The safety of shelving systems is paramount in warehouse management. As the primary and secondary frames serve as the load-bearing structures, their design, manufacturing, and installation must strictly adhere to rigorous safety standards and regulatory requirements. Numerous domestic and international standards organizations have established technical specifications tailored specifically for shelving systems—covering not only overarching design principles but also the unique demands of individual components such as main and secondary frames. Understanding and implementing these standards is crucial for ensuring safe warehouse operations and preventing potentially catastrophic shelf collapse incidents.
 

The international shelf safety standard system primarily includes standards such as the European FEM standard, the U.S. RMI standard, and the Japanese JIS standard. Among these, FEM 10.2.02 "Static Steel Rack Design for Pallets" and FEM 10.2.03 "Safety Guidelines for Static Steel Racks and Shelf Racks" are widely adopted European standards for rack design, outlining detailed requirements for load distribution between primary and secondary frames, as well as calculations related to structural strength and stability. Meanwhile, the 2002 U.S. standard from RMI (Rack Manufacturers Institute) specifies design, testing, and application guidelines for industrial steel racks, with particular emphasis on the specialized design requirements for primary frames as independent support units. Although these international standards are not mandatory, they are widely embraced by leading global rack manufacturers, serving as industry benchmarks for technical excellence.
 

Although China currently does not have a unified national standard for shelving systems, several industry standards and technical specifications already exist to guide the design and manufacturing of shelving. For instance, the machinery industry standard JB/T 5323-91, "Technical Specifications for Design of Welded Steel Structural Shelves for Automated Warehouses," and ZBJ83015-89, "Code for Design of Rail-Guided High-Rack Warehouses," outline specific technical requirements for the main structural components of shelving systems, including primary and secondary frames. Additionally, the CECS 23:90 standard from the China Engineering Construction Standardization Association, titled "Code for Design of Steel Shelving Structures," provides essential guidelines for shelving structure design—covering aspects such as load calculations, strength verification, and connection design. Although some of these standards have been in place for many years, they continue to serve as crucial references for domestic shelving design and manufacturing in the absence of a comprehensive national standard.
 

The special requirements for the main frame design stem from its independently supporting nature. As the primary load-bearing component of shelving systems, the design load for the main frame should account for dead loads (the weight of the shelving itself), live loads (the weight of stored goods), vertical impact loads (resulting from dynamic effects caused by forklift operations), and seismic loads, among others. According to the ANSI/MH10.2-1984 standard, industrial steel shelving systems typically require a safety factor of no less than 1.5, though this requirement may be even higher for the main frame. In terms of material selection, the upright posts of the main frame are usually made from higher-strength steel with thicker walls compared to those used in secondary frames, ensuring superior independent stability. Additionally, the connections between the main frame’s crossbeams and upright posts must incorporate safety pins or self-locking bolts to prevent the crossbeams from detaching under external impact forces. Furthermore, the base design of the main frame is engineered to be more robust, often featuring larger base plates and an increased number of anchor bolts to guarantee a secure and reliable connection with the floor.
Although the standard requirements for secondary rack design are slightly lower than those for the main rack, special regulations still apply due to its reliance on the main rack for support. When designing the secondary rack, it’s crucial to focus on the connection strength with the main rack and the efficiency of load transfer. According to FEM standards, the design load for the secondary rack should account for both the weight of the goods it carries and the portion of the load transferred to the main rack. Additionally, the connection nodes between the secondary and main racks must be capable of withstanding significant bending moments and shear forces, ensuring they remain intact even under uneven loading conditions or in cases of forklift collisions. Although the secondary rack has fewer upright columns compared to the main rack, each individual column is typically specified with the same dimensions as those used in the main rack, guaranteeing adequate local load-bearing capacity. It’s worth noting that the length of the secondary rack—measured along its depth direction—should generally not exceed 1.5 times the length of the main rack, to prevent excessive eccentric loads from being imposed on the main structure.

Safety considerations for the main and auxiliary frame combination system must be addressed from an overall structural perspective. When the main and secondary frames are connected to form a continuous shelving system, their mechanical performance differs from that of standalone shelves, necessitating careful consideration of both overall stability and localized strength coordination. According to the CECS 23:90 standard, composite shelving systems must undergo comprehensive lateral displacement calculations to ensure they remain structurally stable under horizontal loads—such as seismic forces or impact loads—without experiencing global instability. At the same time, the strength at the connection points must exceed that of individual components, adhering to the design principle of "strong nodes, weak members." In practical applications, the safety factor for combined main-and-secondary frame systems should be higher than that of independent main frames, as multiple support points share the load collectively, thereby reducing the stress levels on individual components.

The quality standards for shelf installation directly affect the safety performance of both main and secondary shelves. According to industry standards, the maximum vertical deviation of the uprights in modular shelving systems should not exceed 1/120 of the total height, while for integrated warehouse-shelf systems, the vertical deviation of the uprights must be kept within 1/1000 of the total height—and the absolute vertical deviation should remain below 10 mm. These stringent requirements ensure the stability of high-rise shelving units. During installation, the main frame should be assembled and leveled independently first, followed by the sequential installation of secondary frames, ensuring uniform tightness of bolts at each connection point. After completion, a comprehensive inspection is required, covering aspects such as the verticality of the uprights, the horizontality of the crossbeams, the reliability of bolt connections, and the effectiveness of safety devices. For heavy-duty shelving systems, a load test must also be conducted to verify that the system’s load-bearing capacity meets the design specifications.

Safety guidelines for daily use are equally important for both the main and secondary support systems. Shelves should be inspected regularly, with a particular focus on the connection points between main and secondary frames, the verticality of upright posts, and any deformation in crossbeams. Units responsible for using the shelves must strictly adhere to the designed load capacity—overloading is strictly prohibited. In particular, since the main frame serves as the primary load-bearing unit, its actual load should not exceed 80% of the design value. In forklift operation areas, the main frame should be equipped with collision-resistant guardrails and corner protectors to minimize the risk of impact. When adjustments to the shelf configuration are necessary, the "main frame first" principle must be followed: Any movement or reconfiguration must begin with the main frame, ensuring the integrity of both the main and secondary frames and preventing unstable structural conditions caused by moving the secondary frame independently.
Safety considerations in special environments require extra attention. For areas prone to earthquakes, the connection between main and secondary racks should incorporate seismic-resistant designs, such as increasing the area of connecting plates or using抗震 bolts. According to GB50011—2001 Code for Seismic Design of Buildings, shelf systems must account for the effects of horizontal seismic forces. In high-humidity or corrosive environments, both main and secondary racks need enhanced anti-corrosion treatments, such as using galvanized steel sheets or increasing coating thickness. Additionally, in low-temperature conditions, the brittleness of steel materials increases; therefore, the main rack, as a primary load-bearing component, should be made from materials with excellent low-temperature toughness to prevent brittle fractures.

The future trend in safety standards will place greater emphasis on the overall performance and intelligent monitoring of shelving systems. With the advancement of IoT technology, main racks may integrate sensors to continuously monitor load distribution, structural deformation, and connection status, enabling early detection of potential safety hazards. Meanwhile, the application of new materials—such as high-strength aluminum alloys and composite materials—will redefine design standards for both main and secondary racks, making shelves lighter yet stronger. Additionally, as automated warehousing becomes more widespread, safety standards for shelving systems will increasingly focus on seamless coordination with human-machine interaction interfaces, ensuring safe and efficient collaboration between automated equipment and the shelving system. These developments will lead to more scientific, secure, and efficient designs for both main and secondary racks.