Behavior of Headed Studs in Composite Structures: An Overview

Composite structures have become integral to modern construction owing to their efficiency, strength, and economic benefits, with steel-headed studs serving as critical shear connectors between concrete slabs and steel beams. Existing research has investigated these connectors through push-out and pull-out experiments, fatigue and cyclic protocols, durability and temperature-extreme studies, and a wide range of analytical, numerical, and data-driven models. This study addresses the lack of a consolidated and critical review by combining a systematic review with a bibliometric assessment of 385 Scopus-indexed publications from 2000 to 2025, which shows sustained growth of research output and concentration of highly cited contributions in leading composite-structures outlets. The systematic synthesis highlights that stud performance depends strongly on geometry, grouped-stud interaction, and the surrounding cementitious matrix, and it shows that advanced concretes mixes often increase peak resistance while shifting governing failure toward stud or weld-related mechanisms. Design-code comparisons reported in the reviewed literature indicate that resistance predictions may deviate substantially in ultra-high performance concrete configurations, which supports the need for mode-aware provisions rather than direct extension of normal-concrete formulations. The modeling review identifies a progression from empirical equations toward nonlinear finite element simulation and interpretable machine learning trained on large databases, while noting that design adoption requires transparent applicability limits and physically consistent predictors. The paper concludes by consolidating design implications and by defining targeted research priorities on grouped studs, mixed-action fatigue, durability degradation factors, and interpretable data-driven tools for code-oriented design of composite shear connections.