Low unit strength masonry: computational modelling approaches

Masonry is characterized by the large variability of its components. Parameters like strength, bond and workmanship defects strongly influence the performance of the overall structure. The applicability of different computational modelling approaches to assess the structural behaviour of masonry has been studied. Two of the most relevant computational modelling approaches have been considered namely: finite element method (FEM) and distinct element method (DEM). In order to validate the numerical outcomes, comparisons with the experimental results have been undertaken. The aim of this paper is to contribute to the knowledge and selection of a suitable modelling approach for modelling low unit strength masonry structures. The results showed that in the case of low unit strength masonry, FEM is a more suitable approach to use. In fact, since in the considered case, the block is the weak component, it is not possible to assume the brick units as a rigid block. Therefore an accurate plasticity and cracking model for the brick is required

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

Repair of composite-to-masonry bond using flexible matrix

The paper presents an experimental investigation on an innovative repair method, in which composite reinforcements, after debonding, are re-bonded to the substrate using a highly deformable polymer. In order to assess the effectiveness of this solution, shear bond tests were carried out on brick and masonry substrates within two Round Robin Test series organized within the RILEM TC 250-CSM: Composites for Sustainable strengthening of Masonry. Five laboratories from Italy, Poland and Portugal were involved. The shear bond performance of the reinforcement systems before and after repair were compared in terms of ultimate loads, load-displacement curves and strain distributions. The results showed that the proposed repair method may provide higher strength and ductility than stiff epoxy resins, making it an effective and cost efficient technique for several perspective structural applications

Percutaneous treatment of patients with heart diseases: selection, guidance and follow-up. A review

Aortic stenosis and mitral regurgitation, patent foramen ovale, interatrial septal defect, atrial fibrillation and perivalvular leak, are now amenable to percutaneous treatment. These percutaneous procedures require the use of Transthoracic (TTE), Transesophageal (TEE) and/or Intracardiac echocardiography (ICE). This paper provides an overview of the different percutaneous interventions, trying to provide a systematic and comprehensive approach for selection, guidance and follow-up of patients undergoing these procedures, illustrating the key role of 2D echocardiography

No evidence of association between prothrombotic gene polymorphisms and the development of acute myocardial infarction at a young age

Background : we investigated the association between 9 polymorphisms of genes encoding hemostasis factors and myocardial infarction in a large sample of young patients chosen because they have less coronary atherosclerosis than older patients, and thus their disease is more likely to be related to a genetic predisposition to a prothrombotic state Methods and Results : this nationwide case-control study involved 1210 patients who had survived a first myocardial infarction at an age of 45 years who underwent coronary arteriography in 125 coronary care units and 1210 healthy subjects matched for age, sex, and geographical origin. None of the 9 polymorphisms of genes encoding proteins involved in coagulation (G-455A -fibrinogen: OR, 1.0; CI, 0.8 to 1.2; G1691A factor V: OR, 1.1; CI, 0.6 to 2.1; G20210A factor II: OR, 1.0; CI, 0.5 to 1.9; and G10976A factor VII: OR, 1.0; CI, 0.8 to 1.3), platelet function (C807T glycoprotein Ia: OR, 1.1; CI, 0.9 to 1.3; and C1565T glycoprotein IIIa: OR, 0.9; CI, 0.8 to 1.2), fibrinolysis (G185T factor XIII: OR, 1.2; CI, 0.9 to 1.6; and 4G/5G plasminogen activator inhibitor type 1: OR, 0.9; CI, 0.7 to 1.2), or homocysteine metabolism (C677T methylenetetrahydrofolate reductase: OR, 0.9; CI, 0.8 to 1.1) were associated with an increased or decreased risk of myocardial infarction Conclusions : this study provides no evidence supporting an association between 9 polymorphisms of genes encoding proteins involved in hemostasis and the occurrence of premature myocardial infarction or protection against it

