During the construction phase of a steel structure factory building construction, the preload accuracy of high-strength bolt connections is a core element in ensuring structural safety and stability. Insufficient preload may lead to loosening of the connection, while excessive preload may cause bolt breakage or component deformation. Therefore, systematic construction control and quality inspection methods are necessary to ensure accuracy.
Before construction, the quality of high-strength bolts and connectors must be strictly controlled. The material and specifications of the bolts must meet design requirements. Upon arrival at the site, the manufacturer's certificate of conformity, quality certificate, and batch markings should be checked, and their tensile strength, yield strength, and other performance indicators should be verified through sampling inspection. The dimensional accuracy, hole diameter matching, and surface flatness of the connecting plates must meet the specifications to avoid uneven preload transmission due to component processing errors. Simultaneously, the treatment of the friction surface is a critical factor affecting preload accuracy. Sandblasting, shot blasting, or wire brush grinding methods should be used according to design requirements to remove oil, rust, and dust, ensuring that the surface roughness meets the standards, thereby improving the anti-slip coefficient.
The selection and control of the tightening process is a core aspect of ensuring preload accuracy. The main tightening methods for high-strength bolts include the torque method, the angle method, and the torque-shear method. The appropriate method must be selected based on the bolt type, specifications, and construction conditions. The torque method controls the preload by controlling the tightening torque. A calibrated torque wrench must be used, and its accuracy should be checked regularly to avoid preload deviations due to tool errors. The angle method controls the preload by rotating the nut to a specific angle. Accurate measurement of the initial and final tightening angles is required, ensuring a tight fit between the bolt and the connecting parts. The torque-shear method is suitable for torque-shear type high-strength bolts. Preload control is achieved by breaking off the bolt head; it is simple to operate and has high accuracy, but the performance of the electric wrench must be ensured to be stable.
The operational procedures during construction directly affect the accuracy of the preload. Construction personnel must receive professional training and be familiar with the tightening process requirements and quality control points to avoid preload loss or deviation due to improper operation. Tightening should follow the principles of symmetry and step-by-step tightening. Initial tightening should be performed first to eliminate gaps between the plates, followed by final tightening to achieve the designed preload. For large nodes or complex connections, a grouped symmetrical tightening method should be used to reduce uneven preload caused by localized stress concentration. Simultaneously, the tightening speed must be controlled to avoid bolt overheating due to rapid tightening, which could affect preload stability.
Environmental factors have a significant impact on preload accuracy. Temperature changes cause bolt material to expand and contract, affecting the preload value. Therefore, preload adjustments are necessary when working in low- or high-temperature environments. Excessive humidity can lead to corrosion of friction surfaces, reducing the anti-slip coefficient; therefore, moisture-proof measures must be taken to ensure the connection surfaces are dry. Furthermore, external factors such as wind and vibration can affect the stability of tightening tools; windproof and vibration-damping measures must be implemented during construction to ensure a smooth tightening process.
Quality inspection and acceptance are the final line of defense for ensuring preload accuracy. After construction, a comprehensive inspection of the bolt connection is required, including appearance quality, tightening marks, and preload testing. Preload testing can be conducted through sampling or full-scale testing. The actual preload of the bolts is measured using equipment such as ultrasonic force gauges and torque sensors, and compared with the design value. Bolts that fail the test must be replaced or retightened promptly until the accuracy requirements are met. Simultaneously, a quality traceability mechanism must be established to record the installation time, operator, and test results for each bolt for subsequent maintenance and management.
Construction management and personnel training are the long-term foundation for ensuring preload accuracy. Construction units must establish a comprehensive quality management system, clearly defining the key quality control points and responsible persons for each stage to ensure a standardized and orderly construction process. Furthermore, regular technical training and assessments should be organized for construction personnel to improve their operational skills and quality awareness, avoiding preload deviations caused by human factors. Through systematic construction control and quality testing methods, the preload accuracy of high-strength bolt connections during the steel structure factory building construction phase can be effectively guaranteed, providing a solid guarantee for structural safety and stability.
