August 21, 2026 Bolted connections are one of the most important details in steel structure construction. A well-designed steel building still depends on correct on-site installation, especially when ordinary bolts and high-strength bolts are used for structural connections.
Improper hole correction, wrong washer orientation, uncontrolled tightening torque, or an incorrect tightening sequence can affect connection performance and create hidden safety risks. This guide summarizes the main requirements for steel structure bolting and the common mistakes that should be avoided during installation.
Fasteners commonly used in steel buildings include ordinary bolts, high-strength heavy hex bolts, torsion-shear high-strength bolts, blind rivets, self-tapping screws, and powder-actuated fasteners.
Ordinary bolts are often used as temporary installation bolts during assembly. Blind rivets, self-tapping screws, and powder-actuated fasteners are mainly used for secondary components such as metal roof panels, wall cladding, trims, and other non-primary structural parts.
For primary steel connections, high-strength bolts are typically required because they provide better bearing capacity and more reliable connection performance.
High-strength bolts used in steel structures generally include:
A high-strength heavy hex bolt assembly usually includes one bolt, one nut, and two washers. A torsion-shear bolt assembly usually includes one bolt, one nut, and one washer.
Using the correct bolt type and matching components is essential. Bolts, nuts, and washers should not be mixed randomly between different systems or specifications.
Before tightening high-strength bolts, the steel members should be properly aligned and the installation accuracy should be adjusted. High-strength bolts should not be used as temporary installation bolts.
If bolt holes need minor adjustment, gas cutting must not be used for hole enlargement. Reamers or files should be used instead. Gas cutting can damage the hole edge, affect the connection surface, and reduce the reliability of the joint.
Washer orientation is also important. For tension-control bolts, the nut side with the circular bearing surface should face the chamfered side of the washer. For heavy hex high-strength bolts, the chamfered side of the washer under the bolt head should face the bolt head, and the circular bearing surface of the nut should face the chamfered side of the washer.
High-strength heavy hex bolts are usually tightened by either the torque method or the turn-of-nut method.
When the torque method is used, the required installation torque should be calculated according to the project specification. Torque wrenches must be calibrated before use. The torque should be applied to the nut, and the tightening value should be controlled carefully during final tightening.
When the turn-of-nut method is used, the general installation process is:
Initial tightening
Initial tightening inspection
Marking
Final tightening
Final tightening inspection
Final marking
For large joints, a re-tightening step may be required between initial tightening and final tightening. The initial tightening torque is often set at about 50% of the final tightening torque, while the re-tightening torque is usually the same as the initial tightening torque.
Torsion-shear high-strength bolts should be tightened with a dedicated electric wrench. The installation normally includes initial tightening and final tightening. For large joints, re-tightening may also be added.
Final tightening is considered complete when the spline end of the bolt is sheared off. For bolts that cannot be tightened with the dedicated wrench due to limited working space, the torque method or turn-of-nut method may be used according to the applicable specification.
After initial tightening or re-tightening, nuts should be marked with color indicators. Initial tightening, re-tightening, and final tightening should be completed within the required time limit, commonly within 24 hours, to ensure consistent connection quality.
The tightening sequence directly affects how well the connected plates fit together. In general, high-strength bolt tightening should proceed from the area with the greatest joint stiffness toward the area with less restraint, and from the center of the bolt group outward.
For general joints, tightening should move from the center toward both ends. For H-section column butt joints, the flange bolts are usually tightened first, followed by the web bolts. When a bolt group includes both primary and secondary member connections, the primary member connection should normally be tightened first.
If a connection involves both high-strength bolting and welding, the usual construction sequence is bolting first and welding afterward, unless the design documents specify otherwise.
Several problems are common during steel structure bolting work:
Using high-strength bolts as temporary installation bolts
Enlarging bolt holes by gas cutting
Mixing bolts, nuts, or washers from different assemblies
Installing washers in the wrong direction
Skipping torque wrench calibration
Tightening bolts from the edge inward instead of from the center outward
Failing to mark bolts after initial tightening
Leaving too much time between initial tightening and final tightening
Using the wrong tightening method for the bolt type
Avoiding these mistakes helps improve installation quality, reduce rework, and protect the long-term safety of the steel structure.
Steel structure bolting may look simple, but it is a key part of construction quality control. Correct bolt selection, proper hole treatment, calibrated tools, washer orientation, tightening method, and tightening sequence all affect the final performance of the connection.
For steel buildings, warehouses, workshops, and industrial structures, careful bolting work helps ensure that the building frame performs as designed and remains reliable throughout its service life.
The most common fasteners include ordinary bolts, high-strength heavy hex bolts, torsion-shear high-strength bolts, blind rivets, self-tapping screws, and powder-actuated fasteners.
No. High-strength bolts should not be used as installation bolts. They should only be used after the component position and installation accuracy are properly adjusted.
Gas cutting is not allowed for hole enlargement. Reamers or files should be used instead to make minor corrections.
The torque method controls tightening by a calculated torque value, while the turn-of-nut method controls tightening by a specified rotation angle after initial tightening.
Correct washer orientation ensures proper bearing contact and helps the bolt assembly perform as intended. Wrong washer direction can affect tightening quality.
Tightening should generally proceed from the center of the joint outward, and from the area of greater stiffness toward the less restrained area.
Yes. Torque wrenches used for construction should be calibrated before use to ensure the torque value is accurate.
Because delayed tightening can affect joint consistency and connection quality. In many cases, the process should be completed within 24 hours.
Common mistakes include wrong washer orientation, hole enlargement by gas cutting, using the wrong tightening method, and skipping torque calibration.
It is a general reference for common bolting practices, but the actual construction requirements should always follow the project design documents and applicable specifications.
We will reply you within 24 hours. If for urgent case, please add WhatsApp/WeChat: +86 13791994562,. Or call +86 18766271397 or +86-532-81119695 directly.
*We respect your confidentiality and all information are protected.
We will only use your information to respond to your inquiry and will never send unsolicited emails or promotional messages.
