Design strategy for the rocking stability of horizontally restrained masonry walls

This paper investigates the pure rocking of a rigid block with horizontal restraints. The model simulates the behavior of a masonry wall connected to transverse walls and/or steel tie-rods, very frequently adopted as safety measures against seismic actions. From the system rotational stiffness, found for a Winkler-type model and for a single restraint, the resonance conditions of the horizontally restrained blocks are defined. The role of the horizontal restraint can be unilat-eral (acting only one direction of rotation) and/or bilateral (restraint with similar stiffness in both directions). Real earthquakes or Ricker’s wavelets, representing near-fault ground mo-tions, are assumed as input parameters. It is found that in the bilateral case the response is more predictable, as response spectra are monotonic curves whit a reduction of normalized rotation obtained for higher values of restraint stiffness. Moreover, the effect of horizontal re-straints is beneficial for the range of frequency parameters valid for typical masonry walls. These considerations allow to define a design strategy to ensure the rocking stability of re-strained masonry walls, through a self-centered rocking behavior.