Abstract
Load carrying capacity of an existing bridge needs to be properly assessed for the safe operation and efficient maintenance. For the evaluation of load carrying capacity considering the current state of a bridge, static and quasi-static loading tests with weight-controlled heavy trucks have been conventionally utilized, where the deflection of structural members loaded by the controlled loading are measured and analyzed. However, full or partial control on traffic during the tests and difficulties in installing displacement transducers may cause not only inconvenience to the traffic but also increase of the logistics cost and time. To overcome these difficulties, an alternative method is proposed using ambient acceleration data excited by ordinary traffic on a bridge without traffic control. Based on the modal properties extracted from the ambient vibration data, the initial finite element (FE) model of the bridge can be updated to represent the current real state of a bridge. Using the updated FE model, the deflection akin to the real value can be easily obtained without measuring the real deflection. Impact factors are obtained from pseudo-deflection obtained by double-integration of acceleration data with removing the linear components on acceleration data. For validation, the proposed method was applied to evaluate the load carrying capacity of a steel plate girder bridge and a pre-stressed concrete bridge. The results show that the proposed method gives a reasonable load carrying capacities without traffic control and with easy installation of sensors.