Performance of Composite Steel-Concrete Beams with Stud Shear Connectors under Periodical Loadings

Abstract

Behavior of composite beams with headed stud shear connectors subjected to monotonous and displacement controlled non-reversible repeated loadings has been evaluated through studying influences of the cross-sectional proportioning, the degree of partial interaction, and the level of ductile deformability in the post-yielding stage, in addition to the state of loading (whether monotonous or repeated). Eleven one- third scaled composite beams (with their push-out segments) were manufactured and tested in five pairs (each comprising the two loading cases representing one varying studied parameter) beside the single standard composite beam dedicated to verify accuracy of the test results by comparing them to the prototype ones (three authorized experimental and analytical investigations) where no distinction (other than 7 % difference) between the results of the three authorized refereed investigations (experimental, analytical and Eurocode) and the present one.
Regarding the flexural resistance in repeatedly loaded composite beams, it has been found that lowering the neutral axis (by adding bottom steel plate) has significantly increased the beam flexural resistance by an average of 24.7 %. Meanwhile, the intensity of headed studs distribution in stiffened repeatedly loaded composite beams has revealed a vital role in controlling the severity of the post-ultimate flexural weakening, where decreasing number of the headed studs to the half has increased the value of that unfavorite parameter by 160.58%. Furthermore, that specified decrease of headed stud intensity has lowered the advantageous residual cyclic flexural ductility by 19.37 % and 11.48 % without and with stiffening bottom steel plates, respectively. Regarding the effect of the lengthening the headed stud on behaviour of the repeatedly loaded composite beams it has been found that lengthening the medium-length headed studs by 72% has raised the flexural stiffness by 41.1 %, while it has decreased the residual cyclic slippage index by 54.3 %.