Mechanical Model to Predict the Resistance of the Shear Connection in Composite Beams with Deep Steel Decking

in Eurosteel 2017 (2017, September 13)

The resistance of a typical shear connection with headed shear studs in a composite beam is analysed in the normal case in accordance with EN 1994-1-1. The reducing effect of a trapezoidal metal decking ... [more ▼]

The resistance of a typical shear connection with headed shear studs in a composite beam is analysed in the normal case in accordance with EN 1994-1-1. The reducing effect of a trapezoidal metal decking onto the ultimate load bearing capacity is considered with empirically derived reduction factors and equations, which have been developed in the last century between the late 70th and the early 80th. The RFCS research project “DISCCO” investigated the shear stud resistance with novel types of steel decking. In many cases, the shear resistance, which was predicted by EN 1994-1-1 was not reached in tests. In the respective experiments with composite beams and deep decking, a concrete cone failure mode was identified and not a pure shear failure of the stud. This failure mode acted in combination with the load bearing capacity of the shear stud, which formed one or two plastic hinges in the shaft - depending on the available geometry. Based on these observations, new equations have been developed to predict the shear connection’s resistance with more accurcy. The yield hinge mechanism of the shear stud, which was developed by Lungershausen, was extended by the above mentioned load bearing component ‘concrete cone’. The formulae consider the geometry of the stud and the steel decking, the material strength of the stud and of the concrete material. The statistical evaluation of the developed equations shows a good accordance with test results. [less ▲]

Influence of transverse loading onto push-out tests with deep steel decking

in Journal of Constructional Steel Research (2017), 128

This paper presents the results of 20 push-out tests on shear stud connectors, placed centrally in the ribs of 58 mm and 80 mm deep steel decking. The tests were designed to investigate the realistic ... [more ▼]

This paper presents the results of 20 push-out tests on shear stud connectors, placed centrally in the ribs of 58 mm and 80 mm deep steel decking. The tests were designed to investigate the realistic load–slip behaviour of the shear connectors and the influence of transverse loading. The tests considered two different stud diameters and the effect of concentric and eccentric transverse loading. In addition, the influence of a second layer of reinforcement, thewelding procedure and the number of shear connectors in each rib have been considered. The observed influence of these parameters on the load–slip behaviour is presented and explained with regard to material properties and load-bearing models. In addition, the test results are compared with the current analytical approaches,which are shown to be non-conservative in some cases, because the presented deck shapeswere not well considered in the development and calibration of EN 1994-1-1. [less ▲]

On the behaviour of shear stud connections in composite beams with deep decking

Doctoral thesis (2015)

Steel-concrete composite construction has many advantages for the construction of multistorey buildings. The use of composite beams acting compositely with the floor slab achieves longer spans and reduces ... [more ▼]

Steel-concrete composite construction has many advantages for the construction of multistorey buildings. The use of composite beams acting compositely with the floor slab achieves longer spans and reduces the weight of the beams. The weight reduction can be further improved by replacing the solid concrete slab with a steel-concrete composite slab using steel decking. However, using composite slabs reduces the shear forces that are transferred between the slab and the beam. This is because the number of studs in the span is limited by the deck geometry. In addition, the load-bearing behaviour of studs in the ribs of composite slabs is different to studs in solid slabs and shows typically a reduced resistance per stud. Currently, [DIN EN 1994-1-1, 2010] applies an empirical reduction factor to the resistance of studs in solid slabs to analyse the resistance of studs in the ribs of composite slabs. A comparison to push-out test results shows that this formulae results in an unsatisfactory correlation. Furthermore, the reduction factor is unsafe in many cases with modern decking. The latest empirical reduction factors in [Konrad, 2011] are currently discussed as alternative to the rules of [DIN EN 1994-1-1, 2010]. They show a significantly improved correlation to test results and an increased field of application. A significantly higher correlation to test results is obtained with the mechanical model by [Lungershausen, 1988]. Because of the restrictive field of application and missing parameters, like the concrete strength, it is not discussed as replacement for the reduction factors. A newly conducted series of push-out tests with modern deep steel decking shows the insufficiency of the presented analysis methods of the stud shear resistance, as the predictions were in general non-conservative. Furthermore, depending on the geometry of the shear connection, a new failure mode was observed: Rib pry-out failure. Investigation on concentric and eccentric transverse loading of push-out specimens, to consider the loading conditions of a real slab, show in general beneficial influences on the load-slip behaviour. Based on the behaviour of the studs in push-out tests, equations for the shear connector resistance based on the failure modes are developed. A combined bending failure of the shear stud and the concrete rib is assumed. The observed failure modes in the tests are considered by different yield-lines of the shear stud. The shear resistance of the pure stud gives the upper bound for the shear connector resistance. The new equations show a good correlation to test results and are safe for modern types of steel decking. In comparison to [DIN EN 1994-1-1, 2010], the field of application is extended by the stud position, as in [Konrad, 2011], and deeper decking, as in [Lungershausen, 1988]. The analysis of the bending resistance of two accompanying beam tests confirms the accuracy of the new shear stud resistance. The beam tests have very low degrees of shear connection. The end-slip at ultimate load exceeds the limiting slip of 6mm, but at 95% of ultimate load the limiting slip is satisfied. A numerical model for composite beams is verified against the test results. The model considers the shear studs as non-linear springs. A simplified load-displacement curve is presented and verified against real load-slip curves. [less ▲]

Push-out tests with modern deck sheeting to evaluate shear connector resistances

in Eurosteel 2008, 7th European Conference on Steel and Composite Structures (2014)