In consideration of the high vulnerability of the built environment, the assessment of seismic behavior of existing masonry buildings is a key topic in view of their retrofitting and reuse. Because masonry's behavior depends on complex nonhomogeneous, anisotropic, asymmetric, and nonlinear properties, the definition of suitable mechanical models is still a critical issue, especially for stone masonry. Structural analyses of existing masonry buildings in seismic-prone areas are thus significantly influenced by the adopted mechanical models and assumptions about their relevant masonry properties, which are characterized by large uncertainty. In this study, a procedure for the definition of masonry classes and probability density functions of relevant mechanical parameters, such as elastic modulus and shear modulus, is proposed. The general procedure is illustrated referring to a significant number of in situ double-flat-jack test results on stone masonry obtained by the authors during an ad hoc experimental campaign. Finally, combining information on masonry quality obtained by visual inspection with results of in situ tests, a Bayesian methodology is proposed for the updating of masonry mechanical parameters, thereby providing the basis for a more refined probabilistic assessment of the seismic risk index.

In the architecture, engineering and construction sectors, Building Information Modeling (BIM)-based procedures have become adopted more and more. In fact, the development of suitable BIM models facilitates the management of the design and construction phases and improves the efficiency of the maintenance policies during the life cycle of the building. Although the BIM method is mostly implemented in the building industry for new constructions, in recent years, the deployment of this technology has also attracted increasing attention for existing structures to rebuild their geometry and gather relevant data, especially for historical buildings; in this case, we refer to Heritage BIM (HBIM). A HBIM procedure requires a multidisciplinary approach involving not only historical, conservation, and restoration considerations but also suitable maintenance and repair plans, duly balancing the structural needs with the preservation of the historical value of the building and its content. Although the integration of the structural assessment in the HBIM process would be highly beneficial, its practical implementation is often in the early stages. In the paper, an original parametric procedure for the assessment of existing masonry buildings is proposed in the BIM environment. The procedure combines E-PUSH, a software program for the structural analysis of masonry structures under seismic and non-seismic actions with an appropriate BIM approach, so improving the management of gathered data through cognitive phases. The assessment process is, thus, simplified since data required for the structural analysis are directly retrieved from the BIM model, and the structural analyses and verifications are performed without using external programs. The proposed BIM workflow is finally illustrated and discussed referring to a relevant case study, the seismic vulnerability assessment of the “Bernardo Rucellai” school in Florence (Italy).

The evaluation of the shear behavior of masonry walls is a first fundamental step for the assessment of existing masonry structures in seismic zones. However, due to the complexity of modelling experimental behavior and the wide variety of masonry types characterizing historical structures, the definition of masonry’s mechanical behavior is still a critical issue. Since the possibility to perform in situ tests is very limited and often conflicting with the needs of preservation, the characterization of shear masonry behavior is generally based on reference values of mechanical properties provided in modern structural codes for recurrent masonry categories. In the paper, a combined test procedure for the experimental characterization of masonry mechanical parameters and the assessment of the shear behavior of masonry walls is presented together with the experimental results obtained on three stone masonry walls. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is executed to derive the normal compressive stress acting on the wall. Then a double flat jack test is carried out to estimate the elastic modulus. Finally, the proposed shear test is performed to derive the capacity curve and to estimate the shear modulus and the shear strength. The first results obtained in the experimental campaign carried out by the authors confirm the capability of the proposed methodology to assess the masonry mechanical parameters, reducing the uncertainty affecting the definition of capacity curves of walls and consequently the evaluation of seismic vulnerability of the investigated buildings.

The evaluation of seismic performance of existing masonry structures is a fundamental issue for the preservation of cultural heritage in general and of historical buildings in particular, even in view of the adoption of suitable policies for risk mitigation. To assess the seismic performance of existing masonry buildings, several refined push-over procedures for non-linear static analysis can be found in literature, mainly based on the equivalent frame approach. However, these procedures are not only very time consuming, but also very sensitive to modelling hypotheses, so that results could vary in a large interval even when users are very skilled. To solve these problems, the authors, aiming to enhance the classical pushover programs for masonry building, especially in terms of easiness of use, simplicity of modelling and computational demand, developed a reliable and sound push-over procedure allowing a quick evaluation of seismic risk index. The so called E-PUSH program, which allows the verification of multi-story masonry buildings according to the most recent structural codes and relies on very simple structural models, has been validated considering several relevant benchmark studies and comparing the results with classical procedures implemented in commercial programs. In the paper, a review of macro-element methods for the seismic assessment of unreinforced masonry buildings is then discussed considering the main hypothesis on masonry modelling, choice of masonry mechanical parameters and failure criteria and evaluating their impact on the estimation of seismic risk index. The results of the comparison will be finally presented and discussed for a relevant case study of a four story masonry building investigated by the authors in the framework of a research program agreement between the Municipality of Florence and the Department of Civil and Industrial Engineering of the University of Pisa.

