Key Points for Quality Control in the Manufacturing and Installation of Bolted Spherical Steel Truss Structures（II）

III.Process control for the installation of bolted ball steel grid structures

Bolted Spherical Grid Installation Process

Before installing the space frame, installers must be familiar with all the members, ball types, dimensions, and their positions in the drawings. Any deformation of members caused during transportation, storage, or lifting must be corrected. All members and balls must be marked. During installation, they must be carefully checked against the drawings to ensure accuracy before installation. The installation of space frames primarily involves the connection between bolts and spheres. The friction surfaces of components must remain dry. High-strength bolts must be smoothly inserted into the sphere holes, with consistent insertion direction. They must be tightened in two stages, and each set of high-strength bolts must be fully tightened on the same day, with no bolts left untightened. Different installation processes must be adopted for different space frame configurations. Space frame structures generally come in two forms: planar and curved. Their support methods include multi-point support, two-sided support, and perimeter support. In planar space frames, the upper chords are typically compression members, while the lower chords are tension members. Therefore, from a holistic perspective, the upper chords generally have larger combined specifications than the lower chords. Deformation caused by self-weight during truss installation often poses challenges for subsequent installation, particularly for large-span planar trusses. Therefore, sliding construction should not be encouraged for this type of truss installation. Full-span scaffolding provides the most advantageous construction platform for trusses, ensuring construction safety while also bearing part of the truss weight. This effectively prevents grid settlement deformation and addresses accumulated installation errors and deviations between supports and embedded components during the installation process. Curved space frames are equivalent to arch structures, with most of the radial members in the entire space frame being compression members (referring specifically to the upper curved surface type). The installation of compression members is more challenging than that of tension members. Before installation is complete, compression members should not be subjected to loads to prevent subsequent installation work from becoming impossible.



Bolted Spherical Grid Installation Error Control

Quality control in the installation of bolted ball steel space frames primarily focuses on controlling installation errors and preventing their accumulation. First, embedded components must be leveled and their axis lines marked to ensure that the supports meet the installation requirements specified in the design. Any embedded components that do not meet these requirements must be addressed promptly. Secondly, sufficient support points must be provided on the operating platform to prevent the entire truss from settling before it is fully formed, thereby failing to meet the ideal installation conditions. Additionally, errors that occur during the manufacturing process can also accumulate during installation. Therefore, after installing each unit or multiple units, the grid dimensions must be verified step by step, and records must be kept. If significant error accumulation is detected during truss installation that affects subsequent installation, installation must be halted, the cause analyzed, and corrective measures promptly implemented. For large-span trusses, when installing a single span, bolts should not be fully tightened in one go to allow for later adjustments due to error accumulation or inadequate scaffolding platform support causing bearing misalignment. Platform support height adjustments can be made using jacks, but the strength and stability of the scaffolding must be ensured.

Other precautions during the installation of bolted ball steel grid structures

First, during the handling of structural members, measures must be taken to prevent deformation caused by human factors and ensure proper protection of finished products. Second, it is essential to ensure the effective length of bolt insertion, check whether the set screws are fully seated in their slots, and verify that the set screws are fully engaged. This is particularly critical for space frames subjected to dynamic loads, as bolts are prone to loosening under prolonged dynamic loading conditions. Additionally, it is important to note that while welding connections between spheres and support plates at support locations are permitted as structural welded connections, any form of welding connection between dissimilar materials within the space frame is strictly prohibited. The installation of the space frame must be carried out on a reliable and effective installation platform. Utilize the installation platform and other conditions to ensure that compressed members are not subjected to compressive stress during installation. Verify grid dimensions during installation to prevent the accumulation of errors.

Bolted ball steel grid structures have high requirements for processing and installation accuracy. Therefore, we should focus on key steps during processing and installation to improve the safety and reliability of grid structures and eliminate quality and safety hazards at an early stage.

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