ABSTRACT
ABSTRACT: Fatigue at steel bridge structures is one of the major problems that often times do not reveal itself until later stages of damage. Design of fatigue prone members or connections is vital especially for non-redundant fracture critical elements. Cyclic traffic and/or wind loads on bridges can further aggravate stress variations at connections. Bridge members or connections that reach their fatigue life or get damaged due to other reasons may become difficult to replace or rehabilitate especially for suspension bridges. This paper addresses cable hanger plate fatigue problem of a suspension bridge, Bosporus-Istanbul, and also discusses alternatives for hanger plate replacement procedure that will not result in disruption of the traffic. Transfer of cable tensile load to the bridge through alternative paths is necessary for replacing the cable connection plate. Four alternatives are generated for load transfer: a) bypass by supplementary ‘V’ cables connected to the original cable, b) in-plane cable transfer, c) direct connection to the main suspension cable, and d) inverted ‘U’ shape bypass frame for improved stability. Cable strain measurements that will be taken during the load transfer process would allow measurement of axial load existing on cables. The strain based measurement of cable force can be compared against vibration based measurement to calibrate for the unknowns such as i) cable boundary conditions, ii) cable bending rigidity, and iii) cable inclination. Furthermore, measurement of cable strains during cable plate replacement enables comparison of axial load on the cable prior to and after the connection plate replacement. Permanent instrumentation of cables would allow health monitoring of cables and determination of traffic-temperature loading versus cable force relations.
