This paper describes a simplified methodology for the assessment of unreinforced masonry (URM) walls under out-of-plane two-way bending seismic action. The methodology involves a force-based check derived from the principle of virtual work. This check is proposed based on experimental observations of significant cracking resistance associated with two-way spanning URM walls, indicating methodologies considering such walls to be pre-cracked or to be non-laterally supported as overly conservative. The methodology incorporates several findings and developments from recent experimental campaigns: ranging from novel characterization tests on masonry couplets to incremental dynamic tests on full-scale buildings. Such incorporations include new formulation to calculate the torsional shear strength of a bed joint and accounting for possible changes in the boundary conditions of an OOP wall during dynamic loading. Testing standards as well as recommendations in several international guidelines for masonry structures addressing the input properties required to implement the proposed methodology are enlisted and reviewed. The methodology requires the definition of the period of vibration of the assessed URM walls, to calculate which plate theory based formulation is provided. Open research questions and potential avenues for further development of the methodology are ultimately highlighted.@en

In this paper, a dataset collecting the results of in-plane cyclic tests on unreinforced masonry piers, carried out within different research projects, is presented. The dataset includes brick and block walls with different materials, bed-and head-joint typologies, dimensions, boundary conditions and vertical applied loads. The development of such dataset aims at providing a tool for the improvement of the understanding and the evaluation of the main parameters that may influence and govern the lateral response of the URM piers under seismic excitation. A preliminary investigation on the in-plane lateral strength and displacement capacity, being two of the most significant parameters used in seismic analyses for the design and assessment of masonry buildings, has been proposed. The dataset, that already groups several specimens, is freely shared and might be continuously updated. This source of information of consistent and reliable test results represents a necessary step into the process of definition of shared rules within the scientific and technical community, in particular for the improvement of codified criteria, analytical and numerical models and testing procedures.@en

In the last two decades, the province of Groningen, located in the North-East of the Netherlands, has been subjected to an increasing number of earthquakes induced by gas extractions. The existing building stock is mainly composed by unreinforced masonry (URM) buildings not conceived to resist seismic loads. The need of reducing the vulnerability of these buildings by means of retrofit interventions, led to the development and adoption of a new guideline (NPR9998:2018). As regards the seismic assessment of URM buildings using nonlinear static analysis, the guideline includes significant differences with respect to Eurocode 8, which is adopted in other European countries. The more significant differences lay in the description of failure mechanisms and constitutive laws of piers and spandrels, in the identification of limit states and in the calculation of seismic demand. In the last years, the assessment and retrofit in the region has been carried out using software based on an equivalent-frame strategy: among these, the 3Muri software has been widely adopted. The solver of this program is the research software TREMURI. In this work, a new version of the solver adopted by the software 3Muri, complying with the requirements of the new Dutch guideline, was developed; the tool was then validated with simple examples. To illustrate the specificities of the new guideline, the seismic assessment of a building representative of one of the most widely diffused URM building typologies in the area was performed.@en

The lateral resistance represents one of the most significant wall parameters to be used in the seismic analyses for the design/assessment of masonry buildings. In this article, an investigation on in-plane lateral strength of URM piers has been proposed thorough a comparison between the results from codified criteria and the outcomes of several experimental in-plane cyclic tests on masonry walls. In this context, a new database collecting the results of in-plane cyclic tests on unreinforced masonry piers, carried out within different research projects, has been devel-oped. The database consists of walls with bricks and blocks with different masonry materials (clay, lightweight aerated concrete, AAC, calcium silicate), bed-and head-joint typologies, di-mensions, boundary conditions, vertical applied loads and horizontal loading history. This source of information of consistent and reliable test results represents a necessary step into the process of definition of shared rules in the European context.@en

Out-of-plane (OOP) mechanisms are one of the major causes of structural collapse in unreinforced masonry (URM) buildings as observed in recent as well as past seismic events. Among such failures, two-way bending mechanisms involving at least one restrained vertical edge constitute a very distinct majority. Nevertheless, very little research pertaining to such mechanisms can be found currently in literature. The paper takes a step forward in this topic through the execution and interpretation of dynamic tests on four full-scale single leaf and one full-scale cavity URM walls. Each tested full-scale specimen consisting of a OOP panel and two return walls, varying in terms of commonly encountered boundary conditions, applied overburden or the presence/absence of an opening. The specimens were subjected to sequences of incremental input motion till collapse and these results are presented in terms of deformed shapes, failure mechanisms and force-displacement hysteretic curves. State of the art analytical techniques based on the method of virtual work are applied to evaluate their reliability as simplified tools for assessing the behaviour of such wall subjected to OOP two-way bending excitation. The testing campaign resulted in all specimens exhibiting a rather brittle response, despite sustaining accelerations of 1 g without any damage.@en

This paper provides information related to the sensor measurements obtained from five different unreinforced masonry (URM) walls subjected to incremental dynamic shake-table tests at EUCENTRE, Pavia, Italy. This information has been made available to assist in the development and calibration of analytical and numerical models intended to simulate the out-of-plane (OOP) two-way bending response of URM walls. For further interpretation of the sensor recordings, and for a detailed discussion on the observed seismic performance of the specimens, the reader is referred to the article entitled “Experimental Response of URM Single Leaf and Cavity Walls in Out-Of-Plane Two-Way Bending Generated by Seismic Excitation” [1]. Videos documenting the failure of each specimen are also available on YouTube [2].@en

