A crack-tracking technique for localized cohesive-frictional damage

This paper extends the use of crack-tracking techniques within the smeared crack approach for the numerical simulation of cohesive–frictional damage on quasi-brittle materials. The mechanical behaviour is described by an isotropic damage model with a Mohr–Coulomb failure surface. The correct crack propagation among the two alternative fracture planes proposed by the Mohr–Coulomb theory is selected with the use of an energy criterion based on the total elastic strain energy. The simulation of three benchmark problems of mixed-mode fracture in concrete demonstrates that the proposed methodology can reproduce the material’s frictional characteristics, showing robustness, as well as mesh-size and mesh-bias independence

A crack-tracking technique for localized damage in quasi-brittle materials

This work presents a procedure to simulate the growth and propagation of localized tensile cracks on quasi-brittle materials. The so-called smeared damage approach, which consists in standard finite elements and local nonlinear constitutive laws, is recovered and improved in order to represent crack localization and avoid spurious mesh-bias dependence in the discrete problem. This is achieved by means of the implementation of a local crack-tracking algorithm which can reproduce individual (discrete) cracks and ensure objectivity of the finite element problem solution. The performance of the localized damage model is stressed by means of the analyses of structural case-studies. Compared to the Smeared Crack Approach in its original form, the presented procedure shows clearly a better capacity to predict realistic collapse mechanisms. The proposed tracking technique is relatively inexpensive

Structural Analysis of Masonry Historical Constructions. Classical and Advanced Approaches

A review of methods applicable to the study of masonry historical construction, encompassing both classical and advanced ones, is presented. Firstly, the paper offers a discussion on the main challenges posed by historical structures and the desirable conditions that approaches oriented to the modeling and analysis of this type of structures should accomplish. Secondly, the main available methods which are actually used for study masonry historical structures are referred to and discussed. The main available strategies, including limit analysis, simplified methods, FEM macro- or micro-modeling and discrete element methods (DEM) are considered with regard to their realism, computer efficiency, data availability and real applicability to large structures. A set of final considerations are offered on the real possibility of carrying out realistic analysis of complex historic masonry structures. In spite of the modern developments, the study of historical buildings is still facing significant difficulties linked to computational effort, possibility of input data acquisition and limited realism of methods

A localized mapped damage model for orthotropic materials

This paper presents an implicit orthotropic model based on the Continuum Damage Mechanics isotropic models. A mapping relationship is established between the behaviour of the anisotropic material and that of an isotropic one. The proposed model is used to simulate the failure loci of common orthotropic materials, such as masonry, fibre-reinforced composites and wood. The damage model is combined with a crack-tracking technique to reproduce the propagation of localized cracks in the discrete FE problem. The proposed numerical model is used to simulate the mixed mode fracture in masonry members with different orientations of the brick layers

Numerical Simulation of Traditional Timber-Masonry Buildings Subjected to Lateral Loads

Existing heritage buildings are often composed of diverse structural typologies, representing a challenge for structural analysis. This work investigates the use of nonlinear static analysis to assess the seismic behaviour of hybrid timber-masonry buildings. The proposed methodology includes the use of Lumped Plasticity Models (LPM) and Macro-Mechanical Finite Element (FE) approaches to simulate the response of structures composed of timber frames and masonry walls. Benchmark experiments on timber and masonry specimens subjected to lateral loads are used to calibrate the constitutive laws governing the behaviour of the proposed models. The calibrated models are used to appraise the seismic response of an existing timber-masonry building located in the historical centre of Valparaíso (Chile). The results predict the nonlinear acceleration-displacement capacity of the buildings, as well as the expected damage of the structure, revealing the potential local and global failure mechanisms

Viscoelasticity and damage model for creep behaviour of historical masonry structures

This paper presents a continuum model for the simulation of the viscous effects and the long-term damage accumulation in masonry structures. The rheological model is based on a generalized Maxwell chain representation with a constitutive law utilizing a limited number of internal variables. Thanks to its computational efficiency, this approach is suitable for the analysis of large and complex structures. In the paper, the viscous and damage models are presented and their coupling is discussed. The FE simulation of the construction process of the representative bay of Mallorca Cathedral is presented, together with the analysis of the long-term effects. The parameters of the model are tentatively calibrated on the basis of the time-dependent viscous deformations detected during the cathedral monitoring

Seismic Vulnerability Assessment of Representative Building Typologies from Barcelona‘s Eixample District

