Multiscale Analysis on Seismic Response of Underground RC Structure with Uniformly Corroded Sidewall: Effect of Strengthening Using Various Methods

This study numerically investigates the seismic response of corroded underground reinforced concrete (RC) culverts strengthened using various methods. A multiscale model for corrosion and seismic analysis, accounting for strengthening effects, was first validated through quasi-static cyclic analysis of corroded RC columns with and without strengthening. In addition, an actual 40-year-old underground RC culvert was chosen to conduct nonlinear dynamic analysis, where it was assumed that uniform corrosion occurred in the longitudinal reinforcing bars in the sidewall, and that various strengthening methods were applied to restore the degraded seismic resistance performance owing to corrosion. The strengthening methods considered included replacing the sidewalls' interior damaged concrete with new concrete materials and attaching carbon fiber-reinforced polymer (CFRP) laminates or precast concrete (PC) panels to the sidewall. In the nonlinear dynamic analysis, the earthquake was applied to the RC culverts in the direction perpendicular to the sidewalls. Under this specific loading orientation, the mechanical interaction between adjacent structural units was assumed to be negligible. Based on the numerical parametric study results, the strengthening effect of each method was discussed comprehensively. The analysis revealed that as the corrosion degree (CD) increased, shear crack damage in the sidewall became more concentrated, and among the strengthening methods, attaching PC panels proved to be the most effective for restoring the seismic performance of corroded RC culverts.