Nominal moment capacity of partially deteriorated AISC W-section beams

Abstract The moment capacity of partially deteriorated beams is usually estimated based on the deteriorated section properties regardless of the deterioration length along the beam, which in many cases underestimates the overall capacity of the beam. Structural deterioration in steel bridge girders is usually caused by ageing, corrosion, fatigue, and higher load demands. Area losses in the steel beam cross-section due to this deterioration result in an overall reduction in the beam's flexural capacity. This loss in the flexural capacity varies significantly for different AISC W-sections. In this paper, a new dimensionless section property named WSSR (W-Section Sensitivity Ratio) is proposed and used as a relative indicator of the sensitivity of the section to the loss of its moment of inertia due to the loss of part of its flange area. A new term is introduced for partially deteriorated beams named “equivalent yield moment”. Consequently, a parametric study was conducted using a numerical finite element model calibrated using experimental test results in order to correlate the WSSR to the loss in the nominal flexural capacity. Moreover, a new design (code independent) nominal capacity chart is generated to accurately determine the “equivalent yield moment” and corresponding deflection of the partially deteriorated steel girders using the deterioration in sectional inertia and the deterioration length along the beam.