A monumental bridge with a problem caused by oversights in design

Abstract

In January 2004, one of the lower hanger plates of the Bosporus Bridge in Istanbul, Turkey, fractured. Emergency repairs were performed on some of the plates and a bridge evaluation project was initiated to understand the cause of the problem and to devise appropriate solutions. This paper summarizes the evaluation process and the results. The scope included short- and long-term hanger force and plate strain measurements, finite element analysis, non-destructive testing (NDT), probabilistic analysis, and remaining service-life estimation. The investigation showed unusual behaviour of the bridge superstructure that is attributed to the inclined configuration of the hanger cables introducing additional stiffness and attracting additional forces from a variety of sources. The evaluation has shown that many of the hanger plates are at the critical stage of their service life. This paper describes an example of oversights in design that has left a monumental bridge in a critical condition 30 years after its construction.