Discrete element modelling of the archaeological colonnade in Pompeii

In this paper the seismic vulnerability analysis of a magnum opus of the architectural heritage residing in the ancient city of Pompeii in Italy is presented. Pompeii is a Roman city destroyed during a catastrophic eruption of the Vesuvius volcano in 79 a.C.. Nowadays, Pompeii is one of the biggest tourist sites in Southern Italy and since 1997 it is a UNESCO world heritage site. During its life, the city suffered many earthquakes, and the ruins of the ancient city show several partially collapsed buildings. The peculiarity of the analysed colonnade is an “innovative solution” adopted to avoid long span beams over its slender columns: short segments were built up providing opposing inclined patterned edges. Distinct element analyses outcomes are discussed to evaluate the current seismic vulnerability of the colonnade, in order to preserve the safety of the structure and to study the effects of degradation of the archaeological material

Finite Element Modelling of the Archaeological Colonnade in Pompeii

In this paper, the seismic behaviour of an archaeological monumental colonnade under earthquake actions is examined through planar numerical simulations (nonlinear finite element analyses). The colonnade has two storeys with multi-drum columns and multi-blocks segmented trabeations. The scope of the analyses is to improve the knowledge on the structural behaviour of the innovative solution of segmented trabeation adopted in the ancient era for this colonnade and to evaluate the added vulnerability related to the effects of water leakage and pollutants in between the stone blocks of the structure as a result of the current degradation. The ancient city of Pompeii in Italy, is a partially buried Roman town-city; after suffering many earthquakes in the past it was destroyed during a long catastrophic eruption of the Vesuvius volcano in 79 A.D. and remained covered until its accidental rediscovery in 1749. Nowadays, the ruins of the ancient town present many partially collapsed buildings, not only as a result of other earthquakes during the last three centuries, but also as a consequence of rapid degradation of the archaeological material. Numerical analyses show the seismic vulnerability of a colonnade, in order to understand how a UNESCO World cultural heritage site can be preserved, avoiding risks for cultural heritage and human life

Restraining bars buckling by means of FRP wrapping: an analytical approach

Internal transverse steel reinforcements (e.g. stirrups) are the main internal devices that avoid the longitudinal steel bars buckling, but in most of all existing RC structures the quantity and the spacing between steel stirrups are inadequate. In these structures longitudinal bars buckling can be avoided by applying external reinforcement, in particular, by means of Fibre Reinforced Polymer (FRP) wrapping. A novel analytical approach for the study of longitudinal bars buckling in column wrapped with FRP is proposed. longitudinal bars has been considered as axially loaded beam, while the mechanical effect of FRP wrapping on the bars has been modelled by means of springs. The effect of elastic and inelastic behaviour has been taken into account by means of the reduced modulus theory. The well-known relations for steel stirrups has been extended to the case of FRP wrapping to propose an analytical formulation, valid both for circular and noncircular column cross sections, for the evaluation of the FRP thickness needed to avoid the longitudinal bars buckling

Evaluation of different computational modelling strategies for the analysis of low strength masonry structures

Masonry is a composite material characterized by a large variability of its constituent materials. The materials used, the quality of the bond and variations in the standard of workmanship significantly affect the mechanical performance of the overall masonry structure. Masonry structures, especially the historical ones, are usually characterized by low strength, due to a variety of reasons, namely low units and/or mortar strength or low bond; this makes more difficult to study these types of structures according to general rules because of different structural schemes. The aim of this paper is to evaluate the suitability of continuous FEM (Finite Element Method) or discrete DEM (Distinct Element Method) approaches to analyse the behaviour of low strength masonry and to contribute to the knowledge and selection of the best approach with a cost and time effective solution. The comparison with experimental results on different low strength masonry validated the approaches and showed that, for low bond strength masonry, DEM approaches performed better compared to low unit strength masonry where the emphasis on joint behaviour in DEM approaches is less effective because the weak component is the unit