<p>Masonry structures represent a large part of existing buildings. As confirmed by the damage caused by recent seismic events, the assessment of seismic performance of existing masonry building is then a critical issue in Countries exposed to seismic risk. Moreover, common methods of analysis based on non-linear static approach are significantly influenced by the assumptions about the shear behavior of masonry walls and may lead to inconsistent or contradictory results.</p><p>Due to the relevance of the problem ad hoc studies have been performed to clarify how the most relevant parameters affect the theoretical structural behavior and to setup a proper method to define these parameters.</p><p>In the paper, the main sources of uncertainties regarding the definition of material parameters are investigated and a methodology for the identification of masonry classes is illustrated discussing the propagation of uncertainties related to masonry parameters in non-linear static analysis of masonry buildings. The analysis are carried out through a simplified non-linear pushover type algorithm developed by the authors and the outcomes are illustrated and critically discussed for a relevant case study.</p><p>The results show the capability of the proposed procedure for the identification of masonry classes and the evaluation of masonry mechanical parameters to provide a more refined probabilistic assessment of the seismic risk index.</p>

<p>BIM-based processes are becoming increasingly relevant in architecture, engineering and construction industries, especially for design of new engineering works. Implementation of this technology for existing buildings, Heritage BIM (HBIM), mainly focuses on the reconstruction of geometries and the collection of historical documentation, while areas of structural analyses and verifications are currently less developed.</p><p>In this context, a parametric procedure in BIM environment for the structural assessment of existing masonry buildings is proposed, starting from an innovative analysis method previously developed by the authors (E-PUSH). Combining this structural analysis program with the advantages of the BIM methodology, the management of the data is improved and the assessment process is simplified.</p><p>The proposed BIM workflow will be illustrated in detail with reference to a real case study, showing benefits of the BIM approach in the process of seismic risk assessment.</p>

Historical and cognitive investigations supported by in-situ and/or laboratory tests are needed for a robust reliability assessment of existing structures. Indeed, an adequate knowledge of material properties and their statistical description is the basis for carrying out accurate reliability analyses and verifications on the investigated structures. In this paper, a procedure for the definition of pdfs of mechanical parameters of steel rebars is proposed based on secondary experimental test data. This information is very helpful for the reliability assessment of existing r.c. buildings, where estimation of statistical parameters of mechanical properties of steel reinforcement is very difficult. In fact. It must be highlighted on the one hand that direct information about the examined structure are commonly not sufficient, on the other hand that the number of rebar samples extracted from the structure, if available, is so limited that it does not allow a complete statistical analysis. The first step has been the collection of experimental acceptance tests carried out by Department of Civil and Industrial Engineering of University of Pisa on steel rebars of reinforced concrete (r.c.) structures during the 1960s. The yield strength and the tensile strength are extrapolated for each sample defining a significant database of experimental test results for existing r.c. structures. Then, probability distribution models for the mechanical properties of steel reinforcement have been defined as already done by the authors for concrete strength. A cluster analysis has been carried out based on the Gaussian Mixture Model applying the Expectation-Maximization algorithm to identify homogeneous material classes and their associated pdfs of material mechanical parameters. The main advantage of proposed procedure consists in its "blindness", In fact, not requiring subjective information like pre-classification of data, the methodology is not sensitive to alterations caused by engineering judgement or by inexact identification of declared strength class of the tested samples, due for example to downgraded materials.

The evaluation of seismic vulnerability of existing masonry building is a first fundamental step for the preservation of historical buildings in seismic prone area.However, the definition of masonry's mechanical behavior, which is characterized by a complex, nonhomogeneous, anisotropic, non-linear behavior, is still a critical issue that significantly influences the structural analysis and the evaluation of seismic risk index. Different test procedures have been proposed in the past such as double flat jack, diagonal compression and shear compression tests to characterize the masonry behavior; but their outcomes are often contradictory and can differ significantly for the same class of masonry or even for the same wall.In the paper, a new test procedure for the characterization of masonry mechanical parameters and especially the shear behavior of masonry walls is presented together with the experimental test results obtained for a stone masonry wall and a brick masonry wall. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is done to derive the normal compressive stress acting on the wall, then a double flat jack test is carried out to estimate the elastic modulus and finally a shear test is performed to directly assess the capacity curve and estimate the shear modulus and the shear strength.The first results obtained in the experimental campaign carried out by the authors show the capability of the proposed methodology that allows a complete assessment of masonry mechanical parameters reducing the uncertainty in the estimation of shear behavior and consequently on the evaluation of seismic vulnerability of the investigated buildings.