TB/T 2349-2016 in English

Core changes in the standard revision

Detailed explanation of key technical requirements

1. Specimen preparation specifications

The standard requires that the specimens must maintain the three same principles: same material (chemical composition, mechanical properties), same process (welding/connection process), same stress field (local stress state). Special specimens such as cylindrical head weld nails must meet the requirement of height-to-diameter ratio ≥4.

2. Key parameters of testing machine

• Dynamic force calibration: must comply with GB/T 25917 repeatability error ≤±1%
• Coaxiality deviation: JJG 556-2011 stipulates ≤5%
• Safety monitoring: cycle counter error <0.1%

3. Fatigue curve establishment method

Linear regression under double logarithmic coordinates:
lgN = A - mlgΔσ
The correlation coefficient |γ| must be greater than the value specified in Table 1 (such as γ_min=0.707 when n=8), otherwise additional test data is required.

Implementation suggestions

Background of standard evolution

With the complexity of the load spectrum of high-speed railway bridges, the 2016 version adds variable amplitude loading and special environment simulation requirements. Compared with international standards (such as EN 1993-1-9), my country's standards are more detailed in the classification of welded joints, but lack multi-axial fatigue test clauses.