Tower Crane Structural Test Methods per GB/T 17807-1999
GB/T 17807-1999, "Tower Cranes — Structural Test Methods," is a dedicated standard for testing the steel structures of tower cranes. It specifies test procedures for crane steel structures—including the tower mast, boom, balance arm, and slewing platform—covering strain measurement, deflection measurement, stress analysis, and structural strength evaluation to verify the safety and reliability of the structural design.
Test Methods and Procedures
The standard defines test methods including stress testing, static load test, dynamic load test, and stability test. Stress testing uses resistance strain gauges placed on critical cross-sections of load-bearing members—mid-span of the tower main chord, critical sections of the boom's upper and lower chord members, and the connection points of the slewing tower. At 100% rated load, the stress at each measuring point must not exceed the allowable stress of the material. Measuring points should also be placed in the heat-affected zones of critical weld seams.
The selection and bonding quality of strain gauges directly affect the accuracy of stress testing. Measuring points should be located in areas of maximum structural stress—the mid-section of the tower main chord, the variable cross-sections of the boom's upper and lower chords, and around the connection bolt holes of the slewing tower. For weld heat-affected zones, place gauges on the base metal side, 2–3 mm from the weld toe. Before bonding, the surface must be ground smooth and cleaned with acetone; allow at least 24 hours for the adhesive to cure before starting the test.
Data acquisition for stress testing should be recorded at five load levels: no-load, 25% load, 50% load, 75% load, and 100% load. Hold each condition steady for at least 30 seconds before recording. Plotting the load-stress curve reveals whether the structure remains in the elastic deformation range. The deviation between measured and calculated stress values should be within ±15%.
Load Test Requirements
Static load test—lift 1.25 times the rated load in the most unfavorable direction and hold for 10 minutes; after unloading, residual deformation must not exceed 20% of the maximum elastic deformation. Dynamic load test—operate at 1.1 times the rated load through 3 combined-motion cycles; the brake must engage reliably and all mechanisms must function normally. Stability test—under the most unfavorable working condition, outrigger reaction must be ≥0 (for mobile cranes) or the stability coefficient must be ≥1.4 (for fixed-base cranes).
100% load
Residual ≤20%
Reliable braking
Coefficient ≥1.4
Weld heat-affected zones
Basis for conclusions
| Test Item | Load | test method | Judgment |
|---|---|---|---|
| Stress Test | 100% | strain gauge Measurement | ≤allowable stress |
| static load | 1.25Times | Hold10min | Residual≤20% |
| dynamic load | 1.1Times | 3Cycle | Braking Reliability |
| Stability | Maximum radius | outrigger reaction | ≥0 |
The static load test is the core procedure for verifying the structural strength of a tower crane. The test is performed in the most unfavorable orientation—with the boom positioned at a 45° angle to the tower mast diagonal—and lifts 1.25 times the rated load in that direction. Once the load is fully lifted, it is held in position for 10 minutes while a theodolite measures horizontal displacement at the top of the tower mast and deflection at the boom tip. After unloading, the structure is inspected for permanent deformation and cracks.
Static Load Test Report
The test report must include the test plan (measurement point layout, load chart, and test procedure), test data (stress and deflection values under each operating condition, plus load-deflection curves), and a results analysis section comparing calculated versus measured values with a safety margin assessment. The conclusion should clearly state whether the crane passed or failed, supported by the corresponding evidence.
| Measurement Point Location | Measurement Point Type | Purpose | Quantity |
|---|---|---|---|
| tower main chord | strain gauge | Stress Measurement | ≥4 |
| Boom Upper/Lowerchord member | strain gauge | Stress Measurement | ≥4 |
| Slewing Tower mast | strain gauge | Stress Measurement | ≥2 |
| Weld Seam Heat-Affected Zone (HAZ) | strain gauge | Welding Stress | ≥2 |
Kelude Heavy Industry offers tower crane structural testing services in accordance with the applicable standard.
FAQ
Q: Where are strain gauges placed during a tower crane structural test?
A: Resistance strain gauges are mounted on critical cross-sections of the primary load-bearing members — the mid-span of the tower main chords, the critical sections of the boom's upper and lower chord members, and the slewing tower connection points. Additional gauges are placed in the heat-affected zones of major weld seams. At 100% load, the stress at every measuring point must remain within the allowable stress.
Q: What loads and acceptance criteria apply to the static and dynamic load tests?
A: For the static load test, the crane lifts 1.25 times the rated load in the most unfavorable direction and holds it for 10 minutes. The residual deformation must not exceed 20% of the maximum elastic deformation. For the dynamic load test, the crane operates at 1.1 times the rated load through three complete cycles, during which all mechanisms must function normally and braking must be reliable.
Q: What are the requirements for the stability test?
A: For a fixed-base tower crane, the stability coefficient must be ≥ 1.4 under the most unfavorable operating conditions, and the outrigger reaction must remain ≥ 0. After wind anchoring, the anti-overturning stability coefficient must be ≥ 1.2.
Q: What does the structural test report include?
A: The test report covers the test plan (including the strain gauge layout diagram and load chart), test data (stress and deformation values for each operating condition, plus load-deformation curves), result analysis (a comparison of calculated versus measured values and a safety margin assessment), and a conclusion stating whether the crane passed or failed, along with the supporting evidence.
