Construction and Quality Requirements for Bolted-Welded Hybrid Connections in High-Rise Steel Structures

Bolted-welded hybrid connections are a common structural configuration for beam-to-column joints. To ensure the load-bearing capacity and seismic performance of high-rise steel structures, construction and acceptance processes must meet a series of technical requirements.

 

I. Material Compatibility Requirements

 

High-strength bolts and welding materials used in high-rise steel structures must be compatible. Bolts typically utilize strength grades of 10.9 or 8.8, with matching nuts and washers supplied from the same batch. Welding materials must match the strength of the base metal; for instance, E50-type electrodes may be used with Q345 steel to avoid imbalances where the weld is stronger than the base metal, or vice versa.

 

II. Construction Sequence Requirements

 

The construction of bolted-welded hybrid connections in high-rise steel structures must adhere to the principle of "bolting before welding." High-strength bolts are installed and tightened to both initial and final torque levels before flange welding is performed. This sequence prevents the loss of bolt pretension caused by welding heat and ensures clearly defined load paths within the joints.

 

 

III. Bolted Connection Requirements

 

Bolt holes must be formed by drilling; enlarging holes via gas cutting is strictly prohibited. During installation, friction surfaces must be kept dry and clean, free from oil or rust. Final tightening torque is calculated according to specifications; for torque-shear bolts, the shearing off of the spline (spline-end) indicates proper tightening. Within a single joint, bolt tightening must proceed symmetrically from the center outward to prevent warping of the plate assembly.

 

IV. Welding Quality Requirements

 

Flange groove welds must achieve full penetration, and non-destructive testing (NDT) may only be conducted 24 hours after welding. Ultrasonic testing must cover at least 20% of the welds, and any defects exceeding permissible limits require rectification. During welding, measures such as symmetrical welding and interpass temperature control are implemented to minimize angular distortion and shrinkage stress. 

 

V. Acceptance and Inspection Requirements

 

Upon completion of construction for each story of a high-rise steel structure, spot checks shall be conducted on the bolt torque and weld appearance of bolted-welded hybrid joints. The inspection rate for bolt torque shall be no less than 5%, and weld surfaces must be free from defects such as cracks, porosity, and slag inclusions. For joints in critical areas of the high-rise steel structure, magnetic particle testing or liquid penetrant testing may be additionally performed to ensure the safety and reliability of the connections.