SEISMIC PERFORMANCE ASSESSMENT OF ULTRA HIGH-PERFORMANCE CONCRETE FILLED CHAMBERED STEEL TUBE (UHPC-FCST) LONG COLUMNS

Abstract

Columns are critical elements, as their behavior govern the overall seismic response of structures, with additional challenges regard long or slender columns. To overcome these challenges, a novel column’s system of UHPC-FCST is investigated in this research under axial-lateral cyclic loading scenarios, to provide a comprehensive assessment and deeper insight, nonlinear finite element validated model is created using OpenSees. The model incorporated the confinement effect, the restraining effect, materials hysteresis behavior over cyclic loading, local buckling and combined axial-lateral loading. Parametric study included with effect of: Aspect ratio (D/W), Slenderness ratio (KL/r), Width to thickness ratio (W/t), Axial load ratio (n). Particular emphasis is placed on assessing the member throughout investigate and quantify the member’s performance markers of: overstrength factor (Ω), deflection amplification factor (Cd), Secant stiffness and equivalent viscous damping ratio (ξ_eq), at different levels of performance targets. The results showed that column maintains full elastic response at and under life safety performance, chambering enhanced the seismic performance and confirmed favorable seismic performance under high demands. Maximum Ω ranges 1-1.2 due to very high elastic stiffness of the column, Cd and secant stiffness were very sensitive to all parameters, Final ξ_eq ranges as high as 20-50% indicating high energy dissipation, where ξ_eq is less than 10% in the elastic range which compatible with elastic analysis assumptions. Increasing of n is very interacting with W/t, higher n with lower W/t led to better seismic behavior and superior energy dissipation with contrast with higher W/t.