This data article provides experimental data obtained from the incremental dynamic shake-table testing of four single leaf unreinforced masonry (URM) walls constructed in Calcium Silicate (CS) bricks reported in “Two-way bending experimental response of URM walls subjected to combined horizontal and vertical seismic excitation” [1]. These walls were tested in the second phase of a larger experimental campaign addressing the out-of-plane (OOP) response of full-scale URM panels in two-way bending configurations at EUCENTRE, Pavia, Italy. Data corresponding to the first phase of testing for four single leaf and one cavity wall has already been made available through Tomassetti et al. [2] and the information necessary to interpret these results can be found in Graziotti et al. [3]. The walls of the tests reported in this data article were constructed in an intentionally weakened mortar but using the same Calcium Silicate (CS) bricks as Graziotti et al. [3]. The walls were also tested in boundary conditions that were not addressed in [3] and a specimen was also subjected to simultaneous horizontal OOP and vertical seismic excitation in one of the tests. Videos documenting the failure of specimens tested in both phases of the experimental campaign can be viewed online on YouTube [4].@en

In this paper, a database collecting the results of 188 in-plane cyclic tests on unreinforced masonry piers with bricks and blocks, constituted of different masonry materials, bed- and head-joint typologies, dimensions, boundary conditions, applied vertical loads and horizontal loading history, is presented. The database, which will be freely shared, is organized in eight sections regarding general information and reference, information on masonry type, units and mortar, information on masonry walls, test conditions, estimated lateral resistances, experimental results of the cyclic tests, parameters of the bilinear curves and drift capacities. A preliminary investigation on the in-plane displacement capacity of the walls is also proposed since it represents one of the main parameter to be used in the global seismic analyses for the design/assessment of masonry buildings. Particular attention has been dedicated to the evaluation of the displacement capacity at different limit states in relation with European codes. Although the database, at the present stage, already contains several specimens, it will be continuously updated since this source of information of consistent and reliable test results represents a necessary step into the process of definition of shared rules in the European context, with particular reference to the definition of specific performance limit states and related capacity models for the in-plane seismic response of structural masonry walls. Keywords: URM piers; bricks and blocks; in-plane cyclic tests; database; displacement capacity @en

This paper presents the results of incremental dynamic tests on full-scale unreinforced masonry (URM) walls constructed with an intentionally weakened mortar under two-way bending excitation in the out-of-plane (OOP) direction. A specimen was also subjected to simultaneous vertical and horizontal excitation. Walls were also tested in boundary conditions that have not been previously reported in the literature. Emphasis was placed on the development and interpretation of a characterisation test to estimate the torsional shear strength of bed-joints, a parameter of prime importance in the OOP two-way bending behaviour of URM walls. Analytical formulation to estimate the initial stiffness of walls based on the theory of plates is then proposed and validated. Being the first experimental campaign to address the dynamic OOP two-way bending response of full-scale URM wall panels provided the opportunity to propose simple yet mechanically rational methodologies with which both the peak force resistance as well as the displacement at which such resistance is attained can be easily estimated.@en

An experimental programme was conducted on six different batches of unreinforced masonry (URM) considering different unit-mortar combinations to study their behaviour under torsional shear. Experiments performed included a specific characterisation test to measure the torsional shear strength of URM bed joints. Dilatancy measurements during both direct and torsional shear testing of masonry were recorded. Refined finite element modelling was then performed to evaluate whether parameters evaluated from standardised direct shear tests on masonry triplets can be used to estimate the torsional shear strength of URM bed joints. A possible mechanism by which dilatancy can increase the torsional shear resistance of bed joints without affecting the external level of applied normal force is also presented. Based on both experimental and numerical findings, a rational mechanics based formula to evaluate the torsional shear strength of URM bed joints is proposed and validated. This formula represents an improvement on currently used empirical formulation correlating the torsional shear strength of a URM bed joint to their flexural tensile strength.@en

Damage observations from recent seismic events have confirmed that the activation of out-of-plane (OOP) local mechanisms is one of the major causes of structural collapse in unreinforced masonry (URM) buildings. Such failures are mostly due to the attainment of displacement levels incompatible with equilibrium configurations for the kinematic chain of the considered mechanism rather than the exceedance of stress capacity in structural elements. However, very little research can be found currently in literature regarding the two-way bending OOP failure mechanism of walls involving at least one restrained vertical edge despite it being one of the most commonly reported and surveyed cause of structural damage. The paper takes a step towards addressing this lack of knowledge in the form of dynamic testing of full-scale URM masonry walls. In particular, results of three of these tests are reported in this paper: a test on a specimen representing the calcium silicate inner/loadbearing wall, a test representing the clay outer wall, and a cavity wall composed of both leaves together.@en

A non-linear discrete homogenized strategy is used to reproduce out-of-plane two-way bending shake table tests on full-scale unreinforced masonry walls. The numerical strategy represents unreinforced masonry walls as an assemblage of rigid quadrilateral plates connected through non-linear interfaces represented. The material response laws for these non-linear interfaces are derived from a homogenization procedure performed at the meso-scale by a finite-element plate model. This discrete model can simulate masonry orthotropy, full softening behaviour and failure. Bending and torsional deformation modes are represented. The performance of the numerical models in describing the response of the experimentally tested full-scale specimens is presented. The numerical strategy is then used to study the behaviour of unreinforced masonry walls in configurations hitherto untested. Such numerical results are then compared to state-of-the-art analytical approaches. Potential avenues of improvement for the implemented analytical methods are also highlighted.@en