When choosing the pipe diameter of the arch supports of the tunnel greenhouse used in the courtyard, what factors should be taken into consideration?

When choosing the pipe diameter of the arch supports of the tunnel greenhouse used in the family garden, multiple factors need to be systematically considered. The core of this is to find the best balance among safety, durability and cost.

I. Key Considerations (Determining Factors)
1. Geographical location and climatic conditions (Most important!)
This is the primary basis for choosing the pipe diameter and wall thickness.

Wind Load:

• Wind-prone areas (coastal, plains, mountainous regions): Greater wind resistance is required. The wind will cause uplift and shear forces on the greenhouse. Therefore, it is necessary to select thicker and wider pipes (for example: Φ32mm x 1.2mm).
• Windless areas (inland, urban courtyards): The requirements can be appropriately lowered, but still need to meet the basic safety standards.

Snow Load:

• Snowy areas: The accumulated snow acts as a significant static pressure, which may directly collapse the greenhouse. The pipe diameter and wall thickness must be strengthened, and a round-arch roof (which facilitates the sliding of snow) should be preferred over a flat roof.
• Snow-free areas: The main concern is the issue of wind resistance.

2. Dimensions and Span of the Greenhouse

• Span (Width): This is the most direct influencing factor. The larger the span, the higher the strength requirements for the arch members.  ≤ 4 meters span: Consider using a pipe diameter of Φ25mm.  4-meter span: It is strongly recommended to use pipes with a diameter of 32mm or larger.
• Height: An increase in height will enlarge the wind exposure area and thus require a stronger structure.
• Length (Length): The length has little impact, but the longer greenhouse requires a greater number of longitudinal braces to ensure overall stability.

3. Types of covering materials

The weight of the covering material is directly borne by the arch beam.

• Glass: The heaviest, therefore a very sturdy frame must be used (such as 40x40mm square tubes with a wall thickness of ≥ 1.5mm).
• PC solar panel / endurance board: Medium weight. Requires precision and strength of the frame (recommended: Φ32mm x 1.0mm or above).
• Plastic film: The lightest in weight, exerting the least pressure on the framework. The choice is mainly based on considerations of resisting snowstorms.

4. Steel material and anti-corrosion process (affects lifespan)

• Material: Prefer galvanized steel. Absolutely avoid using ordinary carbon steel that is prone to rust (even painted steel is not acceptable).
• Surface treatment (sorted by durability):

     Hot-Dip Galvanized: The best choice. The zinc coating is thick, with strong corrosion resistance, and the service life can reach 10-15 years. It is a must-have for outdoor use.
     Electro-galvanizing: The zinc layer is thin, has moderate rust prevention ability, has a short lifespan, and is not recommended.
     Painting / Applying anti-rust paint: The anti-rust effect is the poorest. Regular maintenance is required. It can generally be used once.

II. Structure and Other Factors (Supportive but Crucial)

5. Arch Spacing

• The smaller the spacing between the arch members (e.g. 0.65 meters), the better the overall stability. The strength requirement for a single arch member can be slightly reduced.
• The larger the spacing (for example, 1.0 meter), the thicker and stronger single arch rods must be used to make up for it.

6. Overall Structure Design

• A good greenhouse is not just about the arches. The number and strength of "longitudinal tension rods" (horizontal supports, diagonal braces, gutters) are equally crucial. They connect each arch together to form a stable spatial entity, effectively preventing distortion and deformation. A solidly constructed framework will also have a robust tension rod system.

7. Budget

• The larger the pipe diameter, the thicker the wall thickness, and the higher the galvanization standard, the more expensive the price will be.
• Key concept: One should not only consider the initial price, but also evaluate the "total cost of ownership". A more expensive greenhouse that lasts for 10 years is much more cost-effective than a cheaper one that rusts and breaks down after only 2 years.