Numerical Investigation on Effect of Confining Reinforcement on Post-Earthquake Fire Behavior of Reinforced Concrete Column

Intermediate tie reinforcement plays a vital role in enhancing the ductility of reinforced concrete columns (RC) by providing effective confinement to the core concrete and restraining the buckling of longitudinal reinforcement. Evaluating the residual load-carrying capacity of RC columns exposed to elevated temperatures following lateral loading. The effects of thermal stresses and deformations on the structural behavior of reinforced concrete columns subjected to fire following earthquake loading are not adequately addressed in conventional design codes. This study numerically investigates the effect of confining reinforcement on the post-earthquake fire behavior of RC columns. Specifically, the effects of confining tie configurations, concrete compressive strength, and transverse reinforcement spacing on column behavior under post-earthquake fire conditions are examined. A finite element model was developed using ANSYS Mechanical APDL 2020 R2 and validated against experimental results reported in the literature. The RC columns were modeled as cantilever members with 300*300 cross-sections. Following validation of the finite element model, a parametric study was conducted involving 19 finite element models. The finite element analysis results show that reinforced concrete column with intermediate confining reinforcement improve the load carrying capacity by 12.48%. Intermediate confining ties increased load-carrying capacity by 4.98% under lateral loading and 11.48% under PEF loading, demonstrating greater effectiveness after fire exposure. Due to the effect of thermal stress, load carrying capacities of the confined and unconfined column by intermediate ties were reduced by 6.38% and 12.5% respectively. Increasing spacing of transverse reinforcement from 100mm to 300mm (i.e. 66.66%) decreases the strength by 4.22%. In other way the strength of concrete increases from 23MPa to 45MPa (i.e. 95.6%), the load carrying capacity of the column was increased by 14.74%.