Experimental research on precast encased composite beams with welded shear studs under high-cycle fatigue loading

Due to their outstanding performance, the application of precast encased composite flexural members is becoming increasingly widespread in large-scale infrastructure. There is a lack of research or design guidance on the fatigue performance of precast encased composite beams having welded-on shear studs (ECB-S), making it difficult to accurately evaluate their fatigue behavior. This paper reports an experimental study of the high-cycle fatigue behavior of ECB-S subject to flexure. The fatigue failure process, development of strain and deformation, fracture morphology and fatigue life were examined. The similarities and differences of fatigue performance between ECB-S and bare steel beams, as well as encased composite beams having no welded anchors, were compared. The study illustrates the expected behavior of such ECB-S as being governed by the fatigue behavior of the reinforcing bars present in the embedding concrete; behavior is well-predicted by existing relationships for reinforcing bar fatigue in concrete. Upon fracture of the reinforcing bars, forces are redistributed to the embedded steel section, increasing the stress range on this element whose subsequent fatigue performance is affected by the presence of welded on studs – behavior also well-predicted by existing relationships. Evaluation of a larger data base of comparable test results reinforced the findings of the experimental portion of this study and allowed design recommendations to be presented for ECB S. This study provides a reference for the engineering application of ECB-S under fatigue conditions.