An Improved Capacity Design Procedure Incorporating the Effect of Gap-Opening on Higher Mode Responses in Rocking Wall Structures

Rocking wall structures present a resilient alternative to conventional structures. Although the displacement responses of these structures have been discussed in past works, the force-based responses especially in the context of nonlinearity due to gap-opening behavior need to be explored in detail. In the current research, the effect of gap-opening behavior at predetermined locations in the rocking walls on the seismic force responses has been discussed. For this purpose, five rocking walls of varying heights and against two levels of seismic intensity are designed and analyzed using time history analysis procedure. A modal decomposition technique is used to separate the complex responses to their modal responses to better understand the different factors in play. It is found that the modal properties based on initial stiffness properties are unable to predict the inelastic seismic demands and a new capacity design procedure, based on modified modal properties incorporating the effect of gap-opening, has been proposed. The issues associated with the use of modified modal properties are discussed in detail and a simple, yet effective solution is shown to provide a much better prediction of inelastic seismic responses of these structures.