Full-scale dynamic testing of non-ductile reinforced concrete frame retrofitted with innovative SMA bracing device (Frame #4a)

This study presents full-scale shaker-excited dynamic tests of 2-story and 2-bay non-ductile reinforced concrete frame retrofitted with a shape memory alloy (SMA) bracing device. The RC frame is nominally identical to Frame #1 (Experiment #4 in this NEES Project). The aim of this study is to evaluate seismic retrofit effectiveness of this innovative bracing device for a non-ductile RC frame. The braces were only installed on the first story.

This study was denominated Experiment 4a. After this test series, a decision was made to stiffen the 2nd story with steel cables in order to drive more force into the braces. Once the 2nd story was stiffened, all subsequent tests were denominated Experiment 4b. Data from that test series is included as a separate experiment on NEEShub. The key findings of this investigation were:
1) The SMA braces effectively suppressed the story vibrations and recentered the frame upon removal of the external lateral loads (shaker input loads).
2) SMA wires can be applied into braces without breaking as long as the design appropriately limits the peak SMA strain demand to the permissible strain range.
3) The brace end connection linked the brace to steel members anchored to the RC frame. It was designed by applying AISC seismic provisions and ACI ‘anchoring to concrete’ specifications, as appropriate. The connection successfully transferred forces without damage to the steel or concrete members.