Out-of-plane seismic response of stone masonry walls: experimental and analytical study of real piers

This paper presents the application of an existing simplified displacement-based procedure to the characterization of the nonlinear force-displacement relationship for the out-of-plane behaviour of unreinforced traditional masonry walls. According to this procedure, tri-linear models based on three different energy based criteria were constructed and confronted with three experimental tests on existing stone masonry constructions. Moreover, a brief introduction is presented regarding the main characteristics of the in situ cyclic testing recently carried out using distributed loads, as well as results obtained during the experimental campaigns performed. The comparison between the experimental and the analytical results are presented and discussed

Analytical and numerical seismic assessment of heritage masonry towers

Abstract The new Italian building code, published in 2018 [MIT in NTC 2018: D.M. del Ministero delle Infrastrutture e dei trasporti del 17/01/2018. Aggiornamento delle Norme Tecniche per le Costruzioni (in Italian), 2018], explicitly refers to the Italian “Guidelines for the assessment and mitigation of the seismic risk of the cultural heritage” [PCM in DPCM 2011: Direttiva del Presidente del Consiglio dei Ministri per valutazione e riduzione del rischio sismico del patrimonio culturale con riferimento alle norme tecniche per le costruzioni, G.U. n. 47 (in Italian), 2011] as a reliable source of guidance that can be employed for the vulnerability assessment of heritage buildings under seismic loads. According to these guidelines, three evaluation levels are introduced to analyse and assess the seismic capacity of historic masonry structures, namely: (1) simplified global static analyses; (2) kinematic analyses based on local collapse mechanisms, (3) detailed global analyses. Because of the complexity and the large variety of existing masonry typologies, which makes it particularly problematic to adopt a unique procedure for all existing structures, the guidelines provide different simplified analysis approaches for different structural configurations, e.g. churches, palaces, towers. Among the existing typologies of masonry structures there considered, this work aims to deepen validity, effectiveness and scope of application of the Italian guidelines with respect to heritage masonry towers. The three evaluation levels proposed by the guidelines are here compared by discussing the seismic risk assessment of a representative masonry tower: the Cugnanesi tower located in San Gimignano (Italy). The results show that global failure modes due to local stress concentrations cannot be identified if only simplified static and kinematic analyses are performed. Detailed global analyses are in fact generally needed for a reliable prediction of the seismic performance of such structures.</jats:p

Laboratory and numerical experimentation for masonry in compression

In this paper, the initial part of a laboratory and numerical experimental campaign dedicated to historical masonry is described. One leaf masonry panels with regular texture are built in order to simulate a historical material characterised by strong resisting elements and weak mortar joints. Laboratory tests are first dedicated to masonry components and then to the behaviour in compression of masonry panels, which is applied both orthogonal and parallel to bed joints, in order to highlight the orthotropic behaviour of the material. First of all, the mechanical parameters of masonry constituents are calibrated and then a heterogeneous finite element model is introduced and calibrated for reproducing the orthotropic behaviour of masonry, together with the initial elastic response and the initial nonlinear behaviour due to the first level of damage

Comparison of similitude laws applied to multi-storey masonry structures with flexible diaphragms

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Journal of Earthquake Engineering on 2022, available online at: http://www.tandfonline.com/10.1080/13632469.2022.2040655.The present paper discusses similitude laws employed for the shaking-table tests of masonry structures with flexible diaphragms. Two tasks are tackled. First, the paper presents a literature review on similitude laws. The discussion focuses on Cauchy and Cauchy-Froude laws. Second, numerical analysis is performed to examine the accuracy and adequacy of the aforementioned two laws. Two previously performed shaking-table tests are taken advantage of as the case studies. The paper explores the ideal applications of similitude laws to the shaking table tests of masonry structures with flexible diaphragms by comparing the behaviour between full-scale prototypes and reduced-scale models.Peer ReviewedPostprint (author's final draft

