A Finite Element Study on Seismic Behavior of Various Concrete Column Retrofitting Methods

In recent decades, concrete column retrofitting methods and their seismic behavior under cyclic loading, especially from ductility and energy absorption standpoints, have been extensively focused by researchers. Significant amount of this research has been allocated to confinement of concrete elements in order to advance the ductility and energy absorption capability of the concrete structures facing the forces induced by earthquake. In this study four methods of concrete column retrofitting methods, including FRP plates, steel jackets, and concrete jackets, have been assessed and thoroughly compared with each other in terms of seismic behavior advancement measurements.
To achieve this objective, different retrofitting methods were simulated in ABAQUS FEA software, based on prominent finite element analysis and numerical modeling. The modeling results were verified with equivalent experimental tests which further validates the accuracy of the modeling approach. In addition, the impact of the following variables were studied using sensitivity analysis on the replicated models: Core concrete strength, texture and number of layers of FRP plates, size and thickness of steel plates, and dimensions of concrete jacket, along with diameter and placing of stirrups and bars.
Strength, ductility, and energy absorption capacity of the simulated models were recorded in order to compare efficiency of each retrofitting method. Results have shown that retrofitting through FRP plates leads to increasing ductility. Retrofitting using concrete jackets, despite increasing the energy absorption capability and maximum shear strength, will not result in acceptable ductility. On the under hand steel jackets, along with improving a maximum shear strength and energy absorption ability of the element, shows promising improvement in ductility. Moreover, for the models with the same axial load and lateral load capacity, steel jacketing and concrete jacketing methods have proved to show better ductility, compared to FRP. Plus, steel jacketing resulted in the highest energy absorption capability among all the three methods under the aforementioned condition.