GB/T 50459-2017 in English

1. Project classification and grading

According to the type of obstacles, crossing projects are divided into Class A (navigable rivers/electrified railways/highways) and Class B (non-navigable obstacles). According to the total span and main span length, they are divided into three grades: large (≥300m/150m), medium (100-300m/50-150m), and small (≤100m/50m).

2. Key Technical Requirements

2.1 Structural Design

• Deformation control: mid-span deflection of main beam ≤L/400, horizontal displacement of steel tower ≤H/200
• Stress calculation: the pipeline needs to verify the circumferential stress (σ_h=pd/2δ), axial stress (σ_a=0.5σ_h+M/W) and equivalent stress (σ_e=√(σ_x²+σ_y²-σ_xσ_y+3τ²))

2.2 Seismic design

3. Materials and anti-corrosion specifications

Special requirements: The anti-corrosion level of the crossing pipeline shall not be lower than that of the line pipeline, and the steel wire rope shall be hot-coated with neutral anti-corrosion materials.

4. Implementation suggestions

1. During the construction of the suspension cable crossing, 100% non-destructive testing of the main cable strands shall be carried out
2. A three-level health monitoring system (warning threshold 5%/20%/95%) shall be set up for navigable river crossing
3. The compensator installation shall be welded under the optimal temperature difference conditions, and the pre-stretching amount ΔL=La(t_1-t_0)