1.Roof horizontal bracing system
The horizontal bracing of the roof is generally composed of a cross bar and a rigid tie rod.
In the portal frame light steel structure building, the cross bar of the roof horizontal bracing can be designed as round steel, but the tensioning device should be added to facilitate the tension of the tie rod to avoid excessive deflection of the round steel. The cross bar can also be designed as angle steel, but it is also necessary to consider the deflection of the long support due to its own weight and should take the necessary measures to overcome it. The angle between the cross bar and the vertical bar should be in the range of 30 ° ~ 60 °. The horizontal bracing of the support rod is made of angle steel, and the connection point is similar to the ordinary steel structure. The key is to ensure that the rod must intersect at the node. The nodes made of tensioned round steel rods can be connected by a single bolt.
The rigid tie rods can be made of steel pipe or double angle steel. Small spans and heights building , the purlins can be used concurrently, but the purlins need to be pressed against the curved member design, and the slenderness ratio and stability outside the plane of the purlins should be ensured.
(2)Column Cross Bracing
Column Cross Bracing In the case of a low height building, a cross-shaped tie rod can be made of round steel with a tensioning device. Angle or channel steel can also be used.
In tall buildings, the cross bars supported between the columns can be steel pipes in addition to angle steel. The steel pipe has the advantages of material saving, simple production, and is solid and beautiful in the building.
The connection nodes between the columns are similar to the horizontal supports. It must be noted that the upper end of the column bracing and the horizontal strut must be at a point with the center of the column. Similarly, the lower end of the column bracing should be placed as close as possible to the bottom of the column to avoid eccentric stress. If the adjacent columns of the column bracing need to share the horizontal reaction force, a pressure bar should be added between the two columns, and the steel bar can be used for the pressure bar. If the column foot is above the ground, a reinforced concrete beam can be placed under the ground.
(3) Flange Bracing
The flange bracing is generally made of angle steel. The angle between the rafter and the rafter or wall girt should not be less than 35°. The minimum angle is L50*4 angle steel. Bracing bolts are connected to beams or side columns and purlin or wall girt.
Under normal circumstances, the roof beam should be set in the full span of the column and roof beam, mainly considering the possibility that the flange is pressed under the wind load, and it can be set only in the area where the lower flange of the beam is pressed near the bracing system.