Abstract
Vibration based structural health monitoring of civil infrastructure is becoming very popular due to advancement in instrumentation and development of more robust and powerful system identification techniques. Damage alters the dynamic characteristics of a structure and this relation is used to identify, locate and assess the severity of damage. Despite of advances in vibration based methods very limited success has been reported for reinforced concrete structures particularly in field applications due to complexity of civil engineering structures, limited measurement points, measurement noise and processing errors. The success of vibration based methods relies on the ability to precisely measure the modal properties. Experimental modal analysis is often carried out to observe the modal parameters among which phase separation methods are very common. Phase resonance methods traditionally used in the field of aerospace and mechanical engineering measures the modal parameters physically rather than mathematically. This paper presents the methodology of phase resonance method with application to a typical reinforced concrete bridge girder reduced to one-fourth scale. Piezoelectric accelerometers at 54 measurement points are used to obtain five modal parameters i.e. natural frequency, mode shapes, damping ratio, generalized mass and stiffness. The comparison shows noticeable variation in extracted modal parameters.