Resistance to dynamic loads
Cyclic and fatigue test
Resistance of reinforcing steel to dynamic loads is of particular importance for structures subjected to such loads, such as all engineering objects, industrial objects, as well as buildings located in seismic and mining areas.
EPSTAL steel is tested for dynamic load resistance in two types of tests. According to the requirements of the standard PN-H-93220:2018-02 for the species B500SP a cyclical and fatigue test is carried out.
This test consists of alternating compression and stretching of the sample by axial force within a predetermined range of stresses and deformations. A positive test result is obtained when, after reaching a predetermined number of load cycles, the sample will not be exposed to any visible scratches or cracks.
Cyclic test parameters for B500SP grade are specified in PN-H-93220:2018-02. The load cycling frequency should be between 0.5 and 3 Hz, the deformation ε of 1.5 to 4% (depending on the nominal diameter of the sample and the measured length as the machine handle), while the minimum number of load cycles is 5. Grade B500SP is the only one tested for dynamic load resistance within all reinforcing steel grades available in Poland.
This test consists in subjecting the sample to axial stretching in the stress range up to 300 MPa with variable sinusoidal force. The amplitude value is 175 MPa for d ≤ 25 mm and 160 MPa for d> 25 mm. The frequency does not exceed 200 Hz. A positive test result, as in the case of a cyclic test, is obtained when, after loading the sample with the set minimum number of load cycles, it will not suffer any damage visible to the naked eye. For B500SP steel, the minimum number of fatigue load cycles is 2 million.