Effect of Target Reliability Level on Partial Factors for Existing Steel Railway Bridges

Many existing steel railway bridges, often recognized and protected for their heritage value, are exposed to degradation and increasing traffic loads and their reliability needs to be assessed. The key question is whether a particular bridge can be preserved, or needs to be strengthened or replaced. The main aspect in decision-making is specification of the target reliability. Development and wider use of the adjusted partial factor method seem to be reasonable to find the balance between demands on the input information, computational complexity, and improvements in reliability assessment. Adjusted partial factors are based on the relevant statistical parameters for basic variables and a selected target reliability index. In this contribution, the effect of the target reliability on updated partial factors are demonstrated. The case study illustrates that the target reliability levels recommended in various documents for new and existing structures are inconsistent in terms of the values and criteria according to which these values are to be selected. Consequently, the values of the partial factors for assessment may be significantly dissimilar.