Quality control and safety management in Urumqi steel structure construction

Urumqi steel structure engineering is widely used in industrial plants, high-rise buildings, and bridge projects due to its advantages of high strength, light weight, and short construction period. However, steel structure construction is characterized by frequent high-altitude operations, complex welding processes, and high component hoisting risks. Its quality and safety management are directly related to the overall performance of the project and the life safety of construction personnel. This article discusses the quality control points and safety management strategies of steel structure projects from the perspective of the entire construction process, providing a systematic reference for engineering practice.

1. Quality and safety pre-control in the construction preparation stage

Construction preparation is the basis for ensuring the quality and safety of steel structure projects. The editor of Xinjiang Steel Structure said that in the technical preparation process, it is necessary to organize a joint review of design drawings, focusing on checking key parameters such as component size, node connection form, weld grade, etc., to ensure that the construction plan is consistent with the design intention. For example, a certain over-limit high-rise steel structure project used BIM technology to conduct 3D modeling and discovered three connection conflicts between steel columns and concrete core tubes in advance, thus avoiding rework during the construction phase. The "three inspection system" must be strictly implemented for the acceptance of materials on site. Steel, high-strength bolts, welding materials, etc. must provide factory certificates and mechanical property test reports, and conduct sampling retests in accordance with specifications. In a factory project, high-strength bolt connection nodes failed due to failure to detect the anti-slip coefficient, resulting in rework losses of 500,000 yuan. Such cases highlight the importance of material control.

Safety preparation cannot be ignored either. The editor of Xinjiang Steel Structure said that a special safety construction plan needs to be prepared before construction, and prevention and control measures should be formulated for dangerous sources such as high-altitude operations, hoisting, and temporary use of electricity. Operators must undergo level three safety education and training, and special operators (welders, crane workers, etc.) must hold certificates to work. At the same time, dangerous work areas need to be divided on site, warning signs must be set up, and qualified safety protection supplies such as fall arresters and fire blankets must be provided. In a bridge steel structure project, a worker fell from a height because edge protection was not installed in time. The lesson was profound.

2. Refined quality control in processing and production links

Factory processing of steel structure components in Urumqi is the core link of quality control. When cutting and blanking, CNC cutting equipment should be used to ensure dimensional accuracy. The vertical deviation of the cutting surface must be ≤0.05t (t is the plate thickness), and there must be no defects such as cracks and slag inclusions. The parameters of the welding process need to be determined through the welding process qualification (PQR). For example, when CO₂ gas shielded welding is used for Q355B steel, the welding wire diameter should be 1.2mm and the welding current should be controlled at 280-320A. For thick plate welding (plate thickness ≥30mm), preheating (preheating temperature 80-120°C) and post-heating hydrogen elimination treatment must be performed to prevent welding cold cracks. In a sports stadium pipe truss project, preheating requirements were not implemented, resulting in three cracks exceeding 20mm in length in the chord butt welds. Carbon arc gouging was eventually used for repairs, delaying the construction period by 15 days.

When assembling components, tooling fixtures must be used to ensure assembly accuracy. For example, the verticality deviation of steel columns should be ≤H/1000 (H is the column height) and not greater than 15mm. The Urumqi steel structure manufacturer said that the bolt connection surface needs to be sandblasted and rust removed, and the anti-slip coefficient test result should be ≥0.45 (friction surface treatment level Sa2.5). In addition, components need to undergo third-party testing before leaving the factory, focusing on component deformation, weld non-destructive testing (UT/MT), coating thickness (dry film thickness ≥ 80 μm) and other indicators. Unqualified components are strictly prohibited from leaving the factory.

3. Quality and safety collaborative management during on-site installation stage

The installation of steel structures must follow the principle of "bottom to top, layered and segmented". Unreasonable installation sequence can easily lead to structural instability. For example, when the steel frame of a boiler in a power plant was installed, it was not constructed in the order of "columns first, beams later to form a stable unit", and the top beams were installed first without authorization, causing three steel columns to become unstable and bent, causing direct economic losses of more than 2 million yuan. Before the hoisting operation, the lifting mechanical performance needs to be checked (for example, the rated lifting capacity of a 25t truck crane at a 10m amplitude is 8.5t). The setting of the lifting point should be determined through force calculation. The angle between the sling and the component should not be less than 60°. After the components are in place, they need to be temporarily fixed in time, such as using wind ropes (diameter ≥ 12mm) or temporary supports (double HW200×200 steel). The hooks can be loosened after a stable structural system is formed.

