Design strategy for the rocking stability of horizontally restrained masonry walls

Abstract

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 unilateral (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 motions, 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 restraints 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 restrained masonry walls, through a self-centered rocking behavior.