Partial interaction stresses in continuous composite beams under serviceability loads

Abstract

The number of fatigue assessments of composite bridges is growing rapidly worldwide due to increasing allowable load limits and because many of the bridges are reaching the end of their anticipated design life. Special attention is usually given to predicting the residual endurance or strength of the shear connection because it cannot be visually inspected. However, the increased stresses in the steel and concrete components due to partial interaction must also be considered in a fatigue assessment. Based on linear elastic partial interaction theory, this paper develops a simplified procedure to predict the partial interaction curvature in continuous composite beams. When used in conjunction with focal points, the partial interaction flexural stresses in the steel and concrete components can be determined and used to more accurately predict the residual strength or endurance of the composite section. This research extends the tiered assessment approach previously published for simply supported beams so that it is now applicable to composite beams with any number of spans, span lengths, shear connection distribution and cross-section. The technique is validated using a finite element program developed to model the behaviour of composite structures and the procedure is demonstrated in an illustrative assessment.