Investigations on the lateral-torsional buckling of an innovative U-shaped steel beam in construction stage of composite beam

in Structures (2022), 44

Structural elements of building have to meet a multitude of requirements. Besides the static load bearing capacity, common requirements are the structural integrity and efficiency during the construction ... [more ▼]

Structural elements of building have to meet a multitude of requirements. Besides the static load bearing capacity, common requirements are the structural integrity and efficiency during the construction stage and sufficient fire resistance. Within the French CIFRE research project COMINO, an innovative type of composite beam was developed for buildings beams with a span of 6 -12m, which need fire resistance until 2 hours with no additional supports at construction stage. The developed solution is composed of a steel U-section acting as a formwork in construction stage for a reinforced concrete part that provides the fire resistance. In the exploitation stage, the steel and the reinforced concrete are acting together as a composite beam. In construction stage, when the concrete is not hardened and thus the stabilizing effect is not present, the steel beam, is subjected to Lateral-Torsional Buckling. In order to investigate the structural behaviour of the new developed steel section in construction stage, a single full-scale test has been carried out at the Laboratory of Structural Engineering of the University of Luxembourg. This article focuses on the stability of the steel beam made of thin-walled steel parts without considering any stabilizing effect. The test results are then compared to the results of numerical investigations and to the analytical solutions of EN 1993. [less ▲]

Numerical evaluation of the plastic hinges developed in headed stud shear connectors in composite beams with profiled steel sheeting

in Structures (2019), 21

For composite beams using novel steel sheeting, the current Eurocode 4 rules sometimes overestimate the load-bearing capacity of headed stud shear connectors. This is due to the larger rib heights and the ... [more ▼]

For composite beams using novel steel sheeting, the current Eurocode 4 rules sometimes overestimate the load-bearing capacity of headed stud shear connectors. This is due to the larger rib heights and the smaller rib widths in comparison with the old studies, which have been carried out to calibrate the current design equations. The RFCS Project “DISCCO” investigated this phenomena and the working group under mandate M515, CEN/TC250/SC4/SC4.T3 is enhancing this equation and working on a proposal to be taken over in the new version of Eurocode 4. The proposed new equation covers the failure behaviour of the shear connection more in detail. The test results show, that the failure consists in a combined concrete cone and stud in bending. Due to the geometry of novel steel sheeting, the load bearing capacity of the headed stud shear connector is no more limited by its shear capacity, but by its bending capacity. A 3D non-linear finite element model is developed and validated through the support of the DISCCO push-out tests. A good agreement between numerical and experimental results in terms of force-slip behaviour is achieved. Special attention of this work lies on the numerical evaluation of the number of plastic hinges n y : a stress-based procedure is presented and the results are compared to the equations presented for new Eurocode 4. The numerical simulations show that the upper plastic hinge moves up as the slip increases due to the progressive crushing of the concrete in the rib. From the parametric study, it turns out that n y is linearly proportional to the embedment depth. Compared to pre-punched hole decking, through-deck welding specimen activates less plastic hinges in the studs because of the higher stiffness provided at the base of the stud. [less ▲]

Characterisation of a new flat mechanical shear connection mean for steel-concrete composite columns

in Structures (2019)