Future life evaluation of existing steel bridges

Abstract

Bridges play a major role in road networks. Continuous health monitoring and proper maintenance of bridges is required to obtain the maximum service from them. Life evaluation of bridges is part of the health monitoring work, which is usually done when bridges get to the end of their design lives under designed service loading or after accidental situations such as overloading or partial collapse of bridges due to floods, landslide, cyclones, earthquakes, bomb blasts, traffic accidents or after unexpected traffic overloading. Health monitoring and assessing structural soundness of existing bridges is important for making economical decisions on repairing, retrofitting or replacing them. Knowing the future life of existing bridges is important for planning new bridges before the old bridges collapse. This paper describes various methods used for fatigue life evaluation of existing steel bridges, the use of stress-life & strain-life curves and finite element models. It explains the four types of fatigue which occur in structural elements due to different magnitudes of cyclic stresses. It also describes the importance of selecting the appropriate life evaluation method. A case study is given as an example in which some of these techniques were used.