Estimating the flexural strength of corroded reinforced concrete beams based on rectangular compressive stress block

Quantifying the effect of corrosion before structural failure is significant for a cheaper and more efficient repair. In this study, a simple method to estimate the residual flexural strengths of corroded RC beams was proposed based on the equivalent rectangular stress block standardized in the National Structural Code of the Philippines, as adapted from the American Concrete Institute. Model development involved analyzing a total of 93 RC beam specimens available in the literature, which have been damaged by accelerated corrosion. The working formula incorporates a correction factor (Cf), expressed as a function of corrosion degree and beam parameters, to the theoretical moment capacity of damaged beams. Four models of Cf have been proposed: linear, power, and two nonlinear functions. Their validities were confirmed by applying them to a separate set of published data. Computed values showed an average difference of about 20% from experiment, with greater accuracy at flexural strengths below 20 kN center dot m. While the two nonlinear models fit better with the experiment, they overestimated many of the larger flexural strengths. On the other hand, linear and power models mostly give strengths lower than actually measured. This result, however, is preferable from the viewpoint of conservative structural as-sessment. It is recommended to study in future work the applicability of present models to full-scale RC beams that underwent natural corrosion or failed in flexure by concrete crushing.