Design of innovative dynamic systems for seismic response mitigation

Abstract

Rocking wall systems consist of shear walls, laterally connected to a building, that are moment-released in their strong plane. Their purpose is to mitigate seismic structural response by constraining a building primarily to a linear fundamental mode. This constraint prevents mid-story failure, and maximizes energy dissipation by activating the maximum number of plastic hinges throughout the structure. This is a useful response mitigation system, but suffers from some difficulties, stemming primarily from the considerable mass of the wall. Those difficulties are notably expensive foundations, and very high inertial forces imparted to the building, with subsequent need for expensive lateral connectors. The purposes of this work are to analyze current implementations of rocking wall systems, present an early reference on their application, present the first systematic methodology for their design, clarify their analysis, and introduce an alternative structural system that avoids their difficulties. A quasi-static analysis model is used for predicting the seismic mitigation performance of rocking walls and rocking columns. The stiffness matrix is generalized for an N-story building equipped with these structural systems. The model presented enables optimization of the design parameters, and consequently improved system effectiveness, analytical tractability, and material usage. The case study is a rocking wall system installed in a building located in Tokyo, Japan. A software package is developed, providing an illustrative implementation of the methods derived.