1 INTRODUCTION Cavity walls are often used in unreinforced masonry (URM) buildings in many countries, such as in Cen- tral and Northern Europe, Australia, New Zealand and China. Double-leaf cavity walls constitute a large portion of the building inventory in the prov- ince of Groningen, a large gas field in the north of the Netherlands, where the number of human- induced earthquakes has recently increased. These buildings are subjected to induced earthquakes up to magnitude of 3.6 until now, with the largest record- ed horizontal PGA of 0.11g. A cavity wall consists of two separate parallel walls (called leaves), with an inner load-bearing leaf and an outer veneer, that has mostly aesthetic and insulating functions (Fig 1). The inner and outer leaves are interconnected by means of metal ties, as described in NEN-EN 845- 1(NEN 2016). The out-of-plane failure is a common mechanism during an earthquake for this typology of walls, which often stems from poor wall-to-wall, wall-to- floor or wall-to-roof connections, which are unable to provide sufficient restraint and boundary condi- tions, as well as from the slender geometry of the two parallel leaves. Lintz & Toubia (2013) proposed a simplified ana- lytical method to determine the amount of load transferred through the ties to the brick veneer and found that placing vertical reinforcement in the outer leaves could allow for an increase of the design strength. An earlier study by Kobesen (Kobesen et al. 2014) defines the wall tie connection strength based on the pulling out of bars from concrete (Bruggeling et al. 1986, Cement en Beton 2011). In the model of Bruggeling (1986), the reinforcement embedded in concrete and subjected to tension is assumed to have the same strains of concrete. Though it uses slightly different stress and strain profile, Braam and La- gendijk (2011) also provides a similar approach. Kobesen (2014) used the same assumption for metal tie embedded in mortar. Figure 1. Cavity wall An experimental campaign was performed at the Delft University of Technology (TU Delft) in 2019 (Arslan et al. 2020) to provide a complete character- ization of the axial behaviour of metal connections in cavity walls by means of a dataset of 202 cou- plets. This work discusses the results presented by Mechanical Modelling of Cavity Wall Metal Ties O. Arslan Department Materials, Mechanics, Management & Design, TU Delft, Delft, The Netherlands Research Centre NoorderRuimte, Groningen, The Netherlands F. Messali & J. G. Rots Department Materials, Mechanics, Management & Design, TU Delft, Delft, The Netherlands E. Smyrou & I. E. Bal Research Centre NoorderRuimte, Hanze University of Applied Sciences, Groningen, The Netherlands ABSTRACT: The seismic assessment of unreinforced masonry (URM) buildings with cavity walls is of high relevance in regions such as in Central and Northern Europe, Australia, New Zealand and China because of the characteristics of the masonry building stock. A cavity wall consists of two separate parallel walls usually connected by metal ties. Cavity walls are particularly vulnerable to earthquakes, as the out-of-plane capacity of each individual leaf is significantly smaller than the one of an equivalent solid wall. This paper presents the results of an experimental campaign conducted by the authors on metal wall tie connections and proposes a mechanical model to predict the cyclic behaviour of these connections. The model has been calibrated by us- ing the experimental results in terms of observed failure modes and force-displacement responses. Results are also presented in statistical format.