The FAI 24 Bridge spans the Ohio River between Massac County, Illinois and McCracken County, Kentucky near Paducah, Kentucky. The total structure length is approximately 5,560 feet and features two tied arch spans of 630 feet and 730 feet.

Throughout the service life of the structure, fatigue cracks developed in numerous details throughout the steelwork of the tied arch structures. The tied arches were unsuccessfully rehabilitated several times prior to Modjeski and Masters’ involvement with the structure. However, fatigue cracks were still propagating at many of the details in both tied arches.

Modjeski and Masters was contracted by the Department to investigate the cause of the cracking and come up with a solution to the problem. The engineering services provided to the Department can be grouped into two phases:

Personnel from the Firm thoroughly inspected both tied arch structures. The field investigation involved the use of strain gages and acceleration monitoring equipment. From these investigations, retrofit recommendations were provided.

Retrofit concepts and procedures were developed using finite element modeling. Contract drawings and specifications were prepared and field consultation was provided during construction.