1 INTRODUCTION Inspections of existing structures are a fundamental aspect of every structural management system. In fact, structural deterioration depends on such a wide range of factors, that direct observation must be con- sidered the prime source of accurate and reliable in- formation on the structure. Inspections are not, however, free of errors and uncertainty (Phares et al. 2004). In fact, the result of an inspection depends on several factors such as the experience of the inspector, the deterioration mecha- nisms present, location of the bridge, and means available for the inspection. Moreover, the results of inspections alone do not allow a medium or long term planning, and any decisions based on the results of inspections alone will result in application of maintenance to very deteriorated structures, resulting in a very high life-cycle maintenance costs (Neves, Frangopol and Cruz 2006; Neves, Frangopol and Petcherdchoo 2006). For these reasons, it is fundamental to integrate the results of inspection with a prediction model for the deterioration of existing civil infrastructure. In this manner, more accurate predictions of future de- terioration will be possible, and more efficient deci- sions can be made. In this paper, the deterioration of existing struc- tures is analyzed considering the model developed by the authors (Neves and Frangopol 2005). In this model, the performance of structures is defined in terms of lifetime probabilistic condition, safety, and cost profiles. The main advantages of this model are the ability to consider the entire performance history of the structure, including deterioration and effects of maintenance actions as well as the ability to com- bine common performance indicators, namely the condition index, with more consistent indicators, such as the safety index. The model proposed by the authors (Neves and Frangopol 2005) does not include any information resulting from inspections or tests in the analysis, as it bases the evolution over time of performance on expert judgment alone. In this paper, a model for combining expert judgment in the form of the model proposed by Ne- ves and Frangopol (2005) with information from in- spections is proposed. This new approach is based on the use of Bayesian updating combined with simulation for improving expert judgment. The re- sults obtained in the examples analyzed show the significant impact on performance prediction of the inclusion of information obtained from inspections. Life-cycle performance of structures: combining expert judgment and results of inspection L.C. Neves New University of Lisbon, Caparica, Portugal D.M. Frangopol Lehigh University, Bethlehem, Pennsylvania, USA ABSTRACT: Current bridge management systems base decisions on the results of visual inspections. These systems consider visual inspection results as accurate and disregard any further information available. In the present study, the result of each inspection is considered as a random variable, dependent of a wide range of factors, that can be integrated with other sources of information, including expert judgment and results of other inspections. The combination of different sources of information results in reliable posterior information and allows more accurate predictions of future deterioration. In the present paper, performance of an existing structure is obtained in terms of the condition index, which describes the effects of deterioration as can be seen by an inspector, and the safety index, which measures the safety margin of the structure. The reduction in uncertainty associated with periodical inspections is considered through updating of performance profiles. The updating of the condition index is direct, as new information on this parameter is collected by the inspec- tor. In terms of safety, however, only indirect information is collected and the uncertainty reduction associ- ated with an inspection is significantly lower. Several realistic examples show the impact of inspections on the predicted life-cycle performance of structures.