When the external environment or internal structure temperature changes, the chimney anticorrosion will deform.

Chimney corrosion has the property of thermal expansion and contraction. When the external environment or the internal temperature of the structure changes, the chimney corrosion may deform. If the deformation is constrained, stress will be generated within the structure. When this stress exceeds the tensile strength of the chimney corrosion, temperature cracks will form. In some large-span bridges, temperature stress can reach or even exceed load stress. The main distinguishing feature of temperature cracks compared to other cracks is that they expand or close with temperature changes. The primary construction factors causing temperature changes include:

Hydration heat. During the construction process, after the large-scale chimney anti-corrosion (thickness exceeding 2.0 meters) is cast, the internal temperature becomes very high due to the heat released during cement hydration, resulting in a significant temperature difference between the inside and outside, which causes cracks to appear on the surface.

Secondly, improper construction measures during steam curing or winter construction can lead to rapid temperature changes in the chimney's anti-corrosion process, with uneven internal and external temperatures, making cracks more likely to occur.

Thirdly, during the installation of cross bracing in prefabricated beams, and when welding the pre-buried steel plates for supports and leveling plates, improper welding procedures can easily lead to burn and cracking of the anti-corrosion coating near the ironwork. When tensioning prestressed components using the electric heating method, the temperature of the prestressed steel can rise to very high levels, making the anti-corrosion components of the chimney prone to cracking as well.

Preparation for groundbreaking.

(1) Review the engineering project management system of the factory, communicate with each other to establish normal working relationships with the technical department and quality assurance department.

(2) Review the factory's quality control plan and, in collaboration with the technical and quality assurance departments, determine the actual quality inspection items, quality control checkpoints, and supervision acceptance procedures for this project.

(3) Agreed with the technical and quality assurance departments on the content and format of various quality inspection reports for this project.

(4) Review material warranty certificates to determine the content of material re-inspection; participate in material re-inspection tests. Examine decorative material warranty certificates.

(5) Inspect the warehouse receiving and dispatching system for materials.

(6) Review and approve welding process qualification task documents or welding process qualification transfer reports submitted by factories.

Participate in the welding process qualification test.

Review welding qualifications and valid documents.

(9) Review the qualification and certification validity of non-destructive testing (NDT) personnel and relevant equipment.

(10) Review the certification validity period of length measuring instruments for engineering purposes.

(11) Inspect the condition of the rust removal and painting equipment to ensure they meet the relevant technical requirements and that their product quality meets the specifications of the technical conditions.

(12) Assisted the owner in reviewing and signing the construction start order.

2.2 Production Implementation Phase.

2.2.1 Structural Supervision.

Sample quality inspections include sketches, prototypes, samples, and cutting situations; quality checks of small panels and T-shaped beam combinations (panel photography), followed by a visa after inspection; quality inspections of U-shaped steel processing; inspections of web, top, and bottom plate dimensions, bevel cutting quality, and bottom plate corner rolling; marking inspection for assembled components of web, top, and bottom plates; inspection of the assembly jig (外形, section lines, slope), followed by a visa; quality inspection of segmented positioning and assembly; post-welding segmented disassembly, slope condition of assembly interfaces at various construction sites, and flatness of plate edges; re-inspection of the factory-submitted segmented inspection report data, with visa approval.

2.2.2 Welding Supervision. ① Routine Inspections: During the welding process, the welding supervisor intensifies routine inspections, ensuring proper use of welding materials, adequate pre-welding preparations, compliance with welding process conditions, workers' valid certifications, and appropriateness of welding specifications. ② Weld Seam Quality Supervision: For butt welds, general surface quality inspections and certifications are conducted for Class 1 and 2 welds; full penetration welds are sampled; and for lap welds, sampling is also performed.

2.2.3 Non-destructive Testing Supervision: Review the types and lengths of non-destructive testing for various welds to ensure they meet technical requirements; specify RT (X-ray filming) and verify if the RT inspected areas comply with technical specifications; authenticate RT inspection reports; examine UT (ultrasonic testing) reports; upon the client's request or by engaging a third party, review some welds as necessary.