Out-of-Plane Dynamics of Hollow Clay-Brick Infill Walls: Numerical Modelling and Experimental Test

Many past seismic events have shown the high vulnerability of infill walls to in-plane (IP) and Out-of-Plane (OoP) actions. While the in-plane behavior has been more extensively investigated, the OoP needs further development from both modelling and experimental points of view. In this framework, this study focuses on infill walls made of cement-lime mortar and hollow clay-ceramic bricks, cast in place with horizontal holes, and typically have a void content of 65% or higher. One parameter used to evaluate the seismic demand of a non-structural element, according to the codes, is its natural period. Simplified formulas have been proposed for computing it in infills, accounting for relevant aspects such as geometry, mortar type, and boundary restraints. In the case of hollow brick infills with horizontal holes, different bending stiffness values characterize horizontal and vertical directions. Therefore, in this paper, a continuous model is chosen to represent the OoP dynamics of this type of infill. Starting from the existing plate solutions, an orthotropic model is defined to represent the dynamics of the homogenized wall, and nondimensional solutions are derived by the Galerkin approach. For validation, a laboratory test was done on a 14 cm infill wall, using ambient vibrations and impulsive excitations exerted by a hammer. MEMS accelerometers were used, and dynamic properties were evaluated by the Frequency Domain Decomposition (FDD) method.