An integrated VE damping and FRP strengthening system for performance-based seismic retrofit of RC columns

A damping-enhanced strengthening methodology is proposed to enable a cost-effective retrofitting design of reinforced concrete (RC) columns for multiple performances objectives. This methodology involves the integration of viscoelastic (VE) damping layers and fiber reinforced polymer (FRP) strengthening sheets into one compact retrofitting system. Both analysis and experiment were conducted to develop and validate the proposed methodology and design equation for the retrofitting system. A distributed mass model of a cantilever rectangular column retrofitted with the proposed system was developed according to the Euler-beam theory. Parametric studies were conducted to understand how sensitive the performance of the proposed system is to its design parameters. In the experimental program, VE material properties were characterized under various conditions, the bond behavior between VE layers and FRP sheets as well as the anchorage behavior between FRP sheets and concrete were investigated, and shake table tests were conducted to validate the effectiveness of the proposed system. Test results show that VE properties can be related to excitation frequency and temperature by KASAI equation. The proposed bonding and anchoring mechanisms can effectively transfer damping force from concrete, FRP sheets, VE layers to the foundation of a RC column. The anchorage design equation proposed in this study was verified by test data. Numerical results for 1/5-scale RC columns were compared and agreed well with those from the shake table tests. The proposed retrofit system can increase the damping of small-scale columns by more than 90% and as high as 1500% for the corresponding full-scale columns, depending on their slenderness ratio.