Influence of 2D and 3D Micro Modelling Approach in Seismic Design of Framed-Masonry Structures with Respect to Hollow Clay Masonry Units

While designing earthquake resistance of framed-masonry structures, EN1998-1 standard states that one should consider seismic actions in- and out-of-the-plane for the given structural elements. The use of micro models is usually limited to the level of a single structural element. Therefore, a 2D or 3D approach can be used. For the purpose of in- plane non-linear response analysis, the use of 2D micro-model is sufficient. On the other hand, for the inclusion of out-of-the-plane response, a 3D model must be used. Besides stated, there are several crucial differences between a 2D and 3D micro modelling approach. In 2D modelling, masonry unit (hollow or solid) is modelled using the vertical properties of the masonry unit, in compliance with EN 772-1 standard. Hence, strength is equal to the maximum force per gross area. Furthermore, the airspace of the hollow masonry units is neglected i.e. they are modelled as solid bricks. The orthotropic properties are captured through contact elements [1]. On the other hand, in 3D modelling, masonry unit is modelled with full geometry and with the material properties same as the material itself. Therefore, strength is equal to the maximum force per net area. In this manner orthotropic properties are assigned directly, which reduces the number of assumptions in a final structure. Consequently, calibration of the 2D models cannot be applied as same as for the 3D models. This work shows an orthotropic 3D micro model of a clay hollow masonry unit, build in ATENA [2] computer program. It is made of two materials as a composite to meet the force and the displacement requirements of the unit in both, the horizontal and the vertical direction. The corresponding material models of the unit and of the contact between the units were calibrated with the test results, which were obtained in compliance with EN 772-1 and EN 1052-3 standards, respectively, as given in [3]. Afterwards, they were implanted and verified through the analysis of a masonry wall in compression build in compliance with EN 1052-1 standard. In conclusion, the tendency of this work is to show how the proper modelling of the wall constituents, mainly masonry units, such as orthotropic clay hollow masonry units, provides adequate response of the more complex model.