Seismic performance of underground structures improved by using PET FRP retrofitting central columns

The seismic failure mechanism of underground structures presents that the insufficient lateral deformation capacity of central columns will result in the collapse of the overall structure. Therefore, this study proposed applying Polyethylene Terephthalate Fiber-reinforced Polymer (PET FRP) to enhance the lateral deformation capacity of the central columns of underground structures and then improve the seismic capacity of the overall structures. The numerical models of PET FRP retrofitting reinforced concrete (RC) columns subjected to high axial loads and increasing cyclic deformations were verified by experimental results. With the calibrated models, the inter-story deformation capacity of the underground structures with and without PET FRP retrofitting was contrastively analyzed, and the seismic response of the two underground structures subjected to both horizontal and vertical ground motions was simulated and discussed. It was found that the PET FRP retrofitting structure experienced smaller earthquake threats due to the larger lateral deformation capacity. Furthermore, the repairability of the PET FRP retrofitting underground structures after earthquakes was also investigated. Numerical results presented that applying PET FRP retrofitting central columns of underground structures could improve the seismic performance of overall underground structures.