The grid is divided into a plurality of strip or block units from the plane, and after each strip (block) unit is assembled on the ground, it is then hoisted by the crane to the design position to form a whole, and this method is called the strip (block) hoisting method.
1.Process characteristics
The strip element is generally divided in the direction of the long span, its width is about 1 3 grids, and its length is L2 or L2 2 (L2 is the short span span). Block units are generally divided into rectangular or square units along the longitudinal and transverse direction of the grid plane. The weight of each unit is subject to the capacity of the existing crane. The strips (blocks) can be assembled directly between the strips (blocks), or they can be assembled at high altitude with an empty grid. Because the strip (block) unit is assembled on the ground, the amount of aerial work is greatly reduced by the high-altitude bulk method, and the assembling support is also reduced a lot, and the existing lifting equipment can be fully utilized, so it is more economical. This installation method is suitable for all kinds of small and medium-sized grids that the stiffness and stress condition of the grid after segmentation change little, such as two-way orthogonal quadrangular pyramid, positive evacuation quadrangular pyramid and other grids.
2.There are several ways to divide the unit into strips (blocks) as follows:
1) The units are close to each other, and the lower chord is divided into two units with double angle steel, which can be used for placing the quadrangular pyramid grid.
2) The units are close to each other, and the upper chord is connected by a split installation node, which can be used for oblique quadrangular pyramid grid.