Typical Defects and Damage in Long-Span Bolted Spherical Node Steel Space Structures

 1. Bolted Spherical Node Defects

Threaded Hole Machining Accuracy Issues

The threaded holes in bolted spherical nodes are critical components where machining precision is paramount. In actual production, issues such as positional deviations and uneven pitch frequently occur. For instance, excessive positional deviation can result in loose connections between bolts and spheres, preventing effective load transfer and degrading structural performance.

Uneven pitch impedes bolt insertion and tightening, leading to insufficient preload. In large-span space frames, this may cause node loosening and compromise overall structural stability.

Bolt Sphere-Member Connection Issues

Bolt spheres typically connect to members via bolted joints. In practice, bolt length, diameter, and tightening torque all affect connection quality. Insufficient bolt length compromises the connection's integrity, increasing the risk of disengagement under external forces.

Excessive or insufficient tightening torque also compromises reliability. Excessive torque may deform or even fracture the bolt, while insufficient torque fails to ensure adequate preload, causing joint loosening.

2. Member Defects

Member Deformation

In large-span steel space structures, members may deform due to various factors. For instance, transportation impacts or compression can cause localized member deformation. During installation, improper construction practices may subject members to excessive external forces, causing deformation.

Member deformation compromises the structure's overall load-bearing capacity, reducing member strength. Severe deformation may also disrupt connections between members, jeopardizing structural stability.

Member Corrosion

Steel space frame structures are typically exposed to natural environments, making members susceptible to corrosion. Corrosion is particularly severe in humid or acidic environments. It causes rust formation on member surfaces, diminishing strength and durability.

Corrosion also degrades member aesthetics and service life. In severe cases, it may lead to member failure, jeopardizing overall structural safety.

3. Structural System-Wide Defects

System-Wide Deformation

Large-span bolted spherical steel space frames may experience systemic deformation during prolonged service. This may result from inadequate structural design, substandard construction quality, or external loading factors. For instance, significant wind loads or seismic forces can induce structural deformation.

Overall structural deformation impairs normal functionality and reduces load-bearing capacity. Additionally, deformation may cause uneven stress distribution within the structure, further accelerating structural deterioration.

Loosening of Structural Connections

Loosening of bolted spherical joints is a common defect in large-span steel space frame structures. Due to the complexity of these joint connections, bolts may gradually loosen during prolonged use. This results in inadequate joint integrity, compromising the structure's overall stability and integrity.

Loose structural connections may also intensify structural vibrations. In extreme cases, this could potentially trigger structural collapse.

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