Numerical modelling of cavity wall metal ties

The assessment of the out-of-plane response of unreinforced masonry (URM) buildings with cavity walls has been a popular topic in regions such as Central and Northern Europe, Australia, New Zealand, China and several other countries. Cavity walls are particularly vulnerable as the out-of-plane capacity of each individual leaf is significantly smaller than the one of a solid wall. In the Netherlands, cavity walls are characterized by an inner load-bearing leaf of calcium silicate bricks, and by an outer veneer of clay bricks that has only aesthetic and insulation functions. The two leaves are typically connected by means of metallic ties. This paper utilizes the results of an experimental campaign conducted by the authors to calibrate a hysteretic model that represents the axial cyclic response of cavity wall tie connections. The proposed numerical model uses zero-length elements implemented in OpenSees with the Pinching4 constitutive model to account for the compression-tension cyclic behaviour of the ties. The numerical model is able to capture important aspects of the tie response such as the strength degradation, the unloading stiffness degradation and the pinching behaviour. The numerical modelling approach in this paper can be easily adopted by practitioner engineers who aim to model the wall ties more accurately when assessing the structures against earthquakes

Numerical investigation of the displacement incompatibility between masonry infill walls and surrounding reinforced concrete frames

In the European building practice, masonry infill panels have been widely adopted as facade elements in Reinforced Concrete (RC) frames in order to provide architectural needs such as thermal and acoustic insulation. During seismic shakings, infill wall panels and the surrounding RC frame have a strong interaction, potentially leading to local brittle failures of both structural and non-structural elements or even to global collapse mechanisms (e.g., soft-story mechanism). In the past years, a significant research effort has been dedicated at the international level to better understand the seismic performance of infilled RC frame structures as well as to develop suitable and practical design/retrofit techniques to reduce the negative effects of infill-frame interaction. However, past numerical and experimental investigations mainly focused on the diagonal compression strut mechanism and associated stress path. On the other hand, a procedure to assess the local infill-frame displacement incompatibility (i.e., detachment due to the relative deformation mechanism) in terms of shape and values is still missing in the literature. Therefore, this paper investigates and discusses the seismic displacement incompatibility between infill walls and the RC frame structure as well as the key parameters affecting the infill-frame detachment. Specifically, the concept of shape functions is introduced and proposed to assess the seismic infill-frame displacement incompatibility, in line with and extending the state-of-the-art investigations on the relative deformation mechanism between seismic-resisting frames and precast flooring units. The proposed methodology can support a displacement-compatible design check of specific connection solutions, in the form of either shear keys and/or steel dowels, as part of either strengthening or decoupling seismic retrofit strategies, as well as of energy rehabilitation solutions, such as external thermal insulation systems, in order to protect these components during earthquakes

Seismic assessment of the out-of-plane performance of traditional stone masonry walls

Tese de Doutoramento. Engenharia Civil. Faculdade de Engenharia. Universidade do Porto. 201

Alternative techniques and approaches for improving the seismic performance of masonry infills

This doctoral dissertation aims to report on the research work carried out in the field of alternative techniques and approaches for improving the seismic performance of masonry infills. An aspect often overlooked in the design and/or verification of Reinforced Concrete (RC) frame buildings it is the one related to the so-called "non-structural" elements, that are elements without a main structural function, but capable of causing damage to things and people during the seismic action. A typical example of non-structural elements are the external infills of RC frame buildings, which often have masses and stiffnesses able to significantly modify the behavior and response of the structure during the seismic action. Typically, the UnReinforced Masonry (URM) infill walls are made of single or double facing hollow bricks placed inside the meshes of RC frames. The main damage mechanisms observed in URM infill walls during seismic events include in the plane (IP) or out of the plane (OOP) damage mechanisms, both characterized by degradation of strength, stiffness and low energy dissipation. In this doctoral dissertation, the analysis of the influence of the in-plane and out-of-plane behavior of UnReinforced Masonry infill walls on global seismic performances of different RC frame buildings is presented. The research mainly focuses on: i) numerical investigation of the in- plane / out-of-plane interaction in order to evaluate its entity and severity pointing out the correct description of the damage scenarios; ii) identification of alternative intervention solutions, aimed at mitigating the phenomenon of overturning of the infill panels; iii) estimate of the expected economic losses. Rough cost-benefit analyses have been carried out in order to compare the sustainability of alternative seismic rehabilitation techniques, thus providing a rational base and objective criteria that can be used in the design and/or preliminary screening phase by insurance companies, to reduce the seismic risk and the impact of earthquakes on a community