The Flexural Capacity Degradation Model Of The Concrete Girder Bridge And Maintenance Decision Of Bridges In Rroad Network

In road network, the concrete girder bridge is the main bridge type and most have the issue of bearing capacity degradation, and the degradation affects the normal operation. To make the bridge managers formulating scientific maintenance planning, arranging the limited maintenance funds reasonably, there is a need of studying on flexural capacity degradation model of the concrete girder bridge and maintenance decision of bridges in road network.Firstly, the influence of stress state of concrete to carbonization depth and chloride ion diffusion coefficient are further investigated in this paper, and then the stress influence coefficient of concrete carbonization depth model and chloride ion diffusion coefficient model are corrected respectively. The results show that the concrete stress has a great influence on carbonization depth, and the stress influence coefficient which is proposed in this paper has higher prediction accuracy. The stress influence coefficient has approximately linear function relationship with the tensile stress ratio of concrete, and increases with the increasing of tensile stress ratio. The stress influence coefficient has approximately quadratic function relationship with the compressive stress ratio of concrete, and decreases with the increasing of compressive stress ratio. The concrete stress has a great influence on chloride ion diffusion coefficient, and the stress influence coefficient which is proposed in this paper has higher prediction accuracy. The stress influence coefficient has approximately quadratic function relationship with the stress ratio of concrete, and increases with the increasing of tensile stress ratio, but first decreases and then increases with the increasing of compressive stress ratio of concrete.Secondly, the concrete carbonization depth model and chloride ion diffusion coefficient model in which the stress influence coefficient was modified in this paper are applied to rebar corrosion model, respectively, and then the performance degradation model of concrete and rebar are built. In this paper, the flexural capacity degradation model of the concrete girder bridge is built by five factors which include the cross section area of corroded rebar, the strength of corroded rebar, the strength utilization coefficient of ordinary rebar, the degradation of concrete strength and the degradation of concrete section area. The flexural capacity degradation model which considers a number of factors’ degradation, conforms to the actual degradation rules in a certain extent, and can provide some reference for maintenance and durability design of the concrete girder bridge.Thirdly, under the condition of limited maintenance fund, the maintenance priority analysis of bridges in road network is solved by seven factors and a optimization algorithm, which includes the decline value of the bridge bearing capacity, the importance of the bridge in road network, the average daily traffic volume of the bridge, the bridge inspection and evaluation level, the bridge maintenance cost, the bridge landscape importance, the bridge performance degradation rate and the greedy algorithm. A case study indicates that this priority analysis method is reasonable and can provide reference for bridge managers to build maintenance planning.Finally, in order to reduce the maintenance cost and ensure the bridges which are selected through the priority analysis in the specified service level, the health index is used to measure the health status of bridges and components in this paper. The maintenance method based on the unit weight health index of each component of bridges is proposed, and the maintenance planning of the bridges which are selected through the priority analysis are repaired. Result shows that the maintenance method can reduce maintenance cost and is practical for use.