Experimental Investigation of a Concentrically Braced Frame with Replaceable Brace Modules

Abstract

When designing and building special concentrically braced frames (SCBFs), the common practice is to join the brace to the frame members using a gusset plate that is sized such that the brace buckles in the out-of-plane direction. This detailing requires time-consuming field welding, and out-of-plane brace buckling can damage the surrounding partitions and cladding. Moreover, the gusset plate will experience damage when the brace buckles, requiring the plate to be cut out and replaced after the earthquake. To improve this, an alternative connection was recently proposed in which all damage is intended to be confined to a replaceable brace module (RBM) so as to minimize the time of postearthquake repairs. Moreover, to improve constructability and repairability, shop-welded and field-bolted connections are used and detailed such that the brace will buckle in the in-plane direction. Previous testing validated this concept only for individual RBMs. To assess the interaction of all the braced frame components, this paper presents the results of an experimental study of 70%-scale one-story one-bay concentrically braced frame systems with RBMs. Three specimens were tested to examine the response with three different beam–column connection details. For each specimen, a sequence of tests was performed, the first with initial RBMs and the second with replaced RBMs. All tested systems sustained multiple inelastic cycles with an interstory drift range of 3.6%–4.0% prior to brace fracture. The RBMs were replaced easily and provided essentially the same level of performance as the original RBMs. Postfracture strength of as much as the nominal design shear resistance was also observed due to frame action, even without gusset plates at the beam–column intersections.