Finite Element Analysis of Seismic Performance of Concrete Columns Confined by Bidirectional Spiral Stirrups

To address the construction difficulties caused by excessively small stirrup spacing in reinforced concrete columns with high seismic demands， as well as the issue of stirrup “unlocking”， this study proposed a concrete column confined by bidirectional spiral stirrups and conducted a finite element analysis on its seismic performance. Drawing upon existing experimental research， numerical simulations were performed using ABAQUS software， and the model’s validity was verified. Based on the validated model， the effects of various parameters， including the axial compression ratio， concrete strength， stirrup spacing， stirrup diameter， and stirrup configuration， on the seismic performance were systematically analyzed. Furthermore， the confinement effect of thin-walled circular steel tubular columns with an equivalent volumetric steel ratio was investigated for comparison. The results indicated that the ductility of the concrete columns decreased as the axial compression ratio increased. In contrast， the bearing capacity initially increased with increasing axial compression ratio but began to decline after the ratio exceeded 0.5. Higher concrete strength and larger stirrup spacing led to reduced ductility. While increased concrete strength enhanced the bearing capacity， larger stirrup spacing reduced it. Increasing the stirrup diameter improved both ductility and bearing capacity. Under identical stirrup spacing， the concrete columns with bidirectional spiral stirrups exhibited a higher bearing capacity than those with unidirectional spiral stirrups. For an equivalent volumetric stirrup ratio， the bidirectionally confined columns demonstrated better ductility than their unidirectional counterparts， without a significant compromise in bearing capacity. At an equivalent volumetric stirrup ratio， the concrete columns confined by bidirectional spiral stirrups demonstrated superior ductility and offered enhanced seismic performance compared to the thin-walled circular steel tubular columns.