Reliability Analysis Of Existing RC Bridges

Reliability assessment of existing RC bridge is an urgent role to be reserved in our country. The structural characteristic of RC bridge is that the resisting force is deteriorating in life service of bridge,but most of reliability researches don't consider the attenuation of resisting force until recent. In this paper,based on resisting force model and load model,the limit state equations of RC bridge are established,thus the time-dependent relationship of RC bridge reliability is analyzed.Firstly,each single factor(concrete carbonation,steel bar corrosion materials strength) related the resisting forces of RC bridges is considered in this paper. Then a resisting force model for multiple factors is created based on two types of steel bar corrosion:general and localized corrosion models.Load is a main factor to influence bridge. The main loads of RC bridge are deal load vehicle load which are random variables. Based on survey data from some researches,dead load model and vehicle load model are presented in this paper. It is quite evidence that dead load model is Gaussian distribution,and vehicle load is non-gaussian distribution,which operates general traffic and rush hour traffic states. At last distribution functions of load modes in life service are presented.Based on the resisting force model and load model,the limit state equations of RC bridge are formulated. According to the resisting force is time-dependent and vehicle load is the non-gaussian distribution,JC method is applied to calculate the time-dependent reliability index of RC bridge. Finally an engineering example is analyzed. Reliability index is determined considering two types of corrosion models and two types of vehicle models. The influences of some parameters,such as dead load live load,corrosion speed,diameter of steel bar,are analyzed.