10 research outputs found
In-plane frictional resistances in dry block masonry walls and rocking-sliding failure modes revisited and experimentally validated
No full textThis paper presents new findings in the assessment of the lateral strength of dry block masonry walls under in-plane loading, based on an existing macro-modelling approach using limit analysis methods. The evaluation of the in-plane frictional resistances activated at the onset of the rocking-sliding mechanisms is revisited and two equivalent formulations accounting for the self weight of the wall and additional loads are presented. The accuracy and robustness of the analytical results are assessed by experimentally testing both the resultant frictional resistances and their applications points. The solution procedure of the previous macro-block model providing upper and lower bounds for the ultimate load factor is also reconsidered and the computation of the “exact” load factor falling within the range is proposed. A satisfactory comparison is found with a micro-block and other macro-block models existing in the literature. This comparison is carried out through a parametric analysis, in terms of both the load factor and the failure mode and with reference to the effects of chosen parameters (wall aspect, unit aspect, unit size ratios and overload) on the load factor
Corner failure in masonry buildings: An updated macro-modeling approach with frictional resistances
No full textThe failure mode of a free corner in masonry buildings, still poorly investigated, is one of the most common failure mechanisms occurring and clearly recognizable in the aftermath of a seismic event. It is characterized by the formation of a masonry wedge, mainly due to the thrust of roof elements in addition to inertial forces, and it generally involves rocking-sliding motions along the cracks on the interlocked orthogonal walls. The onset of this failure mode is herein analyzed by means of an upgraded macro-block model, based on the kinematic approach of limit analysis and accounting for the influence of frictional resistances on the collapse load multiplier and the related crack pattern. An original criterion weighting the role of rocking vs. sliding motion on the collapse load factor is developed and a formulation with general applicability is obtained. Several parametric analyses are performed in order to highlight the influence of geometrical, mechanical and loading parameters (with and without openings) on the seismic capacity of the corner. The reliability of the proposed model and solution procedure is confirmed through the comparison with the results provided by other macro-block models existing in the literature. The final perspective is the next implementation of the proposed model in FaMIVE (Failure Mechanism Identification and Vulnerability Evaluation) applicative
Management of multi-source information to identify the typology of the horizontal structures in historical masonry buildings: The case study of the museum of capodimonte in Naples (Italy)
No full textThe evaluation of the seismic safety of ancient masonry buildings usually requires compounding the need of preservation of the historical values with the need of achieving a proper level of knowledge of the parameters influencing their structural behaviour. To this aim, non-destructive techniques of instrumental investigation have lately attracted increasing attention, although the provided data are frequently not exhaustive and require to be integrated with different sources of information, such as historical documents and hypotheses of critical interpretation. Therefore, the management of this multi-source information is a crucial aspect in defining a methodological approach to the structural evaluation of the cultural heritage. This paper describes an integrated approach developed in the framework of the Project on the seismic evaluation of the Museum of Capodimonte in Naples (Italy) with reference to the typological identification of the horizontal structures upon the first level of the building. The management of the data derived from the application of the infrared thermography, integrated with the information from the visual inspections, the architectural survey and the historic analysis, has allowed obtaining a complete characterization of the structures under study
Experimental Investigation on the Torsion-Shear Behaviour at the Interfaces of Interlocking Masonry Block Assemblages
