Abstract

Existing spillway piers constructed more than 60 years ago in Japan are usually reinforced with round rebars and have very low rebar ratios; consequently, their seismic response may be strongly influenced by post-cracking bond–slip. However, the applicability of nonlinear analytical models to such piers has not yet been systematically clarified. In this study, practical modeling strategies for existing spillway piers were investigated by performing Incremental Dynamic Analysis (IDA) using both a beam model based on nonlinear moment–curvature (M-φ) relationships and a 3D finite element analysis that explicitly accounts for bond–slip between concrete and rebar. An actual spillway pier was analyzed at multiple seismic intensity levels, and the effects of bar diameter, rebar ratio, and bond condition were examined via 3D finite element analysis. The results showed that the beam model is useful for global screening but may misclassify the damage mode because it cannot explicitly represent bond–slip. By contrast, the 3D finite element analysis reproduced flexure-dominant damage patterns and quantified the influence of bond–slip on maximum displacement, residual displacement, rebar strain, tensile damage distribution, and compression damage distribution. These differences became more pronounced under stronger ground motions and for larger bar diameters and lower rebar ratios. The findings support a staged strategy for seismic performance evaluation that combines beam models for global screening with 3D finite element analysis for detailed member-level assessment.

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