Phenomenological hysteretic model for corroded RC columns

A phenomenological hysteretic model is developed for corroded RC columns in this study. To this end, the test data of 77 corroded rectangular RC columns and 26 uncorroded ones under repeated cyclic loads are collected to establish a database. A polygonal hysteretic model that can well incorporate the degradation of stiffness and strength is adopted to describe the hysteretic behavior of corroded columns. The hysteretic model parameters related to monotonic backbone (i.e., yield moment M-y, yield rotation theta(y), pre-capping rotation theta(p), post-capping rotation theta(pc), the ratio of capping moment to yield moment k) and cyclic deterioration (i.e., cyclic deterioration parameter lambda) are identified for each of the test specimens in the database after a careful calculation with the experimental data. The backbone parameters identified for the corroded columns are compared to those for the uncorroded columns to quantify the corrosion-induced deterioration coefficients (CIDCs). Multivariate-linear-type empirical relationships are then developed to relate each of the CIDCs to the corrosion rate and critical structural design variables using stepwise regression analysis. A multilinear empirical relationship is also proposed for the cyclic deterioration parameter. The developed hysteretic model together with the predictive equations for the model parameters are proved of high accuracy through simulating the intra-database tests considering varying corrosion levels. They are further applied to the corroded columns beyond the database, those without data on uncorroded counterparts provided in particular, also indicating a desirable accuracy.