the Sanctuary of Vicoforte, Italy, is the fifth biggest in the world in absolute terms, and by far the largest elliptical dome ever built. The dome-drum system has suffered since the beginning from significant structural problems, partly due to soil settlements, and, to a considerable extent, arising from its bold structural configuration. This article deals with the modeling strategies adopted in the assessment of the structural reliability of the monument, a project undertaken in recent years following the strengthening intervention operated in 1985 with the application of active tie-bars around the perimeter at the top of the drum. The structural behavior of the construction was modeled according to two different approaches: limit analysis and finite element analysis based on linear and non-linear constitutive models for the masonry.

Experimental testing of the seismic in-plane displacement capacity of masonry cross vaults through a scale model

Since cross masonry vaults represent one of the more widespread types of horizontal structural elements in historical constructions, understanding their behaviour is a crucial precondition for the accurate assessment of the global response of buildings to earthquakes. In spite of the importance of this topic, the complexity of evaluation three-dimensional response of vaults still represents a challenge for researchers. Experimental investigations can be a valid tool to analyse this difficult problem, as they provide useful results that can validate the reliability of the numerical and analytical tools developed for analysis. In this paper, the results of an experimental campaign on 1:5 scale model of a masonry cross vault are presented. The main aim was to evaluate the response of the vaults in the context of a global analysis of historic masonry buildings by determining their ultimate in-plane seismic capacity (diaphragm effect) in terms of stiffness, strength, and ultimate displacements. Their three-dimensional damage mechanisms on the vaults was also described. The model, made of 3D printed plastic blocks with dry joints, was tested by statically applying different horizontal displacements settings to the abutments in order to simulate differential displacements of the supports (walls or pillars). In particular, in-plane horizontal shear distortions and longitudinal opening/closing of the abutments, as they are the most common seismic damage mechanisms seen in masonry vault buildings, were applied.

Seismic Response of Masonry Arches Reinforced by Tie-Rods: Static Tests on a Scale Model

This article presents an experimental study on the seismic behavior of arch-pier systems reinforced with tie-rods. In particular, the role of the tie-rod stiffness is stressed, with the aim of proposing innovative tie-rods characterized by lower stiffness than traditional ones. The experimental campaign was performed by adopting the inclined plane static test on a 1:10 scaled model. It is demonstrated that prestress applied to tie-rods barely influences the seismic capacity of the system. Moreover, it is shown that larger tie-rod deformability induces larger displacement capacity at collapse. Finally, a comparison between experimental results and simple analytical models based on rigid block systems shows the fundamental role of overall system deformability on the seismic response.

Shaking table tests of an arch-pillars system and design of strengthening by the use of tie-rods

In arches and vaults, tie-rods play a decisive role in counterbalancing horizontal thrusts produced by both permanent and seismic loadings. In this paper, the effectiveness of flexible tie-rods to improve the seismic response of arch-pillars system is assessed by means of shaking table tests and simple analytical models, developed in the framework of displacement-based design. The reduced scale model, made of rigid blocks with dry joints, has been tested without tie-rod and considering different configurations of strengthening. Both experimental and theoretical results have proved the importance, in particular for this kind of flexible masonry structure, of improving displacement capacity rather then strength, because in this latter case other brittle mechanisms could be activated. The paper shows the possibility of describing the dynamic seismic response of rocking masonry structures, characterized by complex mechanisms made of many blocks and hinges, by an equivalent nonlinear SDOF system.

Sustainable Structural Design: Comprehensive Literature Review

AbstractResearch on sustainable structural design (SSD) has increased significantly over the past decade. Having established the importance of structural engineering in sustainable development, researchers and practitioners have developed sustainable design strategies to address the impact of structural systems on the environment, economy, and society. Nevertheless, many studies have pointed out the inadequacy of existing assessment tools and the lack of overall understanding regarding the role of civil engineers and structural engineers in achieving sustainable goals. The purpose of this paper is to provide a comprehensive state-of-the-art overview of SSD, focusing on design strategies, parameters for SSD, and the role of SSD in Green Building rating systems and building codes. First, the authors will clearly identify research results in this field and then point out the biggest issues when choosing SSD strategies and evaluation parameters. To conclude, this paper will discuss the characteristic tasks of...

In-plane shear tests on masonry panels with plaster: correlation of structural damage and damage on artistic assets

In the paper, possibilities of correlation of structural damage and damage of attached artistic assets on multi-leaf stone masonry walls by means of destructive and non-destructive testing (NDT) methods are investigated. Results from two testing campaigns carried out at the University of Genoa and University of Ljubljana are briefly presented. In particular, diagonal tests with different levels of pre-compression and shear tests under different boundary conditions were carried out in Genoa and Ljubljana, respectively. During the tests, different damage limit states (DL) of both masonry walls (SE) and attached plasters (AA) were investigated by means of NDT’s. Two different types of rubble stone masonry were considered (uncoursed random rubble vs. coursed squared rubble). For AA the results are presented in relative form in dependence from the DL of SE. Obtained results are influenced both by the type of test and tested masonry. Results of NDT revealed strong potential and a need for data fusing of both investigated methods for the evaluation of the state of the degradation behind the plaster.

Use of Reinforced Concrete in Preservation of Historic Buildings: Conceptions and Misconceptions in the Early 20th Century

This article analyzes the cultural and technical reasons that led to the widespread use of reinforced concrete in the restoration of monuments in the first half of the twentieth century (1900–1945). The restoration theories of the epoch, affirming the concept of conservation and recognisability of the interventions, supplied theoretical legitimacy for the new material. The assertion of a new concept of safety, based on models and quantifiable parameters, and its public recognition, led the state to attribute the responsibility for the safety of monumental buildings to the new technical class of engineers. The affirmation of this technical class coincided with the abandoning of the traditional art of building, but, at the same time, with the abandoning of research into and experimentation on masonry structures. The lack of knowledge that resulted from this, together with an unlimited confidence in new building systems, were the basis for many of the interventions in reinforced concrete carried out in that epoch. This article includes an analysis of the cultural and technical reasons that led to the widespread use of reinforced concrete in restoration, a description of its technical evolution, starting from the very first applications to appear at the great consolidations of the 1930s, and, finally, a detailed analysis of two case studies (the tower of San Antonino in Piacenza and the San Gaudenzio basilica in Novara). Particular reference is made to Italy.

Three-Dimensional Limit Analysis of the Vicoforte Elliptical Dome

Limit analysis provides a conceptually simple and robust method to estimate the safety of structures and has been long applied to the analysis of the ultimate collapse state of two-dimensional masonry structures or structural elements. In revolving symmetric domes, the three-dimensional problem can be reduced to the two-dimensional case under appropriate hypotheses. The Vicoforte dome is the largest elliptical dome in the world, and its complex geometry makes this kind of analysis not straightforward. Starting from some basic assumptions, a method for analyzing the three-dimensional elliptical geometry and understand the behavior at collapse of the drum-dome system using limit analysis is proposed. The three-dimensional collapse mechanism is found and the system behavior including the presence of tension rings at different levels is interpreted. The results are compared against a nonlinear finite element model.