What factors affect the quality of bolted ball space frames?

Steel space frame structures are a new type of structure that has been widely promoted and applied in the last ten years or so. They are composed of bolted ball joints and seamless steel pipes, and are statically indeterminate structures connected by high-strength bolts or welding. They possess characteristics such as low steel content, excellent seismic resistance, reduced construction time, and aesthetically pleasing design. They are widely used in large-span projects such as sports stadiums, airport terminals, high-speed rail waiting rooms, gas stations, factories, and large and medium-sized storage warehouses. However, in actual practice, two factors still affect the quality of bolted ball space frames during production, processing, and installation.

（1）Insufficient strength of high-strength bolts

The strength of high-strength bolts (which can bear a greater load than ordinary anchor bolts of the same specification) in bolted ball joint space frame structures is a key factor affecting the load-bearing capacity of the joints, and its strength is related to the surface strength.

（2）Inadequate Anchor Bolt Length

During installation, the length of the thread inside the bolt ball is obscured, making it impossible to accurately measure the thread length. Insufficient thread length poses a risk. This is similar to screwing in the threads of an assembly bed; if only 1/3 of the thread is screwed in, the risk is inevitable. Increasing the thread length allows for a more suitable space between the thread and the pitch, reducing the risk.

（3）Large Deviations in Bolt Ball Manufacturing

If the diameter, concentricity, unevenness of the milled surface, and thread deviations of the bolt balls are too large during manufacturing, the installation of the space frame will exceed allowable tolerances. This will cause the space frame dimensions and centerline to fail to meet design requirements, affecting the load-bearing capacity and leading to risks. Therefore, finding a space frame manufacturer that adheres to material quality standards is crucial.

(4) Large Deviations in Component Manufacturing

If the length, end alignment, pipe axis flatness, and midpoint line deviations of the space frame structure components exceed the standard allowable requirements, it will make assembly and installation of the space frame structures difficult, resulting in incomplete or forced assembly and installation. This leads to large deviations in geometric dimensions and component midpoint lines, failing to meet design specifications and thus affecting the load-bearing capacity of the space frame.

(5) Space Frame Structures Installation Quality

After installation, if additional hanging loads are applied to the space frame structure during use, causing deflection values ​​to increase, even exceeding the design value by 1.15 times, it will lead to serious risks. The surface of the space frame will also experience severe paint peeling and rusting within 5-10 years, resulting in poor appearance and threatening the structural integrity of the space frame. The quality of the raw materials for the production, processing, and installation of space frame structures directly affects the overall stability of the space frame structure and the safety of the public. Therefore, we should focus on the fundamentals from the beginning and select a reliable space frame manufacturing company to effectively reduce deviations caused by bolt ball space frame production and installation.