Knee bracing refers to the support rod between beam and purlin, and between column and purlin. The wall on the wall is called wall knee bracing, and the roof on the roof is called roof knee bracing.
The function of knee bracing:
(1) In order to ensure the out of plane stability of the component and reduce the calculation length of the component out of plane. When the inner flange of beams and columns needs to be set with lateral support points, purlins or wall beams connected to the outer flange can be used to set corner braces. Corner braces are generally made of single angle steel and designed as axial compression members.
(2) It is set to prevent buckling and instability of compression flange (lower flange of beam and inner flange of column) and increase the stability of compression flange. The angle brace is used to ensure the local stability of the compression part of the lower flange of the beam. The local stability of the upper flange of the beam is guaranteed by the purlin connected with it. Cause: the upper flange of the beam is the tension area, and there is no overall stability problem. However, there are some potential local stability problems to some extent, but generally, the lateral force caused by local instability is very small. Therefore, as a component connected with purlin, it can ensure the stability of flange.
For portal frame and steel frame, the upper flange of the beam is in tension at the support position, but in the middle of the span it is in compression. Therefore, the stability of the upper flange of the beam has purlin or floor slab connected with it to ensure its out of plane stability.
