*2.3. Experimental Model—Specifications of the Measurements*

Experimental analyses were conducted in the testing machine as presented in Figures 1 and 2. The displacement increment over time of the top fastening element of the machine (node 2) was assumed constant. Displacements (node 2), forces (node 4) and time were measured. Additionally, the changes of strains in selected points and directions of the trapezoidal sheeting in relation to the

time were registered. The layout of the strain gauges used in the tests is presented in Figure 4. SG 1 and 5 registered the changes of the strains in the direction perpendicular to the corrugations in the side of the middle corrugation, 50 mm from the frame edge (on both sides of the sheeting). SG 2, 3 and 4 formed a rectangular rosette (on one—bottom side of the sheeting) which allowed us to assess principle stresses (assuming elastic modulus *E* = 210 GPa).

**Figure 4.** Strain gauge (SG) measurements: (**a**) scheme of the SG location; (**b**) SG 5 during the test; (**c**) SG 1, 2, 3 and 4 during the test. '

Four tests of trapezoidal sheeting panels were conducted. The test 1 assumed the displacement was increasing constantly until the panel failure. In tests 2, 3 and 4 the repeated displacement increase/decrease was implemented. The loading protocol in tests 2, 3 and 4 was as follows:

• Initial force 50 N.


The initial force in the testing machine was 50 N. Nevertheless, in the initial stage of loading, the loose spaces of the set-up disturbed the measurements (about 3,5 mm and circa 300 N). In the paper diaphragms without this initial stage are analysed.
