Numerical analysis of RC Gerber bridge girder subjected to fatigue loading

Numerous RC bridge girders are on service, various cracks are identified owing to exposure to millions of traffic loads during their service time. The predicted life cycles of these RC members under recurrent loading is difficult to establish. These problems are becoming worrisome since aging bridges are everywhere, hence, their immediate solution is exigent. A case of the collapse of the Gerber bridge girder (De la Concorde) in Canada has been identified and numerically analyzed. Three-dimensional failure mode of the girder subjected to high cyclic loading has been predicted under moving wheel, and fixed-point pulsating at the centre and a span away from the centre. A step-wise load application of 5 million cycles of 5 time-steps, corresponding to 0.003 seconds. Constitutive model of smear cracks in concrete using the direct path-integral approach, and mesh model of quadrilateral elements of eight nodes that captures the shear, compression and tension scenarios was adopted. The random application of cyclic loads, material properties and geometry are the contributing factors to the failure of the Gerber girder as shown by the analysis. Critical areas/sections that required attention have been identified.