GB/T 33363-2016Hot-dip galvanized steel strand for prestress (English PDF)

7.2.3 Requirements for relaxation test

Use 70% of the nominal breaking force of the hot-dip galvanized steel strand as the initial force of the relaxation test. The duration of the relaxation test shall be 1000h. On the basis of ensuring the 1000h relaxation qualified, the test value of the shorter period of at least 120h may also be used to estimate the relaxation value of 1000h.

7.2.4 Other special requirements

After the negotiation between the supplier and the purchaser, the galvanized steel strands with other special requirements can be supplied.

7.2.5 Slanting tension coefficient

For the hot-dip galvanized steel strand used for general purpose, its slanting tension coefficient shall be no greater than 28%.

For the hot-dip galvanized steel strand used for cables, its slanting tension coefficient shall be no greater than 20%.

7.2.6 Fatigue performance

7.2.6.1 The hot-dip galvanized steel strand for general purpose shall not break after being applied a load of 2 million times 0.7Fm~(0.7Fm~2 delta Fa). The fatigue stress amplitude shall be calculated as per the Formula (1):

Where:

Sn - nominal cross-sectional area of the hot-dip galvanized steel strand, in mm2;

2 delta Fa - load value of the fluctuating stress amplitude, in N.

7.2.6.2 The hot-dip galvanized steel strand for cables shall not break after being applied a load of 2 million times 0.45Fm~(0.45Fm~2 delta Fa). The fatigue stress amplitude shall be calculated as per the Formula (2):

Where:

Sn - nominal cross-sectional area of the hot-dip galvanized steel strand, in mm2;

2 delta Fa - load value of the fluctuating stress amplitude, in N. test is invalid, and shall take samples again to do the test.

8.1.2 Maximum force total elongation

8.1.2.1 Determination of maximum force total elongation, Agt, shall be carried out as per GB/T 21839; the gauge length is no less than 500mm.

8.1.2.2 The actual measurement may be performed by adding 1% of the yield elongation plus the percentage between elongation of the jaw spacing and the new spacing of the clamps.

8.1.3 Specified non-proportional extension force

8.1.3.1 Determination of the specified non-proportional extension force shall be carried out as per the provisions of GB/T 21839; the applied force, Fp0.2, when the non-proportional extension using the gauge length of the extensometer to reach the 0.2% gauge-length of the extensometer.

8.1.3.2 When the supplier performs the production inspection, the load, Ft1, may be measured, if the total extension reaches 1% original gauge length; if such value conforms to the provision of Table 2, the product can be delivered; however, the Fp0.2 shall be measured during arbitration.

8.1.4 Elastic modulus Measurement

of elastic modulus shall be carried out as per the provisions of GB/T 21839.

8.2 Relaxation test

8.2.1 The stress relaxation test of the steel strand shall be carried out as per the provisions of GB/T 21839.

8.2.2 The galvanized layer on the sample surface at the clamping part of the anchorage shall be cleaned with dilute acid before test; and corrosion of the steel base shall be avoided.

8.3 Slanting tension test

The slanting tension test shall be carried out as per the provisions of GB/T 21839.

8.4 Fluctuating tensile fatigue test

The fluctuating tensile fatigue test shall be carried out as pe the provisions of GB/T 21839. […]

8.5 Zinc layer weight