Safety management of high-altitude operations requires the implementation of "three treasures, four mouths and five edges" protection. Workers must wear double-hook safety belts and use them high and low. The Urumqi steel structure manufacturer said that scaffolding should be erected with full-floor scaffolding or cantilevered scaffolding. The scaffolding boards must be fully paved and fixed. The distance between poles should be ≤1.5m, and the distance between sweeping poles and the ground should be ≤200mm. Temporary power use requires "three-level power distribution and two-level protection". The ground resistance of the distribution box is ≤4Ω. Power tools must use Class II handheld tools and be equipped with leakage protectors (action current ≤30mA, action time ≤0.1s). During the construction of the steel structure of an office building, an electrician was electrocuted because the mobile distribution box was not grounded, and the project was suspended for rectification.

4. Quality traceability and risk prevention and control in the acceptance and operation and maintenance stages

The acceptance of steel structure sub-projects needs to be carried out in stages, including the acceptance of foundations and foundations, main structures, roofing projects and other sub-segments. During acceptance, it is necessary to check hidden engineering records (such as anchor bolt embedding deviations, weld repair records), inspection reports (such as steel structure deformation detection, high-strength bolt final tightening torque detection), functional tests (such as anti-slip coefficient test, roof water spray test) and other information. For example, during the acceptance inspection of the steel structure roof of an airport terminal, it was found that the final tightening torque of 12 M20 high-strength bolts did not meet the standard (design torque 600N·m, measured low value 480N·m), and the steel structure roof passed the acceptance after being re-tensioned.

After the project is delivered, a steel structure health monitoring system needs to be established to monitor key node stresses (using fiber Bragg grating sensors), structural displacement (accuracy 0.1mm), ambient temperature and other parameters in real time. The Urumqi steel structure manufacturer said that the coating condition should be checked regularly during the operation and maintenance phase. When the damaged area of ​​​​the coating reaches 10%, anti-corrosion repairs must be carried out and high-pressure airless spraying should be used to recoat to ensure that the total thickness of the coating is not less than the design value. Due to a long-term lack of maintenance on a steel structure pipe gallery in a chemical plant, the coating failed, causing the steel components to be corroded to a depth of 2 mm, and the bearing capacity was reduced by 30%. In the end, 20 beams had to be replaced, and the maintenance cost exceeded 3 million yuan.

5. Innovative application of digital technology in quality and safety management

BIM technology can realize the full life cycle management of steel structures. By comparing the BIM model with on-site measured data (3D laser scanning point cloud), it can realize the visualization of component installation deviations (for example, in a project, it was found through point cloud comparison that the steel truss installation deviation is as large as 35mm, and it can be adjusted in time to meet the specification requirements). IoT technology can be used for smart helmet positioning (UWB positioning accuracy 10cm), remote monitoring of lifting machinery torque limiters, and automatic power cutoff and alarm when the crane is overloaded. The AI ​​visual monitoring system can identify violations such as not wearing a safety helmet and throwing objects at high altitudes, with a recognition accuracy of more than 95% and a response time of <3 seconds. After an EPC project applied a smart construction site platform, the timely rate of rectification of safety hazards increased from 65% to 92%, and the incidence of common quality problems dropped by 40%.

Conclusion

The quality control and safety management of steel structure construction in Xinjiang is a systematic project that needs to run through the entire PDCA cycle of "planning-implementation-inspection-disposal". By strengthening construction preparation, refined processing and production, coordinated installation management and control, full-cycle acceptance operation and maintenance, combined with the innovative application of digital technology, the goal of "zero defects in quality and zero safety accidents" can be achieved. In the future, with the development of modular construction, intelligent welding robots and other technologies, steel structure engineering management will move towards a more efficient and intelligent direction, providing solid support for the industrial upgrading of construction.