No full textThis paper presents an experimental investigation on the initial shear (cohesion) and torsion-shear strengths at the interface of an interlocking masonry block. An interlocking block is a rigid unit with locks avoiding the block to slide. This improves the seismic response of dry jointed assemblages of masonry structures subjected to in-plane and out-of-plane loading. The experimental investigation is designed and carried out for the corrugated interface having one lock with rectangular cross section, i.e. the specimen is an interlocking unit composed of a main body and a lock located on the upper face of the main body. Cement-based mortars are selected to reproduce the specimen, casted using a mould provided by a 3D printer, and both the lock and the main body are kept rigid during the tests. The initial shear and torsion-shear capacities of the interface at which the lock is connected to the main body are assessed together with its quasi-brittle fracture and registered in terms of load-displacement curves. In the designed setup, the horizontal force is applied to the rigid lock until it is disjointed from the rigid main body of the block, while the effect of rocking during the shear test is avoided. The force and the displacements are measured using a load cell and Linear Variable Displacement Transducers (LVDTs), respectively. The experimental programme includes four different sets with different load application points and different load directions, each set repeated on a number of similar specimens. Empirical formulations between the initial shear and compressive strengths of the lock interface are also evaluated
STRUCTURAL ASSESSMENT OF SANTA MARIA MADDALENA CHURCH IN ISCHIA ISLAND (ITALY) BY EXPERIMENTAL MODAL ANALYSIS UNDER OPERATIONAL CONDITIONS
No full textDuring the seismic event of 21st August 2017 in Ischia, many masonry churches were damaged. Within the inspected damaged churches, a very interesting case study is represented by Santa Maria Maddalena church, located on the hill of Casamicciola Terme, near to the epicentre. The church of Santa Maria Maddalena can be considered a ‘unicum’, since it was built in 1896, after the catastrophic earthquake of 1883, with a ‘mixed’ structure made mainly of yellow tuff blocks walls strengthened by iron profiles or wooden elements. Several examples of structures made of masonry walls with wooden elements embedded in the wall thickness, i.e. the so called ‘baraccato system’ are present in the island, while the use of iron profiles is rare. The paper is firstly aimed to present the results of detailed historical investigation, geometrical survey, damage status analysis and provisional safety assessment after the earthquake of 21st August 2017. These activities were carried out in collaboration with the Campania Regional Directorate for Cultural Heritage (MiBACT). Within such a collaboration, an in situ dynamic test was also performed under operational conditions. The set-up and the results of this test are here presented in order to point out the main features of the structural system in terms of relevant modal parameters, both at global and local level
Upgraded formulations for the onset of local mechanisms in multi-storey masonry buildings using limit analysis
No full textUnreinforced stone masonry (URSM) buildings without a box-like behaviour are very vulnerable to out-of-plane failure modes in seismic prone areas. These may involve partial or total collapses of walls with severe civil protection implications in terms of hazard to people, structures, and road network in the surroundings. In this paper, an advanced macro-block model accounting for frictional resistances is used to calculate the onset load factors for two classes of local mechanisms in multi-storey URSM buildings: the rocking-sliding and the flexure mechanisms. Based on the application of the kinematic approach of limit analysis, the presented formulations are an upgrade of the load factors identified within the FaMIVE (Failure Mechanism Identification and Vulnerability Evaluation) procedure existing in the literature and developed by the last author. These take into account a revisited evaluation of the in-plane frictional forces for the rocking-sliding mechanisms and the torsion-shear-flexure interactions for the horizontal flexure mechanisms. Moreover, the position of the hinge along the height of the building is identified more accurately, since it can be found at the story level or between two storeys, depending on the accounted mechanism. Other innovative issues concern upgrades of the former formulations for the vertical and horizontal flexure mechanisms. The final perspective of the presented abacus of local mechanisms in multi-storey URSM buildings is the next implementation of the proposed formulations in the FaMIVE procedure, after a sensitivity analysis of the main physical and geometrical parameters affecting the “hierarchy” among the all possible mechanisms. The identification of the most probable mechanisms, through a comprehensive but at the same time relatively rapid assessment, can be very useful for civil protection purposes
The relevance of frictional resistances in out-of-plane mechanisms of block masonry structures
