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This paper presents the results of experimental tests on reduced-scale models of multistory masonry buildings with rigid floors. The laboratory investigation includes pushover tests of the aforementioned buildings and quasi-static, monotonic and cyclic tests of basic elements (panels and columns) of common masonry structures. Such tests highlight a noticeable inelastic behavior of the masonry and, consequently, an appreciable ductility of the models. The presented laboratory experimentation does not allow an immediate extension of the experimental results to the behavior of actual structures, but it qualitatively highlights the investigated phenomenon. Furthermore, it allows the verification of the reliability of the numerical results provided by the non-linear theoretical models developed by researchers in recent years

In the current paper, the experimental investigation of an innovative solution based on the use of slender steel shear panels for seismic upgrading of existing reinforced concrete frames is presented. Based on a preliminary experimental evaluation of the performance of the bare r.c. structure, an ad hoc design procedure has been developed in the framework of the performance based design methodology. Therefore, the steel panel configuration arrangement has been defined according to a simplified analytical procedure and then checked by adopting a sophisticated FEM model. Finally, after the global numerical analyses of the whole system, the full-scale test of the upgraded structure has been carried out, confirming the effectiveness of the adopted retrofitting device.

This paper deals with a critical analysis of the current seismic design criteria provided by Eurocode 8 for Moment Resisting Frames. This approach is based on the capacity design principle, in which the design is governed by the strength and stability of the structural elements and by hierarchy ofstrength, this in order to allows development of high dissipative collapse mechanism. The drawbacks of this approach is that the maximum required inter-storey drifts, at service limit states, are not directly satisfied. This leads to an enlargement of geometrical dimensions of the elements, producing significant over-strength and nullifying the use of high behaviour factors. In this paper, an alternative design criterion is proposed. According to this the design is governed by maximum inter-storey drift at service limit state, whereas the satisfaction of capacity design rules is contextually verified. This means to design the structure with seismic actions corresponding toservice earthquakes (i.e. unitary q-factor). Linear and non-linear static analyses on 3, 6 and 9-storey steel frames were performed to compare the design methodologies in terms of push-over curves (i.e.over-strength), interstorey- drifts and collapse mechanisms. Furthermore, the effect of panel zone on the global seismic response of frames was taken into accountin the performed analyses. It has been properly modelled using one of the most diffused literature model, the so called Krawinkler's 'frame model', accounting both its elastic and plastic behaviour.

Seismic capacity assessment of existing buildings is of paramount importance for mitigating the seismic risk in earthquake-prone areas. In Europe, the next version of Eurocode 8 and the current version of the Italian standards suggest the adoption of both linear and nonlinear approaches to perform seismic analyses of existing masonry buildings. This paper discusses with the main issues concerning linear and nonlinear analyses methodologies provided by the Italian standards for existing unreinforced masonry buildings. An historical building located in Southern Italy, representative of the Mediterranean basin buildings, has been chosen as a case study and modelled through the equivalent frame model. According to the Italian standards, the influence of in-plane stiffness of floors and spandrels on the overall seismic capacity of the structure has been considered in the analyses. Beyond the code prescriptions, the effect of different ultimate drifts values assumed for the spandrels on nonlinear behavior of the structure has been analysed. The results of two types of linear analyses (lateral static force method and modal response spectrum analysis) have been compared among them and with those provided by the nonlinear static method. Conclusions show that either behavior and overstrength factors provided by the Italian standards are conservative than those estimated through the nonlinear static analyses. Moreover, it has been remarked that the value of ultimate drift adopted for the spandrel can affect significantly the nonlinear response of the structures, although this topic still represents an open issue.

This paper presents a benchmark exercise for the seismic assessment of unreinforced masonry (URM) buildings as a follow-up of a blind prediction test organized in the context of the European Conference of Earthquake Engineering Series. The blind prediction exercise was aimed at better defining the open issues in current procedures for modeling and performing seismic analysis of URM buildings, by highlighting the uncertainty that can influence the results. This work presents an overview of the approaches used by different research teams and the scope of predictions. The benchmark structure was a three-story building with traditional European architecture from which two Cases were considered: A) stone masonry walls and flexible horizontal diaphragms and B) brick masonry walls and rigid horizontal diaphragms. A wide range of approaches was used by the participating teams concerning modeling strategies, methods of analysis and criteria for the attainment of limit states, which are here addressed as potential sources for the dispersion of predictions. The results were compared in terms of capacity curves, predicted failure mechanisms compatible with the fulfillment of limit states of near collapse and damage limitation, and related minimum values of peak ground acceleration (PGA). The results show an overall good agreement for damage patterns and collapse mechanisms in both benchmark structures, presenting some differences in the type of failure mode and its extent. However, the scatter of predicted capacity curves and critical PGAs is very high, especially for the Case with brick masonry and rigid diaphragms, indicating that clearer procedures in the building codes are required for professionals., This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020.

