1.What is the relationship between coating thickness and wind pressure resistance?
The function of the coating: The main functions of the coating (primer, topcoat, backcoat) on pre-coated steel coils are to provide corrosion resistance, weather resistance, color, and aesthetics. Its thickness is extremely thin (measured in micrometers, 1 millimeter = 1000 micrometers), and its mechanical strength is negligible in resisting the enormous stress generated by wind loads.
The main body resisting wind pressure: The strength against wind pressure comes entirely from the "steel plate substrate" and the "supporting structure" behind it. You can think of pre-coated steel coils as a "sandwich," where the coating is just the outermost thin layer of "pigment" or "cling film," and the actual load-bearing components are the inner "metal sheets" (substrate) and the subsequent "skeleton" (purlins, frame).
2.What impact do the mechanical properties of steel plate substrates have on wind pressure resistance?
Substrate thickness: This is the most important factor. It's usually measured in millimeters (mm), such as 0.5mm, 0.8mm, etc. The greater the thickness, the greater the moment of inertia of the cross-section, and the stronger the resistance to bending and deformation.
Steel yield strength: This refers to the strength grade of the material itself, such as Q235, Q345, G550 (yield strength 550MPa), etc. High-strength steel can withstand greater loads at the same thickness.
Substrate type: Hot-dip galvanized (GI), aluminized zinc (AZ), etc., mainly affect corrosion resistance, and also have a slight impact on strength (the standard strength of steel sheets varies depending on the coating).
3.What are the effects of plate design and cross-sectional shape on wind pressure resistance?
Wave height and rib height: The profiled sheet (e.g., high-wave sheet, low-wave sheet) has different cross-sectional properties. Higher rib height can greatly increase the section modulus of the sheet, thus providing stronger bending and compressive strength. This is similar to folding a flat sheet of paper into corrugated paper, which dramatically increases its load-bearing capacity.
Rib density and shape: Denserly designed, scientifically sound reinforcing ribs can effectively distribute stress and prevent localized deformation.
4.What is the weak, indirect correlation between coating thickness and wind pressure resistance?
Corrosion Protection: Sufficiently thick and high-quality coatings (such as high-performance topcoat + thick-coated substrate) can effectively protect the steel substrate from rust for a long time. Once the substrate thins due to corrosion or develops rust pits, its effective load-bearing cross-section decreases, and its mechanical properties (strength and stiffness) decline over time, thus compromising its initial wind pressure resistance.
Therefore, in highly corrosive environments (such as coastal areas and industrial zones), choosing a more corrosion-resistant coating system (such as thick coating + PVDF topcoat) is crucial to ensure that the substrate's mechanical properties do not degrade due to corrosion throughout the building's entire lifespan, thereby maintaining its long-term wind pressure resistance.
5.How to determine the core parameters?
Substrate material and thickness: e.g., "Aluminized zinc-plated steel sheet AZ150, substrate thickness 0.8mm".
Steel strength: e.g., "Yield strength ≥550MPa".
Plate type and rib height: e.g., "Angle-saddle type III-420, rib height 68mm".
Purlin spacing design: e.g., "Maximum purlin spacing 1.5m".
Coating system selection criteria: Coating thickness (e.g., "Two coats and two bakings on the front, topcoat thickness ≥20μm") and type (e.g., "PVDF fluorocarbon coating") should be determined based on the project's corrosion environment, color durability requirements, and design service life, and should be treated separately from structural wind pressure calculations.