## 3 Results and Discussion
### Plastification Mechanism  
At the design stage, a plastic hinge location was assumed from which the maximum forces at which the connection would be subjected were calculated. The test allowed us to show the plastification zone by visually placing it at the point with the greatest loss of the layer of lime. Additionally, an important concentration of stresses and large inelastic deformations in the plastic joint area at a distance of \(S_{\mathrm{h\_exp}}=480\) mm were observed in the tests.  
Figure 8a shows a comparison of the assumed position of the plastic hinge in the design stage and that obtained experimentally. From this, it is concluded that the position of the plastic hinge was 24% further away than the one initially proposed by the AASC 358-16 standard [4], which places it in the last row of bolts. The loss of the layer of lime indicates the plasticized areas of the beam, which are 50 mm from the edge of the diaphragm. It was  
observed that yielding began in the wings of the beam, and the yielding zone increased with each cycle of displacement until it was distributed over the web by 70%.  
During the test, yielding starts at the wings and spreads toward the web of the beam as the displacement increases in loading and unloading cycles (see Figure 8b). In the final displacement step, it was observed that the auxiliary beams that were aimed at guaranteeing adequate lateral support showed deformations outside the plane due to their low rigidity. Consequently, torsional lateral buckling occurred in the beam.  
Figure 8b illustrates the effect that describes the contact and separation of the auxiliary profiles attached to the test frame. In the upper right part of Figure 8b, this effect is observed at an amplified scale, which is one of the reasons why a failure was observed in the experiment due to local buckling only. As shown in Figure 8b, this failure occurred in one of the skates, after the maximum rotation imposed of 0.07 rad was reached.  
The reason why lateral support should be provided is to ensure that resistance degradation due to lateral torsional buckling is delayed until the connection reaches enough ductility and seismic energy is dissipated by deformation. During the experimentation, it was observed that in the last step of load application the auxiliary beams showed deformations out of the plane due to their lack of stiffness. Thus, torsional lateral buckling occurred in the beam. Nonetheless, this occurred at a 0.07 rad of rotation for a moment resistant capacity of 453.9 kNm. Therefore, the hysteresis diagram did not show a significant loss of resistance due to this phenomenon. Figure 9 shows the final state of the specimen during the test seen from different angles.  
The connection exhibited ductile hysterical behavior with stable cycles and large areas of energy dissipation. It should be noted that the inclusion of the diaphragms contributed to the good behavior of the connection. This is achieved by transmitting the compression and tensile stresses generated by flexion, which allows an adequate load distribution over a large part of the periphery of the column. In addition, a positive effect was observed when filling the column with concrete, since this decreased the possibility of local buckling as reported by [PERSON] and [PERSON] [34], and angular distortion due to deformation in the region of maximum shear stresses on the tubular column as reported by [PERSON] and [PERSON] [10].  
Figure 8: (a) Comparison of plastic hinge location according to design and experimental results; and (b) trial side view showing the torsional lateral buckling effect.