RISK ASSESSMENT OF THE DESIGN OF REINFORCED CONCRETE BRIDGES

Abstract

The process of building a bridge consists of planning, design, and construction. In each of these stages uncertainties may occur, which can be caused by human or natural effects. Human causes of uncertainties include intentional or unintentional deviation from optimal realization, the use of inappropriate materials, unverified construction methods and changes to the design. Natural effects are often unpredictable, thus, the need for reliability assessment. This research focused on the determination of the level of risk associated with reinforced concrete bridge elements when all design variables are random in nature. The First-Order Reliability Method (FORM) was employed in the computation of the implied levels of risk at the ultimate limit state. A representative reinforced concrete bridge was selected and the load effects on the various components of the bridge were estimated using the limit state equation of each structural element. The results show that reliability index of all elements are as low as 0.5, except for the pier having reliability index of 3.8 within the computed design loads. It was also shown that the reliability index of any element degenerated with increasing accidental loading. In practice, the implication of this trend is a catastrophic violation of the limit state. However, the columns, if properly constructed, would have the best performance while the foundation design has been shown to be grossly inadequate. The findings in this study have attested to the necessity of reliability check on proposed design of any reinforced concrete structure.