Dynamic Testing of Structures with Ductile Anchorages: A Comparison of Superstructure and Base Connection Plasticity

摘要

Current design philosophy is predicated on the assumption of significant inelastic behavior of the superstructure. Examples include elongation of bracing elements or plastic rotation of beam-column elements in a moment frame. However, designing for such behavior may necessitate repair or replacement of these elements following even a moderate earthquake. Designing for plasticity at strategically designed concrete anchorages is an appealing alternative, achieving the same basic objectives as superstructure plasticity while concentrating damage in ductile concrete anchors. Such anchors can be relatively cheap, accessible, and easy to replace. This paper presents recent shake-table testing of four miniature steel buildings designed to elicit behaviors ranging from superstructure-dominated to base-connection dominated. In these experiments, the base ductility is invoked via the concrete anchorage. The measured local response of superstructure hinge elements and base connection elements, as well as their contributions to overall structural behavior, are compared for the various systems. Improvements to overall structural behavior, including up to 25% reduction in total base shear, are observed with the proposed base-dominated system. The feasibility of replacing damaged anchors after the seismic event is also demonstrated.