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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 the results of an experimental program conducted on H-shaped reduced-scale reinforced masonry spandrels subjected to monotonic loadings. It summarized tests units, test set-up and experimental results relative to seventeen samples reinforced by thin-steel stripes arranged with different configurations, and compared with those unreinforced. The first configuration comprised masonry spandrels strengthened by unbonded horizontal and diagonal steel stripes (i.e., stripes connected by means of threaded rods to the nodal area of the panel), while the second masonry spandrels reinforced by bonded horizontal stripes (i.e., stripes connected with 5 or 13 threaded rods over the spandrel length). For each reinforcement configuration, slender, intermediate and squat slenderness ratios have been considered for the samples. The conducted research investigated the effectiveness of the reinforcement to enhance the seismic response of the spandrels. Test results demonstrated that the application of steel stripes is beneficial in changing the failure modes from shear-dominated into flexural-dominated, especially for intermediate and squat panels prone to brittle shear mechanisms. Despite that increases of strength are reduced with respect to unreinforced samples, when reinforced the post-peak response changes significantly being it characterized by a remarkable ductile response for whatever spandrels’ slenderness ratios.

This paper deals with the experimental monotonic and cyclic behavior of masonry spandrels reinforced with Fiber Reinforced Polymers (FRP). The research is a part of a wider program, started by the authors in the last decade, regarding the analysis of the seismic behavior of masonry spandrels in historical buildings of the Mediterranean area. The paper summarizes the properties of the test units, the test set-up and the results of the experimental monotonic and cyclic behavior conducted on twenty-four scaled down H-shaped spandrels made with homogeneous material (e.g. mortar with low tensile strength). Both unreinforced and FRP-reinforced specimens with three different slenderness ratios – e.g. slender, intermediate and squat – and three different arrangements of FRP laminates have been considered for the tests. The main objective has been to verify the possibility of preventing brittle failure modes, typical of spandrels subjected to in-plane seismic actions (e.g. diagonal cracking), and of increasing their strength by applying specific reinforcement systems, so encouraging more ductile behavior characterized by toe-crushing at the ends of the spandrels itself.

The interest of the scientific community for the seismic behaviour of existing masonry buildings is continuously increasing in recent years. The authors have analysed the structural behaviour of spandrels in URM buildings by means of several experimental tests performed on specimens in reduced scale. The results of this experimental campaign are reported in this paper and are compared with the results of several experimental tests on full scale masonry spandrels available in literature. The key-data and the set-up of the tests, the criteria adopted for testing and the results obtained are discussed, in order to underline their effectiveness in defining a theoretical interpretation of the actual mechanical behaviour of spandrels in masonry buildings subjected to seismic actions. Then, some of the tests have been simulated by means of FE models. The comparison between experimental and numerical results shows sensible variation depending on the material modelling and the geometrical properties of the panels.

In this paper, a simplified theoretical model (named 'the arched strut'), useful for the evaluation of the structural behaviour of masonry spandrels subjected to shear, is proposed. It has been defined on the basis of the results of both numerical and experimental analyses performed on reduced scale specimens. The numerical analysis has been carried out in order to obtain confirmation of the collapse mechanisms observed during the experiments and information which cannot be directly obtained from testing and is difficult to obtain theoretically too, such as the extension of the effective area at the edges of the panel and the value of the horizontal component of the force acting in the strut. By means of the proposed model, theoretical expressions corresponding to the different observed failure mechanisms (toe-crushing and tension cracking) have been formulated. Finally, both experimental and theoretical findings have been compared with the Italian code requirements.