In-plane seismic behaviour of Cross-Laminated Timber (CLT) walls is influenced by panel-to-panel and panel-to-foundation mechanical connections, which consist of hold-downs and angle brackets. Due to the platform constructional technology, the orthogonal to grain timber-to-timber contact is also involved in the seismic response of the panels. To date, literature theoretical approaches to evaluating the flexural load-bearing capacity of CLT panels focus their attention on the schematization of hold-downs and angle brackets only, under evaluating the role of timber compressed in the perpendicular direction. In this paper the influence of orthogonal to grain timber properties on the overall seismic behaviour of CLT walls has been investigated, proposing a general theoretical model to schematize the panel-to-panel and panel-to-foundation connections. A parabola-rectangle constitutive behaviour has been defined to describe the orthogonal to grain timber behaviour in the connection zones, while hold-downs and angle brackets are modelled adopting literature models. Five different failure conditions, described by mathematical formulations, able to describe the entire axial force-bending moment interaction domain have been defined. The proposed model has also been employed to schematize the connection zones in multi-storey CLT walls with openings, allowing to investigate the effect of the orthogonal to grain properties on its seismic behaviour. Results of nonlinear analyses demonstrate a significant influence of orthogonal to grain timber properties on seismic behaviour of the walls, affecting their strength, stiffness, ductility and collapse mechanisms.

The whole Mediterranean area historical heritage is mostly constituted by 'ancient' unreinforced masonry constructions which are particularly vulnerable to earthquakes. Due to the particular attitude to out-of-plane collapse mechanisms, 'ancient' constructions largely contribute to increase the seismic risk. In this paper, a methodology for retrofitting unreinforced masonry buildings, aimed to gradually transforms the 'ancient' masonry building into a 'modern' code-conforming building, is proposed. This approach has been applied to an existing masonry building located near L'Aquila (Italy) and damaged during the 2009 earthquake. The results demonstrate the usefulness of a methodological approach to implement retrofitting actions. Thus, appears more easily to calibrate the interventions as a function of the structural weakness and to quantify the role of each intervention in terms of capacity-to-demand ratio. Moreover, a gradual control of the seismic performance enhancement with respect to the original capacity can be achieved, avoiding high economic costs related to unnecessary interventions.

This paper deals with the influence of the rolling shear deformation on the flexural behavior of CLT (Cross-Laminated Timber) panels. The morphological configuration of the panels, which consist of orthogonal overlapped layers of boards, led to a particular shear behavior when subjected to out-of-plane loadings: the low value of the shear modulus in orthogonal to grain direction (i.e., rolling shear modulus) gives rise to significant shear deformations in the transverse layers of boards, whose grains direction is perpendicular with respect to the tangential stresses direction. This produces increases of deflections and vibrations under service loads, creating discomfort for the users. Different analytical methods accounting for this phenomenon have been already developed and presented in literature. Comparative analyses among the results provided by some of these methods have been carried out in the present paper and the influence of the rolling shear deformations, with reference to different span-to-depth (L/H) ratios investigated. Moreover, the analytical results have also been compared with those obtained by more accurate 2D finite element models. The results show that, at the service limit states, the influence of the rolling shear can be significant when the aspect ratios became less than L/H = 30, and the phenomenon must be accurately considered in both deflection and stress analysis of CLT floors. Contrariwise, in the case of higher aspect ratios (slender panels), the deflections and stresses can be evaluated neglecting the rolling shear influence, assuming the layers of boards as fully-connected.

In this paper the results of a wide experimental campaign on the structural behaviour of ancient chestnut beams are presented. The beams were taken from the floor slab of an existing building, they being representative of the bearing structures of common historical buildings of many Mediterranean countries. Therefore, they were characterized by natural defects and degradation phenomena, which may have a significant effect on the evaluation of the load bearing capacity of the member. Four beams in actual dimension have been considered, which have been subjected to static bending tests, aimed at the evaluation of stiffness, strength, post-elastic behaviour and collapse mechanism. In the paper, the global influence of relevant defect patterns on the behaviour of these beams has been evaluated by comparing their overall behaviour with the actual material response obtained by compression, bending and shear tests on defect-free small specimens. The obtained results show that the simplified methods commonly used to evaluate the bearing capacity of wooden beams can be safely applied to ancient structural members as well, provided that adequate reduction factors for the shear resistance are considered.

The refurbishment of ancient timber structures requires an acquaintance of the residual structural capacity of members in order to design reliable repairing interventions. Such information cannot be obtained by means of destructive tests on sacrificial elements extracted from the existing structures, while non-destructive tests (NDT) are currently performed in situ on timber elements. In this article, a methodology based on resistographic NDTs is analysed. In particular, an experimental campaign of NDTs on ancient chestnut elements has been carried out for determining a correlation between NDT results and mechanical wood properties, previously obtained by means of destructive tests. Then, a numerical formulation between resistographic tests carried out along the direction parallel to the grain and the longitudinal ultimate compressive stress has been proposed. In addition, since in situ NDTs can be performed only along direction transversal to the growth rings, a correlation between longitudinal and transversal NDTs has been obtained. Finally, in order to validate the proposed procedures, a series of analogous tests have been carried out also on new spruce elements.

European Timber Buildings as an Expression of Technological and Technical Cultures, ELSEVIER, 2002