Steel structure engineering bolt connection inspection requirements are essential to ensure the safety and stability of the entire structure. The fastener connections between steel members must be tightly secured against the connecting plates, with a neat and uniform appearance. Before any permanent tightening is performed, an inspection must be conducted to confirm compliance. Bolts are classified into 11 grades: 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among these, bolts rated at 8.8 or higher are considered high-strength bolts, while those below 8.8 (excluding 8.8) are classified as ordinary bolts.
During installation, the number of temporary bolts used at each joint should be determined based on the load applied during construction. It is required that no fewer than one-third of the total holes are filled with temporary bolts, and at least two temporary bolts must be used per connection. This ensures structural stability during the assembly process.
For permanent ordinary bolt connections, it is not allowed to use more than one washer at a single end. Additionally, large nuts cannot replace washers. All bolts must be securely tightened, with at least two exposed threads visible after tightening. For bolts that are designed to be loose, anti-loosening measures such as double nuts or spring washers should be used. Manual methods like applying thread-locking compounds can also be employed for bolts that are exposed.
In cases where bolted connections are subjected to dynamic loads or are part of critical structural components, spring washers should be used as specified in the design. Spring washers must be placed on one side of the nut. When working with I-beams or channel sections, it is recommended to use inclined washers to ensure the nut and bolt head make perpendicular contact with the supporting surface.
Proper storage and transportation of fasteners are crucial to maintain their integrity. Fasteners should be stored in a dry, clean environment, protected from moisture, rain, and dust. They should be organized by type and size. Handling should be done carefully to avoid damage to packaging or threading. Any remaining fasteners should be properly recycled and stored for future use.
Regarding the specifications for bolts and nuts in steel structures, all types, sizes, and performance characteristics of high-strength bolts, ordinary bolts, nuts, and washers must comply with current national standards and design specifications. A full inspection is required for all components.
The inspection method includes checking the quality certificate, Chinese marking, and test report of the materials. The torque coefficient of high-strength large hex bolt connection pairs, the tightening force of torsion-shear type bolts, and the minimum tensile load of ordinary bolts must be re-inspected according to national standards. Eight bolts per specification should be tested, and the results should be verified through re-inspection reports.
For high-strength large hex bolt connections, a visual and tactile inspection is conducted. At least 10% of the bolts per node should be checked, with a focus on torque testing. Each bolt is tapped with a small hammer weighing 0.3 to 0.5 kg to check the tightness. If any connection does not meet the standard, an additional 10% of the bolts should be inspected. If issues persist, the entire node should be re-tightened and rechecked. Torque checks should be performed one hour after installation and completed within 24 hours.
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