How can we safely and efficiently complete the installation of long-span steel truss structures?

Steel structures are increasingly used in modern construction projects, especially in buildings with special requirements for large spaces, long spans, and high headroom. Long-span steel truss structures, due to their unique structural system and excellent mechanical properties, have become the preferred structural form. Despite this, their installation and construction is a high-risk, high-tech, and highly coordinated systematic project. The construction process not only requires addressing complex procedures such as high-altitude work, component hoisting, and joint welding, but also requires strict control of construction quality and structural deformation. Therefore, developing a scientific construction organization plan, combined with advanced technology and refined management methods, is key to achieving high-quality delivery.

Key Points for Construction Quality Control
1. High-Strength Bolt Connection Quality Control
High-strength bolts are the primary connection method between steel truss members. Their construction quality directly impacts the overall load-bearing performance and safety of the structure. Therefore, the following key aspects should be carefully controlled:
Bolt Management and Protection: Bolts should be stored by model to avoid mixing. The storage environment should be moisture-proof, rust-proof, and contamination-resistant. After unpacking on-site, they should be used promptly and must not be mixed with old parts.
Friction Surface Treatment: Before installation, the friction surfaces of the connection must be thoroughly cleaned of oil, loose rust, welding slag, and other impurities to ensure a clean, dry contact surface with a sufficient friction coefficient. High-strength bolting should not be performed in rainy or snowy weather.
Proper Installation and Hole Position Correction: High-strength bolts should not be driven in by force. If they cannot be inserted smoothly into the hole, use a reamer or positioning tool to adjust the position. Do not forcefully drive them in.
Graded Tightening and Control Method: Bolts should be tightened using the "initial tightening + final tightening" method. Initial tightening force should be controlled within 60% to 80% of the designed pretension force. Final tightening should be performed using a torque wrench or shear wrench to ensure that the tightening force meets regulatory requirements.
Tightening Sequence Control: Bolts should be tightened sequentially from the rigid end to the free end to avoid local stress concentration and ensure overall structural stability.
2. Welding Process Quality Control
Welding is another critical construction process in connecting steel truss members. The quality of on-site welding is directly related to structural safety and the reliability of force transmission, so welding specifications must be strictly adhered to.
Process Selection and Operation Specifications: On-site welding is typically performed using manual arc welding and CO₂ gas shielded welding. Welding personnel must be certified and receive specialized technical briefings.
Welding Environment and Sequence Control: Weld preheating and post-heating measures should be implemented in low-temperature or high-humidity environments. Welding should be performed continuously, minimizing pauses that may cause stress concentration or weld defects. Weld Quality Inspection: Within 24 hours of welding completion, critical welds should be inspected using non-destructive testing methods such as ultrasonic, radiographic, or magnetic particle testing to ensure that welding quality meets design and specification requirements.
3. Measurement and Monitoring During Installation
Controlling the geometric form of the truss structure during construction is crucial, and measurement and monitoring management must be implemented throughout the entire process.
Pre-installation Re-measurement: Before installation begins, the axis position and elevation of each embedded component should be re-measured to ensure consistency with the designed position and that deviations are within the allowable range.
Real-time Structural Attitude Monitoring: During the hoisting and splicing process, the deflection changes, column verticality, and overall displacement of the truss should be regularly measured and compared with the design parameters. Any problems identified should be corrected promptly.
Member Deformation Observation: Deformation monitoring should be performed on key components such as main members and support members. If abnormal bending or localized twisting is detected, construction should be suspended immediately to investigate the cause and implement reinforcement or replacement measures before continuing.

Main Construction Methods
Different structural forms and site conditions determine the choice of truss installation process. Currently, there are three main installation methods:
1. Segmented Hoisting
The segmented hoisting method is the most commonly used construction method. The overall truss structure is divided into several segments. After pre-assembly on the ground, each segment is hoisted to the designed location and assembled in mid-air.
Advantages: Relatively low construction equipment requirements, strong adaptability, and suitable for projects with average site conditions.
Disadvantages: Significant overhead work and high installation precision requirements require precise measurement and positioning equipment.
2. Overall Hoisting
This method assembles the entire truss structure or large module on the ground and then uses large hoisting equipment to lift it to the designed height in one go.
Advantages: High assembly precision, easily controlled welding quality, and significantly reduced overhead work time.
Disadvantages: Requires a large ground work area, requires high lifting equipment capacity, and construction risks are concentrated in the hoisting process.
3. High-Area Sliding or Jacking
The high-altitude sliding method is suitable for ultra-long-span steel structure projects. The entire structure is assembled on the ground or on a supporting platform, then moved or lifted into place using hydraulic jacks and track slides.
Advantages: Low overhead work intensity and high installation safety.
Disadvantages: Technical complexity, long construction period, and high requirements for the design of the temporary support system.

Safety and Organizational Management Guarantees
To ensure the safe and efficient installation of large-span steel truss structures, it is necessary to simultaneously strengthen safety management and organizational coordination at the construction site:
Developing a specialized construction plan: Develop a specific construction organization design for each installation method, clearly defining the lifting path, assembly sequence, safety measures, and emergency response plans.
Strengthening Personnel Training and Certification: Key positions, especially those working at heights, welders, and hoisting operators, require both technical and safety training.
Setting Up Temporary Support and Platform Systems: Before installation, temporary supports or platforms should be installed based on force analysis to prevent structural instability before a stable system is established.
Ensuring Safety Monitoring Throughout the Construction Process: Establishing a dual "technical + safety" supervision mechanism, with full inspections and documentation of key steps such as lifting, assembly, and welding.

The installation and construction of large-span steel truss structures is a highly integrated and systematic engineering and technical activity, involving multiple disciplines such as structural mechanics, construction technology, and safety management. To achieve a balance between structural performance and construction efficiency, a systematic approach must be implemented from design preparation, process selection, quality control, and safety assurance. With the continuous advancement of construction technology and the accumulation of engineering practice, the efficient and safe construction of steel truss structures will become more mature and standardized, providing solid structural support for the sustainable development of large-scale public buildings in my country.