The correct installation method of steel structure bolts

In modern building and bridge engineering, steel structure bolts, as the "joints of the metal framework", their installation quality directly determines the stability of the overall structure. This article will systematically introduce the standardized installation process of high-strength bolts (including friction type and pressure-bearing type), and provide practical solutions for construction teams in combination with common problems in engineering practice.

1. Preparatory Work: Accurate to the millimeter starting point

Material acceptance

Check the match between the performance grade of the bolts (such as 8.8S, 10.9S) and the warranty certificate

Randomly inspect the diameter tolerance of the screw using a vernier caliper (allowing a deviation of ±0.02mm)

Confirm the integrity of the anti-rust coating on the gasket

Contact surface treatment

Sandblasting rust removal to Sa2.5 grade standard (surface roughness 40-80μm)

The anti-slip coefficient test of the friction surface should be completed within 72 hours (≥0.45 is qualified).

Tool calibration

Electric torque wrenches need to be calibrated daily (with an error controlled within ±3%).

Prepare the initial tightening with an impact wrench (set the torque value to 50% of the final tightening)

2.Six-step standardized installation process

Step 1: Try on the matching holes

Fix the connection plate with temporary punching nails (the number of punching nails ≥ 15% of the number of bolt holes)

When inserting bolts, forced knocking is strictly prohibited. If the hole diameter deviation exceeds 1mm, reaming and remaking are required

Step 2: Initial tightening and positioning

Twist in the order of radiation from the center to the periphery

The scratch marking method is adopted to prevent missed tightening (as shown in Figure 1)

Step 3: Finally tighten and secure

The torque method for large hexagon head bolts: final tightening torque = coefficient k× design preload value × bolt diameter

The qualified standard for torque-shear bolts is the fracture of the plum blossom head

Step 4: Re-check and re-tighten

The inspection should be completed within 4 hours after the final tightening

Conduct torque spot checks on randomly selected 10% of bolts using a calibration wrench

Step 5: Anti-corrosion sealing

Apply molybdenum disulfide anti-corrosion grease to exposed threads

The gaps between the node plates are filled with sealant

Step 6: Process documentation

Establish a traceable file including the batch number of the bolts, the tightening personnel, and the inspection data

3. Solutions to Common Problems

Hole position deviation: Reamers are preferred for hole trimming, and flame reaming is strictly prohibited

Construction on rainy days: Set up rain shelters to ensure that the moisture content of the friction surface is no more than 8%

Delayed final tightening: If the final tightening is not completed within 24 hours, a new initial tightening is required

4. Direction of Technological Innovation

Intelligent torque control system (real-time upload of tightening data to the BIM platform)

Phased array ultrasonic testing technology for bolt preload

Self-sensing bolts (with built-in optical fiber sensors for monitoring stress changes)