Why are the main and main beam joints of steel structures articulated?
If there is only one side of the beam, the beam bending moment into girder bending moment, for the opening section, the torsional ability is not strong, the box section can be made rigid, but the torque for an I-shaped cross section is best not to. For the main beam with both secondary beams on both sides, the bending moment at the joint of both sides of the secondary beam is small, and the bending moment on both sides can be counteracted each other, and it is feasible to make a rigid connection. But in fact, the existence of live load may cause a great difference in the bending moment between the two sides, so it is possible to produce a larger torque when the rigid joint is used.
Cross section of girder and beam is generally not the same, a lower flange of girder to girder webs, a lower flange to transfer moment is more difficult to achieve
The hinged construction is convenient, the requirements of the secondary beam are large, the maximum bending moment is in the midspan, and the torsion resistance of the rigid beam is high.
