Damage evaluation for RC bridge piers using vibration measurement

In order to exhibit the structural integrity and foundation flexibility of a bridge pier through its vibration characteristics, a simplified 2-DOF pier model was proposed, in which the column flexural damage as well as the foundation stiffness reduction of the pier is simulated by a rotational spring. The rotation impedance can be estimated according to the natural frequency of the pier to show the damage level of the pier. A vulnerability index for viaduct based on the microtremors proposed by Nakamura was also introduced for the damage evaluation of bridge piers. In addition, an average spectrum analysis scheme for long-term vibration measurement was utilized to eliminate the dispersion in the identification of vibration characteristics of structures. Experimental investigation was made through ambient vibration measurements on scaled bridge pier specimens of a series of lateral loading tests which were to study the rocking response of the spread foundation. The measurements were conducted prior and posterior to those loading tests, in both fixed and flexible base conditions. Accordingly, the methods utilized were verified to give a reasonable assessment of the damage level of the bridges piers.