Modified strut and tie model of headed stud shear connectors in open trough profiled sheeting for predicting the post cracking load bearing resistance

in ce/papers (2021), 4(2-4), 627-634

Current EN 1994-1-1 provides statistically calibrated equations for predicting the strength of headed stud shear connectors in profiled steel sheeting. Recent tests showed that the design re-sistance is ... [more ▼]

Current EN 1994-1-1 provides statistically calibrated equations for predicting the strength of headed stud shear connectors in profiled steel sheeting. Recent tests showed that the design re-sistance is overestimated for some novel open trough decks. A mechanical model was developed within the RFCS Project DISCCO [3] that considers “stud in bending” component and the elastic bending resistance of the concrete rib separately (1-2 mm slip). However, to represent the behav-iour of the connector in the post-cracking stage (2-6 mm), a “Modified Strut and Tie” model was developed with the support of experimental and numerical results. The concrete and the steel deck were replaced by a system of strut and tie elements whereas the stud was considered as a beam with one or two plastic hinges. In accordance with test observations, the authors assumed that the resistance of the model is limited by the capacity of the strut in front of the stud estimated through an analogy with RC corbels. The analytical resistance of the system was finally derived and compared with the results of 193 push-out tests: the statistical evaluation delivered a corre-lation coefficient of 0.81 and a coefficient of variation of 0.15. [less ▲]

Different load‐bearing mechanisms in headed stud shear connections in composite beams with profiled steel sheeting

in ce/papers (2019, September), 3(3-4), 231-236

The current regulations of EN1994-1-1 for headed stud shear connections in composite beams with profiled sheeting lead, for some configurations, to an over-estimation of the load-bearing capacity. Since ... [more ▼]

The current regulations of EN1994-1-1 for headed stud shear connections in composite beams with profiled sheeting lead, for some configurations, to an over-estimation of the load-bearing capacity. Since these design equations are based on empirical considerations, they are not able to capture the real mechanical behaviour of the connector and they do not consider appropriately the influence of the geometry of sheeting on the shear capacity. For this reason, the load-bearing mechanisms of the shear connection are identified in this work with the support of experimental and numerical results. According to the static system presented, the concrete rib is modelled as a system of diagonal struts acting simultaneously in combination with the stud in bending. It is observed that at 2÷4 mm slip, a ?Strut and beam? mechanism prevails where the resistance of the connector depends mostly on the plastic hinges activated in the stud and on the capacity of the diagonal strut in front of it. By increasing the slip (ca. 4÷10 mm), the surrounding concrete progressively crushes while the tensile stresses at the edge of the rib reach the tensile strength of the material. As a consequence of this loss of rotational stiffness, the bending capacity developed in the stud reduces and the upper hinges gradually moves towards the slab. At higher displacements (ca. 20÷40 mm), due to nonlinear geometric effects, high tensile forces develop in the stud and the load is carried through a ?Strut and Tie? resistance mechanism, if the embedment of the stud is sufficient. By further increasing the slip, the whole rib rotates or the failure occurs either for concrete pull-out or stud rupture. This contribution describes the sequence of the activated load-bearing mechanisms in headed stud shear connections with profiled steel sheeting at different displacements. [less ▲]

Equations to predict the shear connection capacity of composite beams with slender profiled steel sheeting

Scientific Conference (2019, July)

The rules of EN1994-1-1 for shear connections in composite beams with deep profiled sheeting sometimes lead to an overestimation of the load bearing capacity of the respective shear connection. The ... [more ▼]

The rules of EN1994-1-1 for shear connections in composite beams with deep profiled sheeting sometimes lead to an overestimation of the load bearing capacity of the respective shear connection. The estimation of the impact of the sheeting shape on the calculated connection resistance is based on test results from the late seventies until the early nineties. Meanwhile, new products have appeared on the market with the target to reduce the volume and weight of the concrete in order to maximize the slab efficiency. However, the corresponding effects onto the shear connection have been underestimated because the use of deeper and more narrow deck rib lead to a more slender profile with a changed failure behaviour. Instead of the shearing-off failure of the stud, a combination of concrete cone failure and plastic bending of the stud – with one or two plastic hinges - was identified in laboratory tests. Based on the observed failure mechanisms, a new mechanical model with respective analytical equations for the shear resistance of headed studs in profiled steel sheeting was proposed. The new model extends the yield hinge mechanism, which was developed by Lungershausen [1], to more precisely predict the formation of the number of yield hinges depending on the mechanical and geometrical properties with the support of a finite element model. The complete equations consider the geometry of the stud and the steel decking as well as the material strengths of the stud and concrete. The statistical evaluation shows a good accordance with the developed model and analytical design equations. This contribution presents the new design equations and their background describing the mechanical model, the numerical study and statistical evaluation of push-out test results. [less ▲]

Serviceability performance of steel–concrete composite beams

in Proceedings of the Institution of Civil Engineers : Structures and Buildings (2017), 170(2), 98--114

The use of steel–concrete composite beams in which wide-flanged steel beams act compositely with a concrete or steel–concrete composite slab above is well established in building construction. However ... [more ▼]

The use of steel–concrete composite beams in which wide-flanged steel beams act compositely with a concrete or steel–concrete composite slab above is well established in building construction. However, for composite beams with low degrees of shear connection between the beam and slab, significant additional deflections can occur due to slip in the shear connectors. A design formula is presented for the effective stiffness of composite beams taking account of the stiffness of the shear connectors, which is compared to measured deflections of six symmetric composite beams and an 11 m span composite beam of asymmetric profile. It is shown that... [less ▲]