Unreinforced masonry buildings prevail in many old historical centres and urban areas worldwide. These structures may present inadequate seismic performance because they were often designed without considering any seismic resistance requirements. Therefore, they may be highly vulnerable and susceptible to damage caused by earthquakes, even of low intensity. This work investigates the seismic vulnerability of typical unreinforced masonry buildings situated in the Eixample district of Barcelona, Spain. Most of the buildings of the district were designed only for vertical static loads with slender load-bearing masonry walls and flexible diaphragms. A typical characteristic is the presence of openings with considerable size on the facades. The identification of the main parameters affecting the structural behaviour under lateral loading is necessary to evaluate the seismic vulnerability. As a first step, a building taxonomy for the Eixample district has been prepared in order to classify the different building typologies by taking into account the influence of the structural features in the overall response. This typology classification serves two aims. The first aim is to empirically evaluate the vulnerability of each category. The second one is to provide the basis for creating a numerical model of a representative building and analyse its seismic performance. The main objective of this paper is to assess the seismic behaviour of a typical unreinforced masonry structure by means of nonlinear static analysis. For this purpose, a three-dimensional Finite Element model of a representative building has been prepared. Pushover analyses have been performed in two directions (parallel and perpendicular to the façades) aiming to identify the typical failure mechanisms and the seismic capacity. The performance of the representative building typology, with its typical heterogeneities and irregularities, is compared with that of a reference regular unreinforced masonry structure. Additionally, a parametric analysis is carried out to evaluate the different seismic response by adding more storeys in height. This work is the basis for future analyses devoted to large scale seismic vulnerability assessment of the most representative building typologies of the Eixample district

Clinical manifestations of a new alpha-1 antitrypsin genetic variant: Q0parma

Alpha-1 antitrypsin deficiency is an autosomal, codominant disorder caused by mutations of the SERPINA1 gene. Several mutations of SERPINA1 have been described associated with the development of pulmonary emphysema and/or chronic liver disease and cirrhosis. Here, we report a very rare PI*Q0parma variant identified for the first time in an Italian family originally from the city of Parma in Northern Italy

Shaking table tests and numerical analyses on a scaled dry-joint arch undergoing windowed sine pulses

The damages occurred during recent seismic events have emphasised the vulnerability of vaulted masonry structures, one of the most representative elements of worldwide cultural heritage. Although a certain consensus has been reached regarding the static behaviour of masonry arches, still more efforts are requested to investigate their dynamic behaviour. In this regard, the present paper aims to investigate the performance of a scaled dry-joint arch undergoing windowed sine pulses. A feature tracking based measuring technique was employed to evaluate the displacement of selected points, shading light on the failure mechanisms and gathering data for the calibration of the numerical model. This was built according to a micro-modelling approach of the finite element method, with voussoirs assumed very stiff and friction interface elements. Comparisons with existing literature are also stressed, together with comments about scale effects.This work was partly financed by FEDER funds through the Competitivity Factors Operational Programme-COMPETE and by national funds through FCT-Foundation for Science and Technology within the scope of the Project POCI-01-0145-FEDER-007633.info:eu-repo/semantics/publishedVersio

Influence of geometry of cylindrical samples in the mechanical characterization of existing brickwork

The mechanical characterization of masonry is of paramount importance for the structural assess-ment of historical constructions against both vertical and horizontal actions. In particular, the compressive strength of masonry is normally regarded as a critical parameter for structural analysis. However, an accurate determination of the mechanical properties of masonry is a difficult task due to the complex and heterogene-ous behavior of the material. The mechanical characterization of historical masonry is also hindered by the need to limit damage caused by inspection in culturally valuable buildings. Recent researches and standards point to the possibility of estimating the compressive strength of existing brickwork by testing cylindrical samples of at least 150 mm diameter extracted from the brickwork walls. This work investigates the possibility of carrying out similar tests on smaller diameter cylinders. Using smaller cyl-inders may allow the extraction of a larger amount of samples and also permit the reduction of the extent of damage caused to the building. This study presents a comparison between compression tests performed on 150 mm and 90 mm diameter cy-lindrical samples to evaluate the strength and stiffness of masonry consisting of lime mortar and clay bricks. The tests were carried out in the laboratory on samples extracted from masonry walls by using a dry core-drilling procedure and then regularized with high strength mortar caps. The experimental results show the re-lationship between the different geometries of core samples regarding strength values, failure modes and crack patterns. The study contributes to the application of experimental tests on cylindrical samples as a minor de-structive technique to estimate the mechanical parameters of historical brickwork under compression.Postprint (published version