ERRORS AND IMPROVEMENTS IN RELIABILITY INDEXES OF DESIGN FORMULAE OF CURRENT CHINA CODES FOR DESIGN OF HIGHWAY RC BRIDGES

The current code for design of highway RC bridges in China is based on the Level I reliability method with a few partial safety factors determined on the minimum root-mean-square errors in the reliability index. Using FORM, this paper examines errors between the predicted target and minimum values of reliability indexes corresponding to the different design formulae in the code with errors as large as 2.98, depending on not only the types of the action and material as well as the ratio of load effects, but also the reinforcement ratio, material grades and eccentricity. Thusly, such formulae can not be used for evaluating and strengthening existing bridges. The paper gives new values of the partial safety factors considering the six factors with the regression. With these new values, the errors in the reliability index of the different design formulae are in a range of ±0.1.