During winter construction of steel structures, a winter construction plan should be developed based on the requirements for winter construction of steel structures, and corresponding requirements should be adopted for the use of materials, personnel, etc.
- Due to the influence of the thermal expansion and contraction performance of materials during winter construction, the shortening of components caused by temperature should be fully considered during construction, and the method of adjusting deviations should be adopted for handling during construction. It is better to reserve a shortening allowance when cutting the components, and the welding shortening and compression deformation should be coordinated with the shortening deformation of the steel below zero degrees Celsius.
- The exposed welding rod used under negative temperature shall not exceed 2 hours, and if it exceeds 2 hours, it shall be re baked, and the number of times the welding rod is baked shall not exceed 3 times.
- When the ambient temperature is below 0 ℃, water-based coatings shall not be used for the coatings used in steel structures, and a coating process test shall be conducted before applying anti-corrosion coatings. During coating, rust, oil stains, burrs and other substances on the surface of the components must be cleaned up, and the surface must be kept dry. Painting operations shall not be carried out on snowy days or when there is thin ice on the components.
- When assembling components, rust, burrs, soil, oil stains, ice, snow, and other debris left within 50mm of the joint should be removed, and the joint should be confirmed to be dry and free of residual moisture.
- When welding steel plates over 9mm below zero degrees Celsius, multi-layer welding should be used. The weld seam should be welded layer by layer from bottom to top, and each weld seam should be welded in one go. If the welding is interrupted, the welding defects should be removed before welding again. It is strictly prohibited to strike an arc on the welding base material.
- When installing steel structures on site, protective shelters should be erected in case of snow or wind speeds above 6m/s.
- During winter transportation and stacking of steel structures, anti slip measures are adopted, and the stacking site for components is flat, solid, and free of water pits, with no ice on the ground. When stacking components of the same type, the components should be kept horizontal, and the shims should be placed on the same straight line to prevent the components from slipping.
- When installing high-strength bolt joints, the conflicting surfaces of the components must not have snow or ice, and must not come into contact with dirt, oil, or other contaminants.
- During winter welding, the preheating range before welding should be expanded to twice the plate thickness (1.5 times the plate thickness at room temperature); Electric heating should be preferred as the heating method to ensure uniform heating in the preheating area and avoid local overheating of the base material. Preheat with 2-4 gas burners, with preheating zones on both sides of the weld bead. The width of each side should be greater than twice the thickness of the weld and should not be less than 100 mm. The preheating temperature should be measured with a temperature measuring pen at a distance of 50 mm from the center of the weld seam, and welding operations can only be carried out after reaching the specified temperature.
- Develop a reasonable post heating system, adopt emergency post welding insulation and slow cooling measures for plate thickness t<40 mm, and adopt emergency post welding and insulation slow cooling measures for plate thickness t ≥ 40 mm, with a post heating temperature of 200-300 ℃. This measure can slow down the cooling rate of the weld seam and help diffuse hydrogen escape.
