Abstract
This study investigates the seismic performance of steel energy dissipation bars, focusing on the impact of bar geometry and external fiber-reinforced polymer (FRP) strengthening. A comprehensive three-dimensional nonlinear finite element model (FEM) was developed using ABAQUS software to simulate the cyclic response of steel bars subjected to cyclic loads. Steel bars with diameters of 16, 22, and 36 mm and lengths of 400, 550, 625, and 800 mm are examined to assess the effects of bar size on strength and energy dissipation capacity. The numerical results show that bar diameter plays a dominant role in determining seismic performance, while the influence of bar length is limited due to the confining cylinder which reduces buckling. Furthermore, the 36 mm diameter bar is externally strengthened using basalt fiber reinforced polymer (BFRP) and carbon fiber reinforced polymer (CFRP) sheets, applied with different fiber orientations: longitudinal (L) and hoop (H). The longitudinal fiber orientation (LLL) demonstrates the most effective enhancement in terms of strength and energy dissipation. In terms of material efficiency, CFRP increases ultimate strength by approximately 9.2%, while BFRP achieves a 7.1% increase. Although CFRP provides a higher contribution to strength, BFRP exhibits superior ductility and sustained energy dissipation capacity, offering improved resilience under severe cyclic deformations. These findings underscore the effectiveness of optimizing bar geometry and FRP strengthening schemes to enhance the seismic performance of post-tensioned steel energy dissipation systems.