Study On Optimum Inspection And Maintenance Strategy For Bridges Based On Gamma Process

Abstract:Currently, the massive and extensive bridge construction is in progress in China. The performance of these constructed infrastructures inevitably deteriorates with service time while the loads increase at the same time, both of which lead to an increasing probability of failure. In order to maintain the serviceability of the bridge, inspection, maintenance and repair should be carried out during the operation. However, comparing with the almost unlimited amount of infrastructures, the resources and funds are always limited. Thus, how to balance the benefit and the cost is widely concerned by owners and administrators. In this paper, to comply with the uncertainties involved in the deterioration, the Gamma process is employed to simulate the initiation and propagation of deterioration process caused by corrosion in steel of reinforced concrete bridge and fatigue crack length in steel bridge. Further, considering the uncertainties of inspection and the effects of different types of maintenance, a probabilistic optimum model aiming at maximizing the service life and minimizing the whole life cost is established to get the Pareto solutions of inspection and maintenance strategies, which can offer advice to these owners and administrators.The main work and conclusions are listed below.1. Basic theory of Gamma process and the calculating process of simulating the deterioration process are presented firstly. Then the service lifetime of structures influenced by corresponding factors is predicted according to the time when the value reaches the predetermined threshold. A decision tree model is further set to calculate the expected service lifetime under different strategies of inspection and maintenance.2. To formulate the whole life cost comprising the cost of inspection, the cost of maintenance and the cost of failure. The decision tree model is used to estimate the whole life cost under different strategies of inspection and maintenance. Finally, a multi-objective optimization model is set up to find the optimum inspection and maintenance strategies.3. The30m span reinforced concrete (RC) girders of Guangxi Tieshan Port Bridge are taken as an example. The localized corrosion in hollow slab girder caused by chloride penetration is used to indicate the performance deterioration. Setting the inspection time, inspection method and damage criteria for maintenance as optimization variables, the Pareto solutions are finally obtained. Results show that, Pareto solutions can offer advice on the strategy scheduling for corrosion in RC bridges. Owners or administrators can choose the most suitable strategy according to their own budgets and demands.4. Another case study aiming at optimizing the inspection time and the type of maintenance for fatigue crack in steel bridge, which sets the crack length as the indicator of deterioration is calculated. The Pareto solutions show that, the proposed optimum model can also be applied to the member of steel bridge and the Pareto solutions can provide a variety of maintenance strategies.