Damage assessment of jacketed RC columns using vibration tests

Damage assessment of reinforced concrete (RC) columns retrofitted by advanc ed composite jackets was experimentally and analytically studied. The write rs built two half-scale bridge columns, wrapped them with the composite jac kets, and subjected them to cyclic loading to introduce moderate and severe levels of damage to the columns. Vibration tests using a shaker were perfo rmed on these columns before and after jacketing and under undamaged and da maged conditions. The neural network technique was effective in estimating change (representative of damage) in the stiffness based on the measured vi bration characteristics. The frequencies and mode shapes of the columns det ermined from the vibration tests and computed on the basis of the estimated stiffness showed excellent agreement. Pertinent to the purpose of the pres ent study is the success of quantification of the extent and location of st iffness degradation due to different levels of damage. Degradation of the s hear stiffness as well as the flexural stiffness in the lap splice region, especially in the I-in. unwrapped gap portion, of the column was a key para meter to represent the damage.