Minimum degree of shear connection in composite beams in buildings

Composite beams are often used in building construction with spans normally ranging between 6 to 18m. They are commonly used together with decking of 50 to 80mm depth that spans 3 to 4.5m between the beams. Rules for the minimum degree of shear connection in composite beams are presented in Eurocode4 and other international Codes, and were derived for beams propped in construction. Eurocode4 defines a minimum limit for the degree of shear connection, primarily to ensure that slip at the steel-concrete interface does not exceed a limiting value. This limit is proportionate to the beam span and also depends on the steel grade and the asymmetry in the flange areas of the section. Currently, many designs cannot achieve the codified minimum degree of shear connection, since it is not possible to accommodate a sufficient number of shear connectors on the span as dictated by the spacing of the deck ribs. However, there are special cases which are not explicitly accounted for in Codes. This paper aims to investigate the degree of shear connection requirements in such cases, including beams that are unpropped in construction, beams that are not fully utilised in bending because serviceability criteria govern their design and beams that are predominantly loaded by point loads rather than uniform loading. Parametric finite element (FE) analyses were carried out for composite beams in the span range of 9 to 18m and the results are presented. The finite element models have been validated against composite beam tests. Comparisons are made with the current Eurocode4 provisions and modifications are proposed where appropriate. (Author)