How is the performance of aluminum curved roof trusses

Welded nodes have a significant impact on the performance of aluminum alloy curved roof trusses, specifically in terms of material properties, structural stiffness and durability:

1. Changes in the mechanical properties of materials

When welding aluminum alloys (such as 6061-T6), the heat-affected zone (HAZ) will coarsen grains due to high-temperature annealing, and the strength will be reduced by about 15%-30%. For example, the tensile strength of the T6 aluminum alloy base material is about 260MPa, and the strength of the heat-affected zone may drop below 180MPa after welding. In particular, if there is a welded joint in the chord of the arc truss, stress concentration is likely to occur in the HAZ when it is bent. In addition, welding residual stress may cause microcracks in the component, accelerating fatigue failure under long-term wind load or vibration.

2. Loss of structural geometric accuracy and stiffness

The surface accuracy of the curved truss is crucial to the stress state. Welding deformation may cause the arc deviation to exceed the allowable range (usually ≤L/2000, L is the span). For example, if the arch height deviation of a 100-meter span truss exceeds 50mm after welding, the support reaction force will be offset and the lateral bending moment will increase. At the same time, the sudden change in local stiffness at the node welding will change the overall vibration frequency of the truss, which may cause the risk of wind vibration resonance. A convention and exhibition center once had a 12% deviation between the truss frequency and the design value due to the chord welding error. Finally, the wind resistance requirements were met through node reinforcement and adjustment.

3. Weakened corrosion resistance and durability

The destruction of the oxide film in the aluminum alloy welding area will reduce the corrosion resistance. Especially in coastal or industrial environments, if the weld is not anodized or sealed, electrochemical corrosion may occur. Studies have shown that the corrosion rate of untreated welded nodes in salt spray environments is 2-3 times that of the parent material. In addition, defects such as weld porosity and slag inclusions will accelerate stress corrosion cracking. After 5 years of use, cracks appeared at the welded nodes of a coastal gymnasium. Inspection found that it was intergranular corrosion caused by chloride ion penetration.

Improvement measures

Use bolted connections or mechanical connections instead of welding (such as fisheye joints, cast aluminum nodes) to avoid strength loss in the heat-affected zone;

Use TIG inert gas shielded welding for key nodes, control the heat input, and perform artificial aging treatment (such as 175℃×8h) after welding to restore strength;

The surface of the welding area is subjected to secondary oxidation treatment or coated with an anti-corrosion coating to enhance corrosion resistance;

Finite element analysis is used to optimize node form and reduce stress concentration.

In summary, improper handling of welding nodes will significantly affect the performance of aluminum alloy curved trusses, and risks need to be avoided from multiple dimensions including process selection, quality control and post-maintenance.

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