Steel–Concrete Composite Beams Considering Shear Slip Effects

TLDR

Slip effects are largely omitted in most design specifications, although the AISC provides a slip‑accounting procedure in its commentary. This study investigates how shear slip influences the deformation of steel–concrete composite beams. The authors derived a general slip‑adjusted rigidity formula from equilibrium and curvature compatibility, validated it against six test specimens and existing data for simply supported and continuous beams, and compared it with the AISC effective‑section approach. Accounting for slip markedly improves prediction accuracy, can reduce stiffness by up to 17 % in short‑span full composite beams, and shows that AISC specifications are conservative for partial composites but not for full composites.

Abstract

The present study investigated the effects of shear slip on the deformation of steel–concrete composite beams. The equivalent rigidity of composite beams considering three different loading types was first derived based on equilibrium and curvature compatibility, from which a general formula to account for slip effects was then developed. The predicted results were compared with measurements of six specimens tested in the present study and other available test results for both simply supported and continuous beams. It was found that including slip effects has significantly improved the accuracy of prediction. For typical beams used in practice, shear slip in partial composite beams has a significant contribution to beam deformation. Even for full composite beams, slip effects may result in stiffness reduction up to 17% for short span beams. However, slip effects are ignored in many design specifications that use transformed section method except that American Institute of Steel Construction (AISC) specifications recommend a calculation procedure in the commentary. In the AISC procedure, stress and deflection calculations of partially composite girders are based on effective section modulus and moment of inertia to account for slip, while ignoring slip effects in full composite sections. For full composite sections, the effective section modulus and moment of inertia calculated with the AISC specifications are larger than that of present study, meaning that the specifications are not on the conservative side. For partial composite sections, the AISC predictions are more conservative than the present study.