Damage Assessment of Jacketed RC Columns Using Vibration Tests

Abstract

Damage assessment of reinforced concrete (RC) columns retrofitted by advanced composite jackets was experimentally and analytically studied. The writers built two half-scale bridge columns, wrapped them with the composite jackets, and subjected them to cyclic loading to introduce moderate and severe levels of damage to the columns. Vibration tests using a shaker were performed on these columns before and after jacketing and under undamaged and damaged conditions. The neural network technique was effective in estimating change (representative of damage) in the stiffness based on the measured vibration characteristics. The frequencies and mode shapes of the columns determined from the vibration tests and computed on the basis of the estimated stiffness showed excellent agreement. Pertinent to the purpose of the present study is the success of quantification of the extent and location of stiffness degradation due to different levels of damage. Degradation of the shear stiffness as well as the flexural stiffness in the lap splice region, especially in the 1-in. unwrapped gap portion, of the column was a key parameter to represent the damage.