Date of Award
Master of Science (MS)
M. Z. Naser
Recently, there has been increased interest in using buckling-restrained braces (BRBs) in pinned precast concrete frames located in seismic zones. BRB frames (BRBFs) are a relatively new, but well-understood lateral force resisting system for steel structures. A codified method of design for precast BRBFs cannot be created due to a lack of experimental studies on this system. To act as a first step in the codification process, the objectives of this thesis are to complete an extensive review of potential brace-to-frame connection designs for precast BRBFs and to experimentally test a connection design through representative seismic loads. To complete the first objective many potential connection designs were examined, including some that had the advantage of eliminating gravity load transfer from the precast frame into the connection or brace. Some of these connections were candidates for testing, but constructability issues, undesirable bolt loading states, an incompatibility with a wide range of bay sizes, and other factors caused these connections not to be chosen for test. A traditional gusset plate connection using the Uniform Force Method (UFM) for force distribution was selected for the experimental program as it is widely used for BRB connections to steel frames. A quasi-static cyclic test was performed on a scaled, partial precast frame to determine the validity of the connection interface forces predicted by the UFM as compared to the interface forces observed in testing. Additional conclusions about the behavior of the system were inferred using a simplistic finite element model correlated to the experimental results. Experimental results implied that the UFM alone is not accurate in predicting gusset plate interface forces for this system. The test results indicated there is likely some change in this distribution due to frame action. In addition, a deviation from the pinned force distribution among precast members that varied with frame displacement implied that there is some change in column base fixity as the frame undergoes larger horizontal displacements. The simplistic finite element model tuned column base stiffness and showed an increase in stiffness as a potential cause for this deviation. This thesis concludes by outlining two possible approaches to continue research towards codification of precast BRBFs based on the results of this research.
Kessler, Hannah Dillingham, "Initial Investigation of Connection Behavior for Buckling-Restrained Braces (BRBs) in Precast Concrete Frames" (2021). All Theses. 3615.