Numerical Investigation of R/C Columns Before and After FRP Strengthening Under Seismic Type Loadings Utilizing a Novel Anchoring System

Abstract

The behavior of R/C columns before and after strengthening using FRP sheets is discussed here. The study focuses on the bending failure of columns. In particular, three numerical models of RC columns were developed representing a structural subassembly of a RC frame structure. One unstrengthened column and two strengthened with 1 FRP sheet and different bond strength. The numerical models employed all the mechanical properties of the materials explicitly, representing the concrete volume as solid finite elements, the steel reinforcement as wire elements and the FRP sheets as shell elements together with nonlinear interfaces capable to simulate the debonding mode of failure. The seismic type loads are applied as a monotonic horizontal load at the floor's slab level. Furthermore, as the structural upgrade is limited due to the delamination of the strengthening coating, a mechanical anchoring system is investigated and two more models are developed, with the FRP layers ideally anchored. The numerical predictions exhibited a significant increase of bearing capacity, over 50%, when FRP sheets are mechanically anchored. Finally, the novel anchoring system is fully simulated with all its details.