The test stress spectrum of the maximum tensile stress of the midspan section of the main beam under 13 working cycles is shown in the table.
| Series | Stress amplitude/MPa | Frequency |
| 1 | 77.5 | 1 |
| 2 | 72.5 | 4 |
| 3 | 67.5 | 8 |
| 4 | 62.5 | 1 |
| 5 | 37.5 | 1 |
| 6 | 32.5 | 2 |
| 7 | 27.5 | 1 |
| 8 | 22.5 | 7 |
| 9 | 17.5 | 4 |
| 10 | 12.5 | 4 |
| 11 | 7.5 | 54 |
This result indicates that the fatigue life of the main girder structure of the 260t-27m casting crane bridge in a steel plant should reach 468990 working cycles. The equipment was put into use in 2007. It is estimated that the annual operation is 360 d and the daily operation is 84 full loads. By December 2020, 423360 work cycles have been completed.
From 2021, the remaining fatigue life of the main beam is 45630 working cycles. If the daily workload increases to 100 full loads, the remaining working time will be 456 working days until April 2022. After April 2022, the metal structure of equipment will enter a period of increasing potential safety hazards.
It should be noted that the significance of the fatigue life estimation technology is to prompt the time period or window period from safe use of equipment to the frequent occurrence of hidden dangers. Local repair welding may delay the extension time of damage and failure without changing the inevitable process of damage and failure.