PSI - Issue 78

Agnese Natali et al. / Procedia Structural Integrity 78 (2026) 2015–2021

2019

The strain gauge measurements on the beams, illustrated in Fig. 6, indicate that yielding started in the tension flange of the beam subjected to sagging bending moments, followed by the simultaneous yielding of compressed flanges of both beams. Conversely, the tension flange of the beam under hogging bending moment — located just beneath the slab — remained within the elastic range throughout the test. Please note that the yield strain value indicated by dotted lines in the figure refers to the nominal value.

Fig. 6. Strain gauges measurements on IPE flanges (located as shown in Fig. 3).

Once a top displacement of around 210mm was reached at the top of the specimen, the tearing of the weld in tension between the passing-through plates and the CHS wall began. Support reaction forces remained largely balanced, with minor variation during loading, eventually converging at peak displacement. The moment-rotation diagram classified the joint as semi-rigid per Eurocode 4, exceeding the threshold for hinge classification (Fig. 7). Overall, the joint demonstrated good structural integrity and ductile behaviour up to the test limits, with controlled damage concentrated in the slab and weld zones.

Fig. 7. Joint moment-chord rotation diagram.