No full textIn the last decades increasing attention has been devoted to the problems of structural strengthening and repair for those historical buildings under threat from several risks, such as general decay, deterioration, earthquakes and other natural hazards. In particular, the lack of out-of-plane strength of masonry structures has been identified as the weak link in masonry seismic capacity, being a primary cause of failure in different forms. Within this framework the more recent studies in block masonry structures either with dry contacts or with connecting poor mortar have pointed out the great importance of the stabilising role of fric-tion between blocks interlocked. This topic is examined in this paper with reference to the out-of-plane be-haviour of a masonry wall, weakly connected to sidewalls, all arranged in a stretcher bond pattern and whose ability to carry load is dominated by friction and self weight. The frictional resistance due to the interlocking between orthogonal walls is compared to other extrinsic or intrinsic structural capacities, e.g. the effect of tie-rods and the frictional resistance due to the presence of a simply supported horizontal diaphragm. The sensitivity of the load multiplier to these strength parameters is investigated at the onset of the rocking mechanism. The results of the parametric analysis are obtained with reference to different combinations of loading conditions, including the detrimental effect of the static thrust of masonry vaults
In-plane Behaviour of an Iron-Framed Masonry Façade: Comparison between Different Modelling Strategies
No full textThe ‘baraccato’ system is a construction technique with genius earthquake resilient features, used for the reconstruction of the historical city centres in the South of Italy after the catastrophic events occurred in the 18th-19th centuries. A very interesting example of such a building typology is represented by the Church of Santa Maria Maddalena, located in the municipality of Casamicciola Terme of the Ischia Island and built in 1896, after the catastrophic earthquake of 1883. The church is characterized by a mixed ‘baraccato’ system mainly made of yellow tuff block masonry walls strengthened by iron profiles or wooden elements. The reduced damage suffered by the church after the seismic event of 21st August 2017 evidenced the good behaviour of such a mixed structural system, especially into avoiding out-of-plane mechanisms. The presence of the iron-framed system is even more challenging in the definition of the modelling strategies for the structural analysis of the church. Thus, the choice of an appropriate numerical strategy to be used for nonlinear simulation should be properly investigated since the interaction between the frame elements and the elements representing the masonry walls has to be considered. As a first step of the structural analysis of the whole church, the in-plane behaviour of the main façade of the Church of Santa Maria Maddalena is analysed in this paper, with the aim to evaluate the efficacy of different modelling strategies. In particular, the study considers different models according to Finite and Discrete Element strategies available within DIANA FEA [1] and 3DMacro [2] software, respectively. Non-linear static analyses are carried out by means of both software and the obtained results are compared and discussed with the aim of extending them to the study of the whole church
Long-term effects of bosentan therapy in adult patients with pulmonary arterial hypertension related to congenital heart disease (Eisenmenger physiology): safety, tolerability, clinical and haemodynamic impact
No full textFirst and second authors equally contributed to the study. The Corresponding Author has the right to grant on behalf of all authors and does grant on behalf of all authors, an exclusive licence (or non exclusive for government employees) on a worldwide basis to the BMJ Publishing Group Ltd and its Licensees to permit this article to be published in HEART editions and any other BMJPGL products to exploit all subsidiary rights, as set out in our licence (http://heart.bmjjournals.com/ifora/licence.pdf). Affiliation
Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry
No full textObjective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase 3 randomized trials. The EXPosurE Registry RiociguaT in patients with pulmonary hypertension (EXPERT) study was designed to monitor the long-term safety of riociguat in clinical practice. Methods: EXPERT was an international, multicenter, prospective, uncontrolled, non-interventional cohort study of patients treated with riociguat. Patients were followed for at least 1 year and up to 4 years from enrollment or until 30 days after stopping riociguat treatment. Primary safety outcomes were adverse events (AEs) and serious adverse events (SAEs) coded using Medical Dictionary for Regulatory Activities preferred terms and System Organ Classes version 21.0, collected during routine clinic visits and collated via case report forms. Results: In total, 956 patients with CTEPH were included in the analysis. The most common AEs in these patients were peripheral edema/edema (11.7%), dizziness (7.5%), right ventricular (RV)/cardiac failure (7.7%), and pneumonia (5.0%). The most common SAEs were RV/cardiac failure (7.4%), pneumonia (4.1%), dyspnea (3.6%), and syncope (2.5%). Exposure-adjusted rates of hemoptysis/pulmonary hemorrhage and hypotension were low and comparable to those in the long-term extension study of riociguat (Chronic Thromboembolic Pulmonary Hypertension Soluble Guanylate Cyclase–Stimulator Trial [CHEST-2]). Conclusion: Data from EXPERT show that in patients with CTEPH, the safety of riociguat in routine practice was consistent with the known safety profile of the drug, and no new safety concerns were identified. © 2020 The Author
