1. Foundation Design and Construction
The stability of photovoltaic bracket systems relies on foundations adapting to geological conditions. Designs include independent bases (concrete foundations) or pile-driven bases, with strict control over elevation tolerance (±5mm) and bolt embedding accuracy. Construction requires using “settlement observation points” to monitor subsidence, with post-construction settlement not exceeding “tilt/deflection” limits. For pile foundations, verticality deviation must be <1%, and concrete strength ≥C30 after curing ≥7 days. For slope installations, anti-slide piles or ground anchors prevent soil displacement, with pile depth verified dynamically.
Key Specifications:
- Independent bases use “concrete + embedded bolts” with “foundation elevation” per GB50797.
- Pile foundations require verticality <1% and concrete curing ≥7 days.
- Slope sites employ anti-slide piles/anchors (e.g., grouted rock bolts).
2. Bracket-to-Foundation Connection
Connections must resist wind uplift and shear forces, using pre-embedded bolts or post-installed anchors. Base plates should avoid uneven contact (gap ≤0.5mm under full load). Bolt tensioning follows torque specifications (e.g., M12 anchor tension ≥45kN·m), with base plate leveling shims ≤50mm and anti-corrosion treatments.
Key Specifications:
- Use “expansion anchors + leveling shims” (e.g., M12 anchor tension ≥45kN·m).
- Base plate leveling shims ≤50mm, with galvanization or epoxy coating.
3. Bracket Structure and Components
Bracket materials include hot-dip galvanized steel (e.g., Q235, thickness ≥2mm) or aluminum alloy (e.g., 6063-T6). Components must withstand dead loads, wind loads (0.5–1.0 kN/m²), and snow loads (0.6–1.2 kN/m²), with deflection ≤L/250 (L=span). Purlin spacing is 3–4m, and vertical deflection ≤2m under maximum wind/snow.
Key Specifications:
- Steel: Q235 with zinc coating ≥85μm; aluminum: 6063-T6, thickness ≥2.5mm.
- Load standards: GB50009 for wind/snow loads.
- Deflection limit: L/250; purlin spacing 3–4m.
4. Corrosion Protection and Durability
Steel components use “hot-dip galvanizing + paint” (e.g., zinc coating ≥85μm, paint thickness ≥60μm), while aluminum employs anodizing (film thickness ≥10μm). Coastal sites require 316 stainless steel or enhanced coatings. Avoid direct contact between dissimilar metals to prevent galvanic corrosion.
Key Specifications:
- Steel: “Galvanizing + paint” (zinc ≥85μm, paint ≥60μm).
- Aluminum: Anodizing (film ≥10μm).
- Coastal areas: 316 stainless or class C5 protection.
5. Connection and Fastening Systems
Bolted connections use grade 8.8 bolts for main structures and 4.8 for secondary elements. Torque control (e.g., M10 bolt: 35–40N·m) and anti-loosening measures (e.g., spring washers) are critical. Welded connections require V-groove welds with throat thickness ≥0.7×plate thickness, using E4303 or E5015 electrodes. NDT (e.g., UT) ensures weld integrity ≥98%.
Key Specifications:
- Bolts: 8.8-grade for primary connections; torque as per specs.
- Welds: Throat thickness ≥0.8×plate thickness; CO₂ gas shielding for uniformity.
6. Load and Safety Compliance
Design loads follow GB50797 (e.g., 1.3×roof live load). Wind/snow zones dictate specific coefficients (1.2–1.5). Bracket spacing aligns with module dimensions, avoiding asymmetric loading. “Point load distribution” ensures uniform stress via purlins and bolts.
Key Specifications:
- Live load: 1.3×standard value (e.g., 0.75kN/m² roof load).
- Wind/snow: Zone-based coefficients (1.2–1.5).
- Load distribution: “Purlins + bolts” for even force transfer.
7. Inclination and Orientation
Tilt angles (20°–25° optimal) impact energy yield. Avoid shading with spacing ≥1.5×module height in winter. Orientation follows “solar azimuth + tilt” calculations, with deviation ≤15° from true south. Anti-theft measures (e.g., welded brackets) enhance security.
Key Specifications:
- Tilt: 20°–25° for max irradiance.
- Spacing: ≥1.5×module height to prevent shading.
- Orientation: True south ±15°.
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