Vibration-based method to detect prestress loss in beam-type bridges

Abstract

The loss of the prestress force is an uncertain parameter that may jeopardize the safety of PSC bridges. The prestress force is used to control crack formation in concrete, to reduce deflections, and to add strength to prestressed members; therefore, a substantial prestress-loss can lead to severe problems in the serviceability and safety of the PSC structures. A vibration-based method to detect prestress-loss in beam-type PSC bridges by monitoring changes in a few natural frequencies is presented. A SID (system identification) model is formulated to estimate changes in natural frequencies of the PSC bridges under various prestress forces. Also, an inverse-solution algorithm is proposed to identify the prestress-loss in the PSC bridges by using the changes in natural frequencies. The feasibility of the approach is evaluated using PSC beams for which a few natural frequencies are available for a set of prestress-loss cases.