Physical and mechanical metallurgy of premature failure of tie rods of a cable-stayed bridge

Tie rods of a newly constructed cable-stayed bridge failed after being in service only for six months. Failure occurred during winter months. Detailed metallographic analyses of the microstructure and fracture surfaces, supplemented by oblique section metallography, have been carried out. Results indicate that the final failure mechanism was cleavage due to lack of low temperature toughness of the steel used. Fatigue crack propagation due to cyclic and uneven loading was also an important contributing factor. The use of higher toughness steels with intrinsic weathering resistance has been suggested as a possible remedial measure.