The Concept of an Elastic Rocking Steel Shear Wall

Abstract

Conventional steel panel shear walls (SPSWs) are now well-established ductile seismic-resisting systems. SPSWs comprise thin steel plates (web plates) connected to beams (horizontal boundary elements) and columns (vertical boundary elements) and which resist lateral shear forces through a combination of shear resistance from the plates and flexural resistance from boundary element frame action. The shear action in web plate is resolved into diagonal tension and compression principal stresses and after the compression diagonal buckles, the web plate behaves effectively as tension cross bracing. The ductile action is achieved through tensile yielding of the thin web plates with the boundary elements designed and detailed to remain essentially elastic. When the web plate yields, there is no mechanism in the system to force the structure to return to its original position. This paper introduces the development of a rocking SPSW which combines an elastic tension field action to resist the shear force and a device to dissipate energy and force self-centering of the SPSW. The intention of this innovative new system is to keep the SPSW elastic during the rocking and to provide self-centering after an earthquake. The tension fields distribute the shear forces to the end posts of the topmost and bottommost beams. The devices installed at the bottom of the columns provide the energy dissipation and the ability to self-center. In addition, the devices can be preloaded, so that the SPSW does not commence rocking unless the lateral force exceeds the preloaded value. A rocking base point at the bottom middle of the wall is designed to reduce vertical movements at the wall edges during rocking and to transfer the base shear into the foundation system. Besides introducing the concept of the advanced SPSW, the preliminary design approach and numerical model are also presented.