In‐plane–out‐of‐plane non‐linear model of masonry infills in the seismic analysis of r.c.‐framed buildings

Abstract

Summary The out‐of‐plane (OOP) behaviour of masonry infills (MIs), inserted in reinforced concrete (r.c.)–framed buildings, is recognized as one of the most important failure modes of this nonstructural element during an earthquake, which may be a consequence of simultaneous or prior in‐plane (IP) damage. A five‐element macro‐model, with four diagonal OOP non‐linear beams and one horizontal IP non‐linear truss, with an equivalent mass of the infill panel divided between two central nodes, takes into account the IP and OOP failure modes occurring in the event of seismic loading. Pivot hysteretic models predict the non‐linear IP and OOP force‐displacement laws of the infill panel, based on geometrical rules defining loading and unloading branches. Firstly, a calibration of the proposed IP‐OOP interaction model of MIs is carried out considering full‐scale experimental results of traditional masonry typologies. Each specimen is initially subjected to in‐plane quasi‐static cyclic loading, until a maximum drift is reached, and then one‐sided OOP cycles are imposed pushing in the horizontal direction and back to zero force. Then a numerical investigation considers masonry infills of an existing six‐storey r.c.‐framed building designed in compliance with a former Italian seismic code. To evaluate the interaction, the results of simultaneous IP and OOP cyclic tests on MIs at the top, intermediate, and lowest levels of the test structure are presented, assuming different displacement histories: (1) OOP loading faster than IP, at the sixth storey; (2) equal IP and OOP loading, at the third storey; (3) IP loading faster than OOP, at the first storey. Finally, attention is focused on the contribution of masonry infills to the IP and OOP energy dissipation of r.c.‐framed structures.

A new macromodel for the assessment of the seismic response of infilled RC frames

“…More recently, some refined strut models have also been proposed to simulate the out-of-plane response of IRCFSs and the interaction between in-plane and out-of-plane responses of masonry infills. [35][36][37][38] To overcome some of the limits of the (in-plane) strut model, an alternative model of the infill was recently proposed by Caliò and Pantò 39 and denoted as discrete macro-element model (DMEM). In this latter proposal, the infill was simulated by means of a plane, geometrically consistent, mechanical model able to reproduce the non-linear behaviour of unreinforced masonry panels.…”

“…Nonetheless, often the proposed modifications appear unsuitable to be applied in a general view because based on empirical formulations obtained from a restricted number of laboratory tests. More recently, some refined strut models have also been proposed to simulate the out‐of‐plane response of IRCFSs and the interaction between in‐plane and out‐of‐plane responses of masonry infills …”

In-plane and out-of-plane seismic damage of masonry infills in existing r.c. structures: the case study of De Gasperi-Battaglia school in Norcia

“…where q u represents the OOP maximum capacity, in terms of pressure acting on the panel, while E eq and I eq are the equivalent elasticity modulus and moment of inertia assigned to the model: with k p obtained by imposing the equivalence of the stiffness between simply supported bi-diagonal beams and cracked plate (Mazza 2019a). The value of q u [kPa] is calculated through the empirical relations proposed by Dawe and Seah (1989), assuming that the panel is supported on four sides:…”

“…The OOP nonlinear behaviour of MIs and its interaction with the IP response are accounted for by using the model of Ricci et al (2017Ricci et al ( , 2018, in which V-shaped bidiagonal rigid struts are linked in the central node with two set of zero-length link elements. In the present work an improved version of the Furtado model is assumed (Mazza 2019a;Mazza and Donnici 2019), which includes nonlinear behaviour of MIs in the OOP direction and takes into account the reduction in OOP capacity produced by simultaneous or prior IP seismic damage. However, this modelling approach, having struts directly connected to the centroid of beam-columns joints, does not represent accurately the internal actions distribution deriving from the infill-frame interaction (Di Trapani et al 2015;Basha and Kaushik 2018;Gentile et al 2019), so requiring that shear strength of r.c.…”

“…The OOP reduction of strength and stiffness is activated when the displacement corresponding to the maximum IP strength is exceeded and continues up to a fixed drift threshold (i.e. Δ (IP) /h) upper = 0.8%, in the case of weak infills), keeping the OOP backbone unaltered from this point on (Mazza 2019a). These expressions are calibrated on the basis of experimental results available in literature, with reference to weak infill panels (i.e.…”