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About the selection of heavy-duty shelf columns

About the selection of heavy-duty shelf columns

How to choose heavy shelf columns! Heavy-duty shelves are an important carrier for improving warehouse efficiency and enhancing warehouse access efficiency, and have been used more and more widely in various industries. The detachable shelf is also called the combined shelf. The height of the shelf can be adjusted arbitrarily according to the pitch, so that the layer spacing of the shelf can be adjusted arbitrarily with the size of the placed goods, increasing the randomness and flexibility of the inventory, and having a small component size and a warehouse. The utility model has the advantages of high utilization rate, convenient production, interchangeable assembly and short installation period, and has become the most widely used one in the shelf.

The column is the ultimate bearing component of the detachable shelf, and its design is the key to the entire shelf system, directly related to the safety of the structure and the economics of use. The assembled shelves are mainly composed of basic parts such as column pieces and beams, and optional parts such as corner guards, corners, spacers, partitions, and laminates (steel plates or planks). The column piece is the main force supporting part of the shelf, and the load can be up to 21 tons. With the increase of the height of the shelves and the increase of the number of layers, the columns are loaded, and most of them adopt cold-formed and thin-walled steel. The residual machining stress remains, and the actual stress is complicated. Therefore, the design of the column becomes the whole. The key to the racking system is directly related to the safety of the structure and the economics of use.

First, the cross-sectional shape of the column

From the cross-section, there are many cross-sectional shapes of the column, but in terms of current market distribution, basically the mainstream profiles are still the basic type of stable shelves, and some of the profiles are relatively simple, mainly used for lightweight shelves; The rolling structure is relatively complicated, and the processing technology is relatively complicated, and is mainly used for medium and heavy-duty shelves. Other shapes derived from the basic type are mainly to increase the bending on the longer length side to improve the rigidity and stability of the column. In terms of specific design, in addition to considering the strength, stiffness and structural stability, the influence of the specific molding process on the hole type and the influence of the pre-machining condition of the blank on the product quality, such as pre-punching and not cold bending, should generally be considered. The influence of the bending deformation on the roller line on the product quality, the possible deformation of the pre-punching hole during the cold bending process, and the like. Under the premise of ensuring the dimensional tolerance requirements and ensuring the hole spacing requirements, the design of the section shape should take into account the requirements of different plate thicknesses, and the deformation adopts a fixed bending radius.

Second, the beam hanging hole

The front side of the column is evenly distributed with a number of long holes (hook holes) and round holes for hooking the beams and installing safety pins.

The hole type usually adopts inverted eight-word, diamond shape or inverted trapezoid, so that the long hole of the column has a small angle with the vertical direction. After the hook is hung up, it is automatically locked under the action of the gravity of the cargo, and the hook is in surface contact with the long hole of the column. The stress state is better, ensuring more stable and safe use. However, the opening of the hook hole has a great influence on the bearing capacity of the short column of the column, and the bearing capacity after the opening is 70% to 95% of the bearing capacity when the hole is not opened, and the influence on the small-sized column is greater. Therefore, under the condition that the load capacity of the beam hook is satisfied, the size and number of the hook holes should be made as small as possible to improve the overall load carrying capacity of the shelf.

Third, the design check

Since the column is the main force-bearing part of the shelf, the structure is relatively complicated, and most of them adopt cold-formed thin-walled steel (there is a certain processing stress remaining in itself), and the load condition is also complicated, especially the high-rise shelves, the number of layers is large, The load is large, so that the design of the column is tedious, the check is complicated, and the value is reasonable, which is directly related to the safety of the structure.

Fourth, the strength and stability check

1. Strength calculation: When the shelf is checked for strength in the opposite column, according to the different loading state, it is necessary to check the calculation according to the axial compression member and the compression member. The calculation adopts the Technical Specification for Cold-formed Thin-walled Steel Structure (GB50018). -2002) related formula.

2. Stability calculation: Although the column of the shelf is basically made of cold-rolled steel sheet, the section of the column is bent many times, and there will be no local instability, but with the continuous enrichment of the cross-section of the shelf pillar and the high-strength steel The application makes the pressed column develop toward the light and thin wall, which easily causes the overall instability of the column, so the stability of the pressed column member is more important.

3. Analysis and calculation have confirmed that the mechanical properties of the materials used in the column, the design of the mold, and the precision of the fabrication are the main factors affecting the bearing capacity and stability of the column. The size changes of various pore types have a direct impact on the stability. Local thinning of the cross section of the material has little effect on stability.

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