The John A. Roebling suspension bridge, formerly the Covington-Cincinnati suspension bridge over the Ohio River was completed in 1867 and is still serving the Northern Kentucky community. The objective of this study is to assess the bridge load capacity via the dynamics-based technique. The scope of research includes finite element modeling and modal analysis, field ambient vibration testing, finite element model calibration to field test results, and bridge load-capacity evaluation. It is demonstrated that stress stiffening of cable elements plays an important role in both static and dynamic analyses of the Roebling suspension bridge. Large deflection behavior has been shown to have a limited effect on the member forces and deflections. Dominant vibration modes in the low frequency range are shown to be in the transverse direction. Higher free vibration modes of the bridge are coupled. In the structural evaluation under dead loading, the main cable area is reduced by 10% to 40% to simulate deterioration and corrosion of the cables. It is observed that the safety margin of the main cables remains fair (larger than one) even for the conservative 40% cable area reduction and extreme live loading pattern that equals 40% of uniform dead loading. Similarly, the truss member forces are within the maximum capacity.
The current load limit posting for the Roebling bridge is adequate. In case the load limit will be increased in the future, it is recommended that a detailed study be conducted to evaluate the need to strengthen the top chord truss members in order to increase the loading capacity of the truss.
Digital Object Identifier
Ren, Wei-Xin; Harik, Issam E.; Blandford, George E.; Lenett, Michael; and Baseheart, T. Michael, "Structural Evaluation of the Historic John A. Roebling Suspension Bridge" (2003). Kentucky Transportation Center Research Report. 236.