# Global Buckling Resistance of Cold-Formed Steel Beams with Omega-Shaped Sections
## 3 Experimental Campaign
### Test Setup  
The experimental tests followed the requirements outlined in Annex A.3 of EN 1993-1-3:2006 [2]. Consequently, the omega profiles 70 \(\times\) 1.5 and 170 \(\times\) 2.0 underwent testing using Layout 1, whilst the omega profiles 300 \(\times\) 2.5 were subjected to testing according to Layout 2.  
Layout 1 has a free span of 4.0 m, and the beam is simply supported at both ends. The profile is loaded at four points, as illustrated in Figure 1. The load transfer from the actuator is carried out through an IPE 100 beam supported by two metal plates with dimensions of 46 cm \(\times\) 10 cm \(\times\) 2 cm each. Each of these plates discharges onto two metal plates with dimensions of 15 cm \(\times\) 10 cm \(\times\) 1 cm, placed on neoprene bands, through rollers. LVDTs (extensometers) were positioned at mid-span and at the ends of the constant moment span, which has a length of 800 mm (corresponding to 20% of the total span between supports), as indicated in Figure 1a.  
Figure 1: Test setup with a 4-m simply supported span: (**a**) schematic representation of Layout 1, (**b**) photograph of Layout 1 for applying a downward load, (**c**) photograph of Layout 1 for simulating upward load application with continuous lateral and punctual bracings, and (**d**) detail of the load scheme, depicting the actuator, loading beam and plates, and neoprene bands located between the load plates and the profile.  
Layout 2 has a free span of 8.0 m, and the beam is also simply supported at both ends. Loading is applied at six points. The load transfer from the actuator is facilitated through an IPE 250 profile, supporting two metal plates with dimensions of 60 cm \(\times\) 10 cm \(\times\) 2 cm each. Each plate discharges onto three plates with dimensions of 15 cm \(\times\) 10 cm \(\times\) 1 cm, positioned on neoprene bands, through rollers. LVDTs (extensometers) were positioned at mid-span and at the ends of the constant moment span, which has a length of 2200 mm (corresponding to 27.5% of the total span between supports), as indicated in Figure 2a. All the tests were carried out by displacement control at a constant speed of 0.04 mm/s.  
The profiles underwent testing in both downward and upward directions. To simulate upward loading, it was necessary to apply an ascending load on the continuous element, corresponding to loading the profiles in an inverted position. Lateral bracing, as shown in Figure 1c,d, was essential in the inverted position to prevent profile instability. In Figure 1c, continuous and punctual bracing can be observed. Punctual bracing was implemented in four and five locations for the 170 \(\times\) 2.0 and 70 \(\times\) 1.5 profiles, respectively. For the medium profile, punctual bracing was applied at the supports and immediately after the occurrence of the maximum moment as it was not possible to restrain at the location of the maximum span moment where the loading plates are located. The smaller profile had the same punctual bracing as the medium profile, with an additional brace at mid-span.  
Figure 2: Test setup with an 8-m simply supported span: (**a**) schematic representation of Layout 2, (**b**) photograph of the test layout, and (**c**) detail of the loading scheme.  
Due to the geometrical characteristics of Layout 2 (see Figure 2b,c), it was not feasible to continuously brace the profile in an inverted position to simulate loading in an upward direction. Consequently, tests involving only downward loads were conducted with this layout.