Interpretation of terms. Overall instability of steel beams (steel structures)

Beam is the main component of the structure, and the beam is in the state of bending moment.

Under the action, the upper flange is compressed and the lower flange is stretched. For the compressed upper wing

On the other hand, the flange plate with less stiffness has some buckling along the out-of-plane direction.

Trend, but the web and stable tension flange provide this.

The directional binding force prevents it from buckling in this direction.

When the flange pressure caused by external load is large enough, the flange can only be wound.

It is true for the whole beam that its own strong axis is buckled in plane.

The flange moves laterally, driving the connected web and lower wing at the same time.

The lateral displacement of the edge and the relative torsion angle of the whole section are generated, in which

It is said that beams have overall